case study fracture neck of femur

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• Published: 28 January 2009

Bilateral femoral neck fractures in an adult male following minimal trauma after a simple mechanical fall: a case report

• Asheesh Sood 1 ,
• Christopher Rao 2 &
• Ian Holloway 1  

Cases Journal volume  2 , Article number:  92 ( 2009 ) Cite this article

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Despite being rare there are several reports in the medical literature of bilateral femoral neck fractures in adult patients. They have been reported to have occurred following major trauma, or as a result of primary or secondary bone disease. In this case report we describe for the first time in the literature bilateral femoral neck fractures in a patient following minimal trauma after a simple mechanical fall.

Case presentation

We describe the case of an 84-year-old gentleman who sustained bilateral intracapsular fractures following a simple mechanical fall. Prompt diagnosis and early surgical intervention resulted in a satisfactory outcome.

This case highlights that in the elderly, even in the absence of primary and secondary bone disease, bilateral neck of femur fractures can occur following relatively minor trauma. Consequently, the orthopaedic surgeon, emergency physician and general practitioner should be aware of this injury, particularly when managing traumatic injuries in confused patients.

Bilateral fractures of the Neck of the Femur (NOF) have been reported to have occurred following major trauma, or as a result of primary or secondary bone disease. We describe the case of an 84-year-old gentleman who sustained bilateral intracapsular fractured NOF following a simple mechanical fall. Early diagnosis, resuscitation, surgical intervention, post-operative mobilisation and discharge; according to best practice guidelines [ 1 ]; resulted in a satisfactory outcome.

Following a review of the published literature we undertake to discuss the importance of prompt diagnosis and early surgical treatment in achieving a satisfactory outcome following this injury. Finally, we aim to discuss the implications of this case on our routine orthopaedic practice.

An 84-year-old gentleman presented to the Accident and Emergency Department in the early hours of the morning after a mechanical fall down three stairs. He was an active, independent gentleman with no significant co-morbidities. He was also the full time carer for his wife who suffered from multiple sclerosis. His pre-morbid mobility was good and he did not require any walking aids.

He was immediately resuscitated in the Accident and Emergency Department. Clinical examination revealed external rotation of both legs and pain on passive movement of both hips. X-ray of his pelvis showed completely displaced intracapsular hip fractures on both sides [Figure 1 ].

Anterioposterior radiograph of the pelvis showing bilateral completely displaced intracapsular fractures of the neck of femur .

The fractures were treated by cemented hemiarthroplasty using Thompson prostheses. This was undertaken with the patient in the supine position within 24 hours of admission using an antero-lateral approach by two senior Orthopaedic surgeons [Figure 2 ]. He had a satisfactory post-operative recovery and was able to mobilise and fully weight-bear within 2 days of the surgery.

Anterioposterior radiograph of the pelvis showing bilateral fractures of the neck of femur treated by cemented Thompson hemiarthroplasties .

Simultaneous bilateral NOF fractures are rare. They are however, several reports in the medical literature of bilateral NOF fractures occurring as a result of primary or secondary bone disease. For example, hypocalcemia [ 2 ], osteomalacia [ 3 ], osteoporosis, renal osteodystrophy [ 4 ], radiotherapy [ 5 ] and multiple myeloma. Bilateral NOF fractures have also been reported to have occurred following persistent, sustained stress [ 5 ].

Uncomplicated trauma is a rare cause of bilateral fractured NOF [ 6 ]. There have been reports of bilateral NOF fractures after seizures secondary to epilepsy, drugs, and electrocution [ 6 ]. Intracapsular fractures of the NOF prior to the fifth decade of life usually result from severe injury [ 5 ]. Konforti et al [ 7 ] described bilateral NOF fractures in a 37-year-old gentleman crushed during a mining accident. Carrell et al [ 8 ] described the case of an 8 year old boy who sustained a bilateral neck fractures following a 25 foot fall. More recently Gunal et al [ 9 ] describe bilateral traumatic NOF fractures.

In the case we describe an otherwise fit and well gentleman who sustained bilateral NOF fractures following a low energy injury fall down three stairs. This is a common mechanism of injury which often leads to a unilateral NOF fracture. It is important to note that this patient gave a definite history of a fall which led to the injury in contrast to fatigue fractures [ 5 ] where patients describe their leg giving way followed by pain. Bilateral fractured NOF have been reported in the literature in the elderly following minimal trauma [ 10 ]. However, in this case described the patient had a background of corticosteroid induced osteoporosis, gross obesity and rheumatoid arthritis.

Guidelines for the management of hip fractures recommend that surgical intervention should be carried out within 48 hours of the fracture occurring [ 1 ]. As well as causing distress to the patient, delay in surgery is associated with increased morbidity and mortality, and a reduced chance of success and rehabilitation [ 11 ]. Surgery should be performed as soon as the medical condition of the patient allows, provided that appropriate staffing and facilities are available [ 11 ]. However, it has also been demonstrated that surgical treatment conducted as night-time emergency cases are associated with increases mortality [ 11 ].

Our management of this patient was entirely consistent with these guidelines. The fractures were diagnosed early and the patient was resuscitated appropriately. The patient was reviewed by the physicians and anaesthetists on the day of admission and optimized medically. Both hip fractures were managed by simultaneous cemented hemiarthroplasty within 24 hours of admission on a day-time trauma list. McBryde et al [ 12 ] have demonstrated the safety of simultaneous hip arthroplasties, albeit in the context of elective surgery. The operation was performed in the supine position, to avoid repositioning the patient, in order to shorten the total operating time. There is however, no evidence to support the superior efficacy of any position and we feel the surgeon should use the position with which he is most comfortable.

All hip injuries presenting to the Accident and Emergency Department in our hospital have an anterioposterior radiograph of the pelvis with both hips included as part of initial assessment. This is an important precaution as there may be an injury of the opposite hip which could easily be missed. As a result of this case, our junior surgical staff have been trained to be particularly vigilant to the possibility of bilateral NOF fractures, particularly in the very elderly, in cases where there may be primary or secondary bone disease, when the mechanism of injury is high-impact or unknown, and when patients are confused and unable to localize pain.

In this case report we present a rare combination of injuries occurring simultaneously in an elderly gentleman. While a unilateral hip fracture is a very common injury managed appropriately on a regular basis by Orthopaedic surgeons, bilateral injuries of this nature presenting simultaneously can prove to be a diagnostic and therapeutic challenge. Early recognition and prompt surgical intervention can lead to good outcomes despite the severity of this injury. Bilateral anterioposterior radiographs should be taken as a matter of routine in patients presenting with suspected fractured NOF and orthopedic staff should be vigilant to the possibility of bilateral NOF fractures.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

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Northwick Park Hospital, Watford Road, Harrow, Middlesex, HA1 3UJ, UK

Asheesh Sood & Ian Holloway

Department of Biosurgery and Surgical Technology, Imperial College London, 5 Cheerytree House, Droop Street, London, W10 4EL, UK

Christopher Rao

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Authors' contributions

AS and CR were responsible for drafting the case study. IH was responsible for revising it critically for important intellectual content and was the consultant ultimately responsible for managing this patient. All authors have made substantial contribution to the conception of this case report, read and approved the final version to be submitted.

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Sood, A., Rao, C. & Holloway, I. Bilateral femoral neck fractures in an adult male following minimal trauma after a simple mechanical fall: a case report. Cases Journal 2 , 92 (2009). https://doi.org/10.1186/1757-1626-2-92

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DOI : https://doi.org/10.1186/1757-1626-2-92

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• Renal Osteodystrophy
• Minimal Trauma
• Intracapsular Fracture
• Full Time Carer
• Cement Hemiarthroplasty

Cases Journal

ISSN: 1757-1626

Impacted neck of femur fracture

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Citation, DOI, disclosures and case data

At the time the case was submitted for publication Martin Saenz Aguirre had no recorded disclosures.

Presentation

Referred for left hip pain and walking inability following a fall in the street.

Patient Data

An impacted left subcapital neck of femur fracture is suspected on the frontal X-ray of the pelvis. 

Metalic post-embolization material is seen in the pelvis secondary to a previous hemorrhage years ago.

Coronal CT images demonstrate the presence of an impacted fracture in the subcapital region of the left femur. There is neither bone fragment displacement nor loss of the articular congruence.

Post-processed color-coded VNCa bone marrow map, superimposed on the calcium images, shows bone marrow edema in the same location of the fracture.

Frontal X-ray of the pelvis after surgical fixation of the fracture.

Case Discussion

Bone marrow edema detection is one of the many potential applications of the Dual-energy CT 1 .

Bone marrow edema detection can be useful in the search of occult fractures, especially in the emergency setting when MRI is not available.

In this case, the fracture was already visible on the conventional X-ray and non-contrast CT images. Nonetheless, bone marrow edema is nicely depicted on post-processed color-coded VNCa images and shows a perfect spacial correlation with the fracture location.

• 1. Gosangi B, Mandell JC, Weaver MJ et-al. Bone Marrow Edema at Dual-Energy CT: A Game Changer in the Emergency Department. (2020) RadioGraphics. 40 (3): 859-874. doi:10.1148/rg.2020190173 - Pubmed

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Displaced Femoral Neck Fractures

A Case-Based Approach

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• John T. Gorczyca 0

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• A case-based approach to the diagnosis and management of displaced femoral neck fractures
• Discusses the current evaluation, science, techniques and common complications
• A practical and user-friendly guide for orthopedic and trauma surgeons, residents and fellows

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Similar content being viewed by others, tips and tricks for orif of displaced femoral neck fractures in the young adult patient.

An overview on the treatment strategies of non-displaced femoral neck fracture in the elderly

Femoral Neck Fractures in the Elderly

• Anterolateral approach
• Aseptic necrosis
• Displaced femoral neck fracture
• Garden classification
• Hemiarthroplasty
• Hip osteoarthritis
• Pauwels classification
• Symptomatic hardware
• Total hip arthroplasty (THA)

Table of contents (9 chapters)

Front matter, displaced femoral neck fractures in young healthy patients: the evaluation.

• Kyle T. Judd

Displaced Femoral Neck Fractures in Young Healthy Patients: The Science

• Megan R. Terle, Robert P. Dunbar Jr

Displaced Femoral Neck Fractures in Young Healthy Patients: The Technique

John T. Gorczyca

Treatment of Displaced Femoral Neck Fractures with Hemiarthroplasty

• Robert Bruce Simpson, John T. Gorczyca

Treatment of Displaced Femoral Neck Fractures with Total Hip Arthroplasty

• Gillian L. S. Soles, Alexander Greenstein

How to Sort Out the Controversies in Displaced Femoral Neck Fractures

• Cecilia Rogmark

Complications with Displaced Femoral Neck Fractures: Aseptic Necrosis

• Benjamin F. Ricciardi, John T. Gorczyca

Complications with Displaced Femoral Neck Fractures: Symptomatic Hardware

Complications with displaced femoral neck fractures: nonunion, back matter, editors and affiliations, about the editor, bibliographic information.

Book Title : Displaced Femoral Neck Fractures

Book Subtitle : A Case-Based Approach

Editors : John T. Gorczyca

DOI : https://doi.org/10.1007/978-3-030-84444-8

Publisher : Springer Cham

eBook Packages : Medicine , Medicine (R0)

Copyright Information : The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022

Softcover ISBN : 978-3-030-84443-1 Published: 16 October 2021

eBook ISBN : 978-3-030-84444-8 Published: 15 October 2021

Edition Number : 1

Number of Pages : XI, 192

Number of Illustrations : 120 b/w illustrations, 33 illustrations in colour

Topics : Orthopedics

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Femoral Neck Fractures

• Femoral neck fractures are common injuries to the proximal femur associated with increased risk of avascular necrosis, and high levels of patient morbidity and mortality.
• Diagnosis is generally made radiographically with orthogonal radiographs of the hip.
• Treatment is generally operative with open reduction and internal fixation versus arthroplasty depending on the age of the patient, activity demands and pre-injury mobility. 
• increasingly common due to aging population
• women > men
• Caucasians > African Americans
• United states has highest incidence of hip fx rates worldwide
• femoral neck is intracapsular, bathed in synovial fluid
• lacks periosteal layer
• callus formation limited, which affects healing
• high energy in young patients
• low energy falls in older patients
• 6-9% associated with femoral neck fractures
• treat femoral neck first followed by shaft
• normal neck shaft-angle 130 +/- 7 degrees
• normal anteversion 10 +/- 7 degrees
• major contributor is medial femoral circumflex (lateral epiphyseal artery)
• some contribution to anterior and inferior head from lateral femoral circumflex
• some contribution from inferior gluteal artery
• small and insignificant supply from artery of ligamentum teres
• displacement of femoral neck fracture will disrupt the blood supply and cause an intracapsular hematoma (effect is controversial)

• slight pain in the groin or pain referred along the medial side of the thigh and knee
• pain in the entire hip region
• no obvious clinical deformity
• minor discomfort with active or passive hip range of motion, muscle spasms at extremes of motion
• pain with percussion over greater trochanter
• leg in external rotation and abduction, with shortening
• traction-internal rotation AP hip is best for defining fracture type
• cross-table lateral
• full-length femur
• consider obtaining dedicated imaging of uninjured hip to use as template intraop
• helpful in determining displacement and degree of comminution in some patients
• helpful to rule out occult fracture
• not helpful in reliably assessing viability of femoral head after fracture
• rule out DVT if delayed presentation to hospital after hip fracture
• may be considered in some patients who are non-ambulators, have minimal pain, and who are at high risk for surgical intervention
• nondisplaced transcervical fx
• Garden I or II in the physiologically elderly
• achieve reduction to limit vascular insult
• reduction must be anatomic, so open if necessary
• female sex associated with increased reoperation rate 
• basicervical fracture
• sliding hip screw biomechanically superior to cannulated screws (may not be clinically superior)
• consider placement of additional cannulated screw above sliding hip screw to prevent rotation
• controversial
• debilitated elderly patients
• metabolic bone disease
• decreased intraoperative and postoperative fracture rates in elderly insufficiency fractures
• improved short and medium term mobility 
• older active patients
• more predictable pain relief and better functional outcome than hemiarthroplasty
• Garden III or IV in patient
• reduction method and quality has more pronounced effect on healing than surgical timing
• improved outcomes in medically fit patients if surgically treated less than 4 days from injury
• preoperative echocardiograms have been shown to delay the time to surgery without any effect on treatment decisions
• no difference in postoperative delirium, mortality or ambulatory function at 60 days 
• degree of displacement
• physiologic age of the patient (young is
• ipsilateral femoral neck and shaft fractures
• three screws if noncomminuted (3 screw inverted triangle shown to be superior to two screws)
• 1-inferior screw along calcar
• 2-posterior/superior screw
• 3-anterior/superior screw
• obtain as much screw spread as possible in femoral neck
• inverted triangle along the calcar (not central in the neck) has stronger fixation and higher load to failure
• clear advantage of additional screws not proven in literature
• starting point at or above level of lesser trochanter to avoid fracture
• avoid multiple cortical perforations during guide pin or screw placement to avoid development of lateral stress riser
• 10cm skin incision made beginning just distal to ASIS
• incise deep fascia
• develop interval between sartorious and TFL
• external rotation of thigh accentuates dissection plane
• LFCN is identified and retracted medially with sartorius
• identify tendinous portion of rectus femoris, elevate off hip capsule
• open capsule to identify femoral neck
• used to gain improved exposure of lower femoral neck fractures
• skin incision approx 2cm posterior and distal to ASIS, down toward tip of greater trochanter
• incision curved distally and extended 10cm along anterior portion of femur
• develop interval between TFL and gluteus medius
• anterior aspect of gluteus medius and minimus is retracted posteriorly to visualize anterior hip capsule
• capsule sharply incised with Z-shape incision
• capsulotomy must remain anterior to lesser trochanter at all times to avoid injury to medial femoral circumflex artery
• worse outcomes with displacement > 5 mm (higher rate of osteonecrosis and nonunions)
• no consensus on which reduction approach is superior
• multiple closed reduction attempts are associated with higher risk of osteonecrosis of the femoral head
• evacuate hematoma
• place A to P k-wires into femoral neck/head proximal to fracture to use as joysticks for reduction
• insert starting k-wire (for either cannulated screw or sliding hip screw) into appropriate position laterally, up to but not across the fracture
• once reduction obtained, drive starting k-wire across fracture
• insert second threaded tipped k-wire if adding additional fixation
• permit dynamic compression at fx site during axial loading
• prominent implants
• affects biomechanics of hip joint
• lower physical function on SF-36
• decreased quality of life
• anatomic reduction with intraop compression and placement of length stable devices decrease shortening
• posterior approach has increased risk of dislocations
• anterolateral approach has increased abductor weakness
• cemented also associated with lower rates of postoperative periprosthetic femur fractures
• unipolar vs. bipolar
• should consider using the anterolateral approach and selective use of larger heads in the setting of a femoral neck fracture
• improved functional hip scores and lower re-operation rates compared to hemiarthroplasty and internal fixation
• about five times higher than hemiarthroplasty
• incidence of 10-45%
• recent studies fail to demonstrate an association between time to fracture reduction and subsequent AVN
• AVN can still develop in nondisplaced injuries
• nonanatomical reduction
• reported by the FAITH study
• major symptoms not always present when AVN develops
• > 50% involvement then treat with FVFG vs THA
• prosthetic replacement (hemiarthroplasty vs THA)
• increased incidence in displaced fractures
• no correlation between age, gender, and rate of nonunion
• varus malreduction most closely correlates with failure of fixation after reduction and cannulated screw fixation.
• can be done even in presence of AVN, as long as not severely collapsed
• turns vertical fx line into horizontal fx line and decreases shear forces across fx line
• indicated in young patients with a viable femoral head
• indicated in older patients or when the femoral head is not viable
• also an option in younger patient with a nonviable femoral head as opposed to FVFG
• revision ORIF
• about seven times higher than hemiarthroplasty
• 46% failure with fixation techniques
• 8% failure with arthroplasty techniques
• failure rate approx. 2-4%, respectively
• overall failure rates still higher in fixation vs. arthoplasty at 10-year follow-up
• displaced femoral neck fractures
• basicervical femoral neck fractures
• current smokers
• decreased mortality, post-operative complications, time to surgery, length of stay (though conflicting results on length of stay)
• improved post-operative mobility at 4 months
• important to mitigate risks of hospital delirium which may lead to increased length of stay
• Normal TUG is <12 seconds in all age groups
• Persistent use of ambulatory aids is predicted if TUG > 26 seconds
• age >80 years
• ASA class >1
• prior walking aid use
• current tobacco use
• implant placement quality
• nondisplaced fracture
• not requiring revision surgery
• Most expensive fracture to treat on per-person basis
• ~25-30% at one year (higher than vertebral compression fractures)
• pre-injury mobility is the most significant determinant for post-operative survival
• in patients with chronic renal failure, rates of mortality at 2 years postoperatively, are close to 45%
• mortality risk is decreased at 30 days and at 1 year post-op when surgical intervention is performed within 24 hours of admission

Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC.

• - Femoral Neck Fractures

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Article Contents

Introduction, materials and methods, acknowledgements.

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Pathological progress of traumatic femur head necrosis after femoral neck fracture in children and adolescents: a case series study

Fan Yang and Zhikun Zhuang contributed equally to this work.

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• Supplementary Data

Fan Yang, Zhikun Zhuang, Yonggang Tu, Zhinan Hong, Fengxiang Pang, Wei He, Qiushi Wei, Ziqi Li, Pathological progress of traumatic femur head necrosis after femoral neck fracture in children and adolescents: a case series study, Journal of Hip Preservation Surgery , Volume 7, Issue 4, December 2020, Pages 696–704, https://doi.org/10.1093/jhps/hnab025

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The pathological progression and prognosis of traumatic femur head necrosis (TFHN) after femoral neck fracture (FNF) in children and adolescent is relatively unknown and has never been specifically characterized. As we speculated, the prognosis in such population would be poor and characterized as the high risk of femoral head collapse, hip deformity and degeneration in a short term. This retrospective case series enrolled 64 children and adolescent with TFHN who treated with observational treatment from 2000.1 to 2018.1. The primary outcomes, the progression of femoral head collapse, hip deformity (Stulberg classification) and hip degeneration (Tönnis grade), and their prognostic factors were analysed. Sixty-four patients with a mean age of 13 years (6–16 years) were included. A total of 28 hips (44%) showed unsatisfactory outcome and 25 (39%) hips collapsed progressively during a mean follow-up of 48 months (24–203 months). Finally, 38 hips (59%) experienced hip deformity, 20 of them were Class IV/V. Thirty-four hips (53%) generally progressed to osteoarthritis, 14 of them were classified as Grades II/III. The location of the lesion and the presence of subluxation were found to be related to progression of collapse; however, the presence of subluxation was the only independent risk factor of severe hip deformity and degeneration. TFHN in children and adolescent is a rapidly progressing disease with a poor prognosis characterized by a high risk of femoral head collapse progression. If the subluxation emerged, collapsed cases showed increasingly tendency towards hip deformity and degeneration.

Traumatic femur head necrosis (TFHN) is a potentially disabling complication that occurs after femoral neck fracture (FNF) in children and adolescent [ 1 , 2 ]. As TFHN is the most common complication, a meta-analysis revealed an average incidence of 23.5% [ 3 ]. And, another retrospective study, as the largest known sample size for paediatric FNF, indicated an incidence of 24.5% for TFHN [ 4 ]. However, this condition remains unfamiliar to most orthopaedic surgeons because of the rare incidence of primary injury [ 5 , 6 ]. Numerous studies have attempted to elucidate the incidence of TFHN and the relevant risk factors, but few have provided the characteristics of the pathologic progression, prognosis or the targeted treatment. Mirrored to the experience of adult FHN, or other childhood osteonecrosis caused by other aetiologies, hip-preserving operations, such as core decompression [ 7 , 8 ], free vascularized-fibular grafting [ 9 ] and hip osteotomy [ 10 ], have been used without confirmed evidence. In the absence of clear guidance, surgeons failed to make timely treatment plan, and observational treatment, such as non-weight bearing exercises [ 5 , 11 ] or pharmacotherapy [ 12 ], were used reluctantly.

As we have observed in clinical practice, TFHN rarely has a promising prognosis in children and adolescent. These patients were seemingly present with a strong tendency for femoral head collapse, a crucial pathologic change leading to poor outcomes, and hip deformity that occurs with skeletal maturity, which indicates a high risk of hip degeneration in immature patients [ 13 ]. We believe that these indicators, including femoral head collapse, hip deformity and degeneration, are the basis of the disease progression of TFHN in children and adolescent if they have not received proper treatment, but that have not yet been described in detail.

To the best of our knowledge, the largest sample size to date of 64 patients was included in the current study. We aimed to analyse the disease progression of TFHN in children and adolescent with a hypothesis that the prognosis in this paediatric population would be poor because of the high risk of femoral head collapse, hip deformity and osteoarthritic change.

This study was a retrospective case series study and was reported according to the STROBE statement [ 14 ]. After the approval of the Institute Ethics Committee (NO. ZYYECK[2020]053), a retrospective case study was conducted based on patients with TFHN in children and adolescent in our institute from 2000-1 to 2018-1, according to the following inclusion criteria: (i) participants diagnosed with TFHN [ 1 , 15 ] as a complication of a previous femoral neck fracture; (ii) patients with no history of corticosteroid administration or alcohol abuse; (iii) Epiphyseal plate of femoral head were not closed completely when the fracture occurred; (iv) patients with no other complications from FNF, such as nonunion or infection; (v) patients who completed a follow-up period of more than 2 years; and (vi) patients who had not received hip-preserving surgery after diagnosis (patients received surgery have already appeared severe femoral head deformity or osteoarthritis changes).

The treatment of included patients consisted of pain relief, restricted weight bearing and physical treatment, within the first 2 years after diagnosis of TFHN. We did not use any type of anti-osteoporosis medication because of the unknown complications in children and adolescents. Symptomatic treatments consisted of non-steroidal anti-inflammatory drugs (NSAIDs) or analgesics, as needed. The clinical and radiographic data were assessed at time of TFHN diagnosed and serially every 3–4 months within the first 2 years after treatment and every 6 months in the third year and subsequently.

Unsatisfactory outcomes were characterized by the conversion to THA or the presence of a ‘fair or poor result’ according to Ratliff’s clinical criteria [ 1 ]. Good was defined as ‘clinical, no or negligible pain; full or minimal restrictive hip movement; and normal or mild restricted activity’. Fair was defined as ‘clinical occasional pain; hip movement restriction <50%; and normal or mild restricted activity’. Poor was defined as ‘clinical or disabling pain; hip movement restriction >50%; and restricted activity’.

Radiographic data were collected, including X-ray, CT and MRI data. According to the classification system of the Japanese Investigation Committee (JIC) [ 16 ], all hips were classified into four types. Types A, B and C1 were assigned to groups where the necrotic area did not extend to the acetabular edge (inside coverage). Type C2 was assigned to groups where the necrotic area expanded beyond the acetabular edge (outside coverage). Then, we analysed whether the location of the necrotic area affected the prognosis. The degree of collapse was also evaluated by concentric circles on both anteroposterior and lateral radiographs referring to previous literatures [ 17 , 18 ]. With the increasing progression of femoral head collapse, subluxation was defined when Shenton’s line was not continuous, and the inadequate acetabular coverage was measured using the lateral center-edge angle (CE angle). The cases with CE angle <25° indicate inadequate coverage of the femoral head [ 19 , 20 ]. All radiographic quantitative evaluations were performed using ImageJ (1.52a, National Institutes of Health, Bethesda, MD, USA).

Three primary outcomes were evaluated as follows: (i) the progression of femoral head collapse more than 2 mm, (ii) the Stulberg classification and (iii) the Tönnis grade. The Stulberg classification [ 13 ] was used to describe the shape of the femoral head at skeletal maturity and to predict the long-term outcome at the last follow-up. The degree of osteoarthritis was defined according to the Tönnis grade (Grade 0–3) [ 21 ]. The Stulberg type IV/V was defined as severe hip deformity and Tönnis grade 2/3 was defined as degeneration change. All the hips in all patients at the last follow-up demonstrated skeletal maturity. All the radiographic characteristics and outcomes were evaluated by two experienced orthopaedic surgeons simultaneously and the consensus was discussed with another third surgeon.

Statistical analyses were carried out to analyse which factors, such as age, the location of the lesion and the presence of subluxation, would affect the primary outcomes. Then, adjusted-ORs were analysed by binary logistic regression. Cox proportional hazard model was used to identify the adjusted-HRs of predictive factors related to femoral head collapse progression. With an endpoint of the ‘progression of femoral head collapse’ according to X-ray images, a Kaplan–Meier analysis was performed, and survival curves were created with the log-rank test. A value of P  < 0.05 was considered to indicate significance. These statistical analyses were performed using SPSS Statistics (version 25; IBM, New York, NY, USA).

A total of 155 children and adolescents (155 hips) were diagnosed with TFHN from 2000-1 to 2018-1. After screening, 115 patients (115 hips) have complete medical record and radiograph data; 35 patients (35 hips) treated with surgery were excluded; and 16 patients lost to follow up in 2 years after the diagnosis of TFHN because of some personal reasons as they chose another hospital or lost contact. Sixty-four patients were finally analysed in our studies ( Fig. 1 ). The basic information of patients was shown in Table I . The mean follow-up time was 48.38 months (24–203 months). When patients were diagnosed, 14.1% (9/64) of hips exhibited subluxation and 10.9% (7/64) exhibited inadequate coverage of the femoral head on imaging. Then, 29.7% (19/64) of hips had subluxation after an average of 33.6 months (24–69 months). At the last follow-up, according to Ratliff’s clinical criteria, 36, 17 and 11 patients showed good, fair and poor outcomes, respectively. Five patients with poor clinical outcomes underwent total hip arthroplasty.

The flow chart of TFHN after FNF in children and adolescent underwent observational treatments.

The characteristics of TFHN and unadjusted analysis of factors related to primary outcomes

Abbreviations: FNF, femur neck fracture; JIC, Japanese Investigation Committee; TFHN, traumatic femur head necrosis.

Cox multivariate regression analysis.

Binary logistic regression.

Upon TFHN diagnosis, 48.4% (31/64) of hips had collapsed. Throughout the follow-up time, 39.1% (25/64) of hips progressively collapsed by more than 2 mm. And 54.8% (17/31) of the collapsed hips demonstrated collapse progression during follow-up. In addition, 70.3% (45/64) of hips ultimately progressed to the collapsed stage. If we defined collapse progression with an endpoint of more than 2 mm at follow-up, three factors consisted of the appearance of symptoms, JIC classification and subluxation, affected all primary outcomes through univariate analysis. The initial femoral head collapse related to the collapse progression and severe hip deformity ( Table I ). Furthermore, multivariate analysis indicated that the JIC classification (adjusted-HR = 6.127 95% CI = 1.8–20.9) and the presence of subluxation (adjusted-HR = 5.338, 95% CI = 1.6–17.8) were prognostic factors for the progression of femoral head collapse ( Table II ). The Kaplan–Meier curve showed the cumulative percentage of the progression of femoral head collapse and demonstrated a significant relationship between survival time and these prognostic factors ( Fig. 2 ).

The Kaplan–Meier curve showed the cumulative percentage of the progression of femoral head collapse ( a ) and demonstrated a significant relationship between survival time and prognostic factors ( b , c ). With the endpoint of ‘femoral head collapse progressing more than 2 mm’, the overall survival rates were 100.0, 83.3 and 22.2% in the JIC classification A/B, C1 and C2 respectively (b); the overall survival rates were 15.6 and 94.7% in those with and without subluxation of hip during follow-up (c).

Adjusted analysis of prognostic factors related to primary outcomes of TFHN in children and adolescent

Abbreviations: JIC, Japanese Investigation Committee; TFHN, traumatic femur head necrosis.

At the latest follow-up time, 59.4% (38/64) of the patients experienced hip deformity, indicating a devastating result for children and adolescents because of their high demand for hip function for their work and daily life. Specifically, 26 (40.6%), 18 (28.1%) and 20 (31.3%) patients were classified as having Class I/II, III and IV/V hips, respectively, according to the Stulberg classification. In univariate analysis, the type of symptom, JIC classification, initial femoral head collapse and subluxation were four factors related to severe deformity ( Table I ). However, multivariate analysis indicated that subluxation (adjusted-OR = 25.82 95% CI = 2.1–323.1) was the only indicator of severe hip deformity ( Table II ).

In terms of the Tönnis grade, 53.1% (34/64) of hips generally progressed to osteoarthritis. Twenty (27.8%) hips were classified as Grade I, 10 (13.9%) and 4 (5.6%) hips were classified as Grades II and III, respectively. In univariate analysis, the type of symptom, JIC classification, initial degree of femoral head collapse and subluxation were four factors that affected the results ( P < 0.05; Table I ). However, multivariate analysis indicated that subluxation of the hip (adjusted-OR = 13.46, 95% CI = 1.2–146.6) was the only indicator of severe hip degeneration.

A series of studies, first reported by Ratliff and his colleagues in the 1960s, have portrayed TFHN as a severe complication secondary to paediatric FNF [ 1 , 2 ]. Since then, the unsatisfactory outcomes of this condition have been repeatedly reported by numerous studies; however, the specific pathologic progression, prognosis and relevant risk factors for TFHN in children and adolescent remain unknown. This study is the first to address these deficiencies through a retrospective study that included 64 conservatively treated cases, which is thought to be the largest currently utilized sample size. The pathologic progression and prognosis of TFHN in children and adolescent were characterized in detail by femoral head collapse, hip deformity and hip degeneration. The most important finding in the recent study is that TFHN in children and adolescent is a rapidly progressing disease characterized by a high risk of femoral head collapse, deformity and osteoarthritis change. The subluxation of hip was considered to be the most significant risk factor to the poor prognosis of TFHN.

Femur head necrosis in the paediatric population can be induced by both non-traumatic and traumatic aetiologies. The non-traumatic aetiologies include corticosteroid-associated osteonecrosis, Legg–Calve–Perthes disease and the like [ 22 ]. Unlike non-traumatic cases, TFHN are far less common due to the rare incidence of FNF in children and adolescents. Thus, therapists might remain unfamiliar with TFHN because of the lack of guidelines and consensus documents. According to our study, a distinct difference exists in the pathologic progression and prognosis between TFHN and other non-traumatic cases of osteonecrosis.

The most intuitive characteristic of TFHN in children and adolescents was the high incidence of femoral head collapse progression, which is generally considered a turning point indicating poor prognosis in the short term [ 15 ]. The presence of collapse primarily depended on the lesion size and the location of the necrotic area, as the large involvement of necrotic lesions results in a high risk of femoral head collapse [ 15 , 16 ]. We believe that patients with TFHN were susceptible to extensive necrosis due to severe damage of blood supply induced by high-energy primary trauma. Ratliff and his team demonstrated the highest incidence of TFHN occupying the total head (Type I), followed by partial necrosis of the epiphysis (type II) and necrosis between the epiphyseal plate and the fracture line (Type III) [ 1 ]. A high risk of total head necrosis, ranging from 35.7% to 80.7% [ 1 , 5 , 23–26 ], has been confirmed repeatedly by studies on the same subject. The high risk of large lesions and disease progression does not seem to be common in corticosteroid-associated children and adolescents.

Legg–Calve–Perthes disease is also a common aetiology of childhood osteonecrosis, usually with extensive and severe involvement of the epiphysis. Canavese et al . described the prognosis of Legg–Calve–Perthes disease in patients under 6 years old [ 27 ]. According to the Catterall classification, 50 hips had mild involvement (Grade I/II), and 116 hips had severe involvement (Grade III/IV). Similarly, 358 patients with Legg–Calve–Perthes disease (mean age, 5.8 years) were followed for more than 5 years with radiographic data by Wiig et al . and 87.7% (314/358) of whom exhibited severe involvement (Grade III/IV) [ 28 ].

However, these severely involved patients with Legg–Calve–Perthes disease had a better prognosis than TFHN. First, TFHN tended to be associated with severe deformity. The percentages of Stulberg class III and IV/V hips in our study were 28.1% (18/64) and 31.3% (20/64) in patients with TFHN. The matched data for patients with Legg–Calve–Perthes disease were 22.4% (26/116) and 10.3% (12/116) in the study of Canavese et al . [ 27 ] and 36.6% (115/314) and 19.2% (60/314) in the study of Wiig et al . [ 28 ]. Second, during our follow-up of children and adolescent with TFHN, hip degeneration progressed rapidly, which was obviously different from patients with Legg–Calve–Perthes disease, which hardly experienced any osteoarthritic changes in the short term until their 40 s and 50 s [ 13 ].

In general, TFHN seemed to be more susceptible to hip deformity and degeneration compared with Legg–Calve–Perthes disease in paediatric population. As we speculated, the weakened abilities of bone repair and remodelling with older age were other potential causes of poor prognosis in patients with TFHN. The average age of the included patients in our study was nearly 13 years old. In this age group, patients with bone necrosis lack satisfactory repair and remodelling abilities and show completely different prognosis and pathological processes than younger patients [ 29 , 30 ]. Spontaneous femoral head repair and remodelling into a spherical shape were never observed in our patients at the collapsed stage. Even with the largest sample size of such condition, the samples still did not report the results for all ages of children and adolescents. For instance, we only included a small proportion of children younger than 11 years of age (six cases), who would presumably have a better prognosis.

Hip incongruency and instability secondary to irreversible deformity were the major causes of rapid cartilage damage. According to our multivariate analysis, as subluxation occurred during the follow-up, the risk increased sharply by 26-fold for severe hip deformity and 13-fold for severe hip degeneration ( Table II ). Osteoarthritic changes represented the primary cause of arthroplasty in our patients. Our work determined that the pathologic progression and prognosis of TFHN in children and adolescent was specific and different from corticosteroid-associated osteonecrosis or Perthes disease.

As a sign of a ‘head at risk’, subluxation of the hip was defined as the strongest independent risk factor for primary outcomes in our results. For immature patients, subluxation signifies instability of the hip joint. The former is a widely recognized adverse effect of femoral head remodelling, and the latter increasingly exacerbates hip degeneration. Other recognized prognostic factors of progression of femoral head collapse for most types of osteonecrosis of femoral head, such as the initial degree of femoral head collapse [ 31 ], JIC classification [ 16 ] and symptoms [ 32 ], show no apparent relation to severe hip deformity and degeneration. Therefore, these factors did have value for predicting femoral head collapse, but after collapse, not all hip showed further progression to severe hip deformity and degeneration. If the subluxation emerged, cases at collapsed stage showed increasingly tendency towards severe hip deformity and degeneration in short term ( Fig. 3 ), otherwise they might keep satisfactory hip condition ( Fig. 4 ).

Adolescent of TFHN at collapsed stage showed an increasingly progression towards severe hip deformity and degeneration in the short term, if the subluxation emerged. A male patient of 16 years old, with left FNF, treated with three cannulated screws ( a ). TFHN (JIC classification C2) was diagnosed 1 year after FNF, which already progressed to collapsed stage with subluxation ( b ). During observational treatment, radiographs showed progressively femoral head collapse and subluxation 11 months after diagnosis of avascular necrosis ( c ). At latest follow-up, 2 years after FNF, left hip showed poor outcome according to Ratliff’s clinical criteria, with severe hip deformity (Stulberg classification IV) and hip degeneration (Tönnis grade III).

Children with TFHN at collapsed stage showed a satisfactory outcome in a long-term follow-up when their hips were in a stable condition (without subluxation). A male patient of 14 years old, with right FNF, treated with Kirschner wires. TFHN (JIC classification C2) was diagnosed 1 year after FNF ( a ). During observational treatment, radiographs showed progression of femoral head collapse after 1 year follow up, but still without subluxation ( b ). At 2 years follow-up, it still showed no significant progression of collapse and deformity ( c ). After 5 years, the patient still got good outcome according to Ratliff’s clinical criteria, with mild hip deformity (Stulberg classification II) and mild hip degeneration (Tönnis grade I).

However, several limitations still exist. First, the hospitalized patients included in current study have potential risk of selective bias. However, due to the rareness of this kind of disease, the data collection and follow-up of outpatients have much difficulty. Second, we set up a minimum follow-up of 2 years, and finally presented a middle-term result of 4 years on average. To be sure, it was not a long enough period to describe the complete course for most hip problems in paediatric population. However, under the limited follow-up, our results provided a cautionary and useful note of TFHN in children and adolescent, ‘rapid deterioration and relevant factors’, that would be beneficial for clinical decision. Further prospective multi-centre control trials with more cases or control groups are suggested to confirm the results. At last, due to the lack of radiograph data when the fracture happened, we did not analyse the correlations between the prognosis of TFHN and other factors such as initial displacement of the fracture, Delbet classification, time to treatment and residual displacement. And, it would be further studied in future.

In summary, our recent study first identified the characterization of the prognosis of TFHN in child and adolescent. Over half of our patients had hip involvement with osteoarthritic changes or femoral head deformities. Therefore, we believe that TFHN in children and adolescent is a rapidly progressing disease with a prognosis characterized by a high risk of femoral head collapse. For patients who also have hip subluxation, a sign of ‘head at risk’, severe hip deformity and degeneration will occur and result in poor outcomes in the short term. For such conditions, the ideal treatment should be targeted at decreasing the risk of femoral head collapse and rectifying the hip instability induced by subluxation at the same time.

The authors thank Pengfei Xin (Guangzhou University of Chinese Medicine, Guangzhou, China) for helpful assistance on the data extraction and Masatoshi Oba (Yokohama City University, Yokohama, Japan) for the help of statistical verification.

National Natural Science Foundation of China (81904226, 81873327).

CONFLICT OF INTEREST STATEMENT

The authors have no conflicts of interest relevant to this article.

DATA AVAILABILITY STATEMENT

The full original data of the article is available in the official website of Oxford academic.

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Author notes

• femoral neck fractures
• femoral head
• femur head necrosis
• osteoarthritis
• prognostic factors
• tissue degeneration
• primary outcome measure

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Management of an isolated neck-of-femur fracture in an elderly patient

Georgette Eaton

South Central Ambulance Service

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Femoral neck fractures affect up to 75 000 elderly people per year, with up to a third of these patients dying within twelve months. While there is a paucity of research specific to the pre-hospital field, current evidence demonstrates that optimal treatments include appropriate and adequate analgesia, fluid management and correct immobilisation of the injured leg. Analgesia should be considered in a step-wise approach and should be progressive to the patients' needs.

Pain relief should be sought through the variety of options open to paramedics and should be initiated immediately. Transfer to the ambulance should be done in a safe manner, ensuring the patient is immobilised and remains pain free. This pre-hospital management of the patient with a femoral neck fracture ensures they receive adequate analgesia and fluid replacement before any definitive treatment at hospital.

Femoral neck fractures are one of the most common limb injuries encountered in the pre-hospital setting and affect up to 75 000 elderly people each year ( British Orthopaedic Association, 2007 ). Despite being a common injury, it should not be underestimated; 10% of people with these fractures die within 1 month and up to a third within 12 months ( National Clinical Guideline Centre, 2010 ).

While the majority of these deaths are attributed to co-morbidities (such as pneumonia), effective management from the start of the injury is likely to reduce mortality. A key component of this management surrounds the pharmacological interventions paramedics can offer, particularly to combat pain and prepare the patient for surgery. This article focuses upon pain management in the pre-hospital setting, specifically related to management of femoral neck fracture. The need for a competent assessment of this injury (including a pain assessment) is recognised but is beyond the remit of this article.

What is a femoral neck fracture?

The femoral head and neck lie within the joint capsule of the hip joint, and the head of the femur moves within the acetabulum. The most common site of fracture is within the intracapsular region, largely as a result of the periosteum being very thin and increasingly diminished around the femur ( Dolan and Holt, 2008 ).

Garden’s (1964) classification of femoral neck fractures is still widely used by physicians and describes four stages of fracture; Stage I represents impacted fractures, Stage II demonstrates non displaced fractures, Stage III depicts displaced fractures and Stage IV portrays displaced and adducted fractures ( Figure 2 ). While these different types of fractures may seem to have little implication for emergency assessment and management, it is important for the pre-hospital clinician to understand that there are differing types of femoral neck fractures to ensure that a full patient assessment is carried out ( Dolan and Holt, 2008 ). While shortening and rotation are often the cardinal signs of femoral neck fractures, it is only prevalent with a stage IV fracture, so the absence of this sign does not eliminate the risk of a fracture to the femoral neck. The other three types of fracture are unlikely to present with these cardinal signs, even though a fracture to the femoral head has occurred. For this reason, a full assessment should be carried out on any patient with a suspected fracture to the femoral neck.

Why do they occur?

The majority of femoral neck fractures occur in female patients aged over 80 years ( Parker and Johansen, 2006 ). The usual mechanism of injury is minor or indirect trauma, although many other factors contribute to the problem (Eiff et al, 1998). These factors include the increased tendency for elderly people to fall, reduced bone strength and osteoporosis (particularly in women), and a loss of protective reflexes when falling—meaning falls tend to be on the hip and thus the already weak femoral neck becomes fractured ( Parker and Johansen, 2006 ).

Pre-hospital assessment

All pre-hospital assessments should follow the systematic ABCDE approach to eliminate life threatening presentations. In suspected femoral neck fractures it is important to ascertain the underlying reasons for the fall: whether it is mechanical (due to stumbling) or medical. It is for this reason that a cardiac and metabolic assessment should take place to include blood pressure, a 12 lead electrocardiogram and a blood glucose reading ( Greaves and Porter, 2010 ).

A formal assessment of pain status should also be carried out in order to facilitate appropriate patient management ( Gloth, 2004 ). This should include a thorough assessment of the pain and include one of three common pain rating scales: the visual analogue scale or the verbal rating scale or the numerical rating scale. Williamson and Hoggart (2005) outline that the numerical rating scale often provides the most sensitive data, but patients’ often prefer a verbal rating scale—though this can be misunderstood. With this in mind, a combination of these scales may be appropriate, particularly considering the various co-morbidities of the elderly (including deafness or dementia).

Examination for musculoskeletal injuries should follow the ‘look, feel and move’ principles of assessment, although this is unnecessary in the presence of obvious fractures and should be ceased if it will produce further pain ( Greaves and Porter, 2010 ). In the ‘move’ element of this assessment, the clinician should assess whether the patient can perform a straight leg raise (hip flexion) and flex the knee. Except for minor (incomplete) fractures, patients with any fracture to this region will be unable to perform a straight leg raise ( Greaves and Porter, 2010 ). However, it should be remembered that patients with generally poor mobility or osteoarthritis may also have difficulty in moving their leg in this manner. By questioning the patient about any new pain or a new reduction in their mobility, the indication of a new fracture may be sought.

Hydration status should also be assessed in the pre-hospital environment. This can be done by testing the turgor of the skin by gently squeezing the skin on the patient’s forearm and observing for the length of time it takes to return to its original shape—more than 30 seconds is considered to show dehydration ( Buss, 2011 ). Dehydration is believed to contribute heavily to mortality rates following hospital treatment, which will be discussed further ( McRae and Esser, 2002 ; Sutcliffe 2006 ; Dolan and Holt, 2008 ).

Clinical symptoms and signs

As there are four types of femoral neck fracture, not all fractures will show shortening and rotation, and more atypical presentations do exist. There are certain signs that are characteristic of fractures to this site. In the first instance, patients will often be lying in the position that they fell, unable to move due to pain, which may be in the groin and through the thigh to the knee. Except for minor (incomplete) fractures, patients with any fracture to this region will be unable to perform a straight leg raise ( Greaves and Porter, 2010 ).

In stage IV fractures, the leg may appear to be externally rotated and slightly adducted as displacement has occurred at the fracture site. With all types of this fracture, pain is often worsened on movement and patients are usually unable to bear weight following the injury ( Crawford-Adams and Hamblen, 1999 ; Gates and Mooar, 1999 ; Greaves and Porter, 2010 ). Clinicians should remember that there are a range of pain experiences; although a fracture to the femoral head is regarded as a painful condition, some patients may not complain of pain at all. Therefore, any suspected fracture should be fully exposed and evaluated, and clinicians should not rely on looking for deformity or areas of pain alone ( Vassiliadis, 2002 ).

Pre-hospital management–pain relief

Pain relief is regarded as an ethical human right, set out by The International Covenant on Economic, Social and Cultural Rights ( The Office of the United Nations High Commissioner for Human Rights, 1966 ). This pronounces the right ‘of everyone to the enjoyment of the highest attainable standard of physical and mental health’.

Thus, there is a strong argument for an individual’s right to pain relief from the expressed right to health. Untreated pain can not only produce psychological stress and anxiety, but also produces a neuro-humoral response ( Dunwoody et al, 2008 ). This increases the sympathetic response, resulting in increased tachycardia, elevated blood pressure and increased oxygen consumption ( Liu and Gropper, 2003 ), and poor wound healing ( Kopf and Patel, 2010 ). For both ethical and physiological reasons, paramedics should seek to give pain relief to any patient complaining of pain.

To provide optimal pain relief, a comprehensive pain assessment is essential, but should also be continual to ensure that the appropriate treatment is given and an adequate response maintained ( Herr, 2011 ). Many patients with femoral neck fractures do not receive pre-hospital analgesia, despite complaining of pain, and further analgesia administration in the emergency department is influenced by whether the patient has been given pre-hospital pain relief ( Kelly, 2000 ; Vassiliadis et al, 2002 ). While a conventional ladder pain assessment may be difficult to obtain in elderly patients (due to dementia or other chronic painful conditions), a combination of pain scales and a thorough history of the injury from the patient (and family where necessary) can help identify and locate any pain, which can then be treated accordingly ( Williamson and Hoggart, 2005 ; Gregory and Ward, 2010 ). Fisher, Brown and Cooke (2006) advocate that suitable analgesia should be given to patients with femoral neck fractures.

In the United Kingdom, under the Joint Royal Colleges Ambulance Liaison Committee (JRCALC), paramedics are approved to administer four types of analgesics: inhalational analgesia (nitrous oxide/oxygen mix), oral analgesia (paracetamol and ibuprofen), parenteral and enteral analgesia (morphine) and topical analgesia (tetracaine, lignocaine). Individual ambulance trusts may also use patient group directives (PGDs) to provide their clinicians with a greater range of analgesic options, such as codeine, tramadol and IV (IV) paracetamol.

Entonox is recommended for patients with lower extremity fractures ( Lee and Porter, 2005 ; Thomas and Shewakramani, 2008 ). Entonox has a very low solubility in blood, which allows for rapid saturation in the brain (where it has its anaesthetic effect) and also rapid elimination; hence it does not mask any signs or symptoms that may aid a differential diagnosis ( Simonsen et al, 2006 ). The adverse effects of entonox (including dizziness) are deemed to be outweighed by the benefits of immediate pain relief. As good pain relief from entonox is consistent across a diverse group of investigations, reliability in the combined results reinforces the applicability of this drug for musculoskeletal injuries ( Faddy and Garlick, 2005 ; Lindsay, 2007 ).

While it is useful to treat a diverse group of injuries, there are potential problems related to the method of administration, especially in elderly patients. The device used to deliver entonox works on a demand valve activated by the patient’s inspired breath, however, there must be a minimum effort of 0.25 kPa ( British Oxygen Company, 2010 ).

Peak inspiratory pressures tend to decrease due to decreased respiratory muscle force, as part of the ageing process ( Tack et al, 1983 ). With this in mind, some elderly people who sustain femoral neck fractures may not have respiratory muscles strong enough to create the required pressure to activate the demand valve and obtain the drug. In addition, the device may need to be altered to provide optimal drug uptake. Gregory and Mursell (2010) advocate the use of a face mask rather than mouth piece for administration of this analgesic, as the face mask allows full inhalation of the drug and minimal outside air. However, it should be recognised that, as entonox should only be self administered by the patient ( Fisher et al, 2006 ), some elderly patients may have difficulty in holding the face mask to their face in an appropriate manner. For this reason, this analgesic may not be appropriate for all elderly patients and continuous assessments need to be done by the clinician to evaluate its effectiveness.

Lee and Porter (2005) advocate the use of entonox for splinting and transfer-manoeuvres, which would take place in the pre-hospital environment. In patients who are able to activate the demand valve and are able to self administer the drug, it should be administered via a face mask to provide initial pain relief while other drug treatments are being prepared. Following the transfer of the patient to the ambulance stretcher, it is more appropriate to consider other avenues of pain relief, as the use of entonox in the elderly group can be poor and, therefore, the analgesia being provided is suboptimal.

Ibuprofen and paracetamol

Oral analgesia in the form of paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs) are not considered immediate analgesia in the treatment of lower leg injuries; trauma injuries or specific femoral neck injuries ( Vassiliadis, 2002 ; Lee and Porter, 2005 ; Thomas and Shewakramani, 2008 ), though they may still provide effective pain relief. A search of key medical databases (Pubmed and Cinahl, 2012) revealed a paucity of recent research on this topic, possibly on ethical grounds. Both ibuprofen and paracetamol are thought to reduce pain by inhibiting the synthesis of prostaglandins, though the complete mechanism of action is not fully understood. Ibuprofen inhibits cyclooxygenase (the agent that catalyses the manufacture of prostaglandins) and also limits the inflammatory response, as well as acting on peripheral nociceptors—reducing the generation of nociceptive (pain) impulses ( Simonsen et al, 2006 ).

By inhibiting the production of prostaglandins, acid secretion in the stomach increases as prostaglandins prevent the synthesis of hydrochloric acid in the stomach mucosa. This results in acid-related inflammation of the stomach and sometimes bleeding, which can have a profound effect on the elderly patient if taken regularly.

‘The IV route offers an almost immediate onset of effect and can be titrated to clinical effect’

side effects (including gastrointestinal disturbance and fuid retention) in the elderly population. For this reason, even a single dose of NSAIDs are not recommended as analgesia for patients with femoral neck fractures, and paracetamol should be used instead ( National Clinical Guideline Centre, 2010 ).

The mechanism of paracetamol is not fully understood so far, but it is thought to have a combination of a peripheral and central effect. The peripheral effect is COX-2 inhibition, which inhibits prostaglandin synthesis and has a peripheral effect on the nociceptors in a similar way to ibuprofen ( Simonsen et al, 2006 ). Recent studies suggest it is also has a central effect that first reinforces the activity of endogenous opioid and/or cannabinoid systems in the brain. From here it is also thought to reinforce the effect on the descending serotonergic pathways and spinal 5-HT7 receptors to reduce sensitivity to pain stimuli (Dogrul et al, 2012). The National Clinical Guideline Centre (2010) advocates paracetamol as a safe drug to use, largely due to the diminished risk of gastrointestinal bleeding. Therefore, paracetamol is deemed an effective analgesic and can be used either singularly or alongside other analgesia in the pre-hospital management of femoral neck fractures. However, one major limitation of giving repeated doses of oral paracetamol is the limit in its analgesic efficacy—once the maximum dose has been given, and the patient is still complaining of pain, further doses will have no further effect and a toxic level may be reached once the patient is in hospital ( Hawthorn and Redmond, 1999 ; Parsons and Preece, 2010 ). For this reason, a combination of analgesia may be required.

Some ambulance trusts use PGDs to maximise the pain relief available for their patients. Two common PGDs are for oral codeine phosphate and tramadol, both weak opioids. Tramadol has long been used to treat musculoskeletal pain and there is evidence to show that it has a strong analgesic efficacy after the initial dose ( Pagliara et al, 1997 ), but is often only available to ambulance nurses or emergency care practitioners. Codeine phosphate is also shown to be effective for the treatment of musculoskeletal pain, but the elderly patient is more likely to experience adverse effects, such as dizziness, vomiting or constipation, than with tramadol ( Gloth, 2004 ). It is worth noting that codeine is a ‘pro-drug’ converted to morphine inside the stomach in phase 1 metabolism (McGavock, 2010). Codeine reaches its maximum analgesic effect when administered alongside paracetamol and, for this reason, should be considered alongside paracetamol as the first course of treatment for any musculoskeletal injury ( Moore et al, 1997 ).

However, there are limitations in administering any oral analgesic to patients in severe pain. The time to optimal pain relief using the oral route is at least 20 minutes ( Simonsen et al, 2006 ) and patients in severe pain have a delayed gastric absorption rate ( Dunwoody et al, 2008 ), thus prolonging optimal analgesic effects. In addition, patients who have sustained this fracture are often lying on the foor, and will remain lying down for immobilisation and transfer, they may be unable to physically swallow a tablet. While this should not be a deterrent for administering oral analgesics, the patient’s severity of pain should be thoroughly assessed and more prompt pain relief may need to be considered.

The National Clinical Guideline Centre (2010) advocates offering opioids if paracetamol alone does not provide sufficient relief. Morphine works centrally in the midbrain nuclei and cerebral cortex. It stimulates the release of 5-HT noradrenalin and enkephalins, which directly inhibit the spinal dorsal horn and further inhibit the peripheral terminals of the pain fbres. In this way, it inhibits pain signals both centrally and peripherally.

There are three opioid receptors: μ (mu), δ (delta) and κ (kappa). Natural opioids (enkephalins) target all these receptors, but morphine and other opiate analgesics bind selectively to the mu receptor ( McGavock, 2010 ). IV (IV) morphine provides very effective analgesia, which can be titrated to clinical effect and patient need, rather than giving a single dose as with oral morphine ( Lee and Porter, 2005 ). IV morphine is the fastest working and longest lasting opioid when compared with intramuscular and oral morphine. The IV route offers an almost immediate onset of effect and can be titrated to clinical effect (rather than block administration with intramuscular (IM) and oral morphine); and has a duration of up to 4 hours ( Thomas and Shewakramani, 2008 ).

While it is believed that elderly patients are more susceptible to the adverse effects of opioid analgesics ( National Clinical Guideline Centre, 2010 ), lower doses of morphine at 0.05 mg/kg are inappropriate for treating severe pain, and higher doses starting at 0.1 mg/kg are found to be effective for use in the pre-hospital setting ( Bounes et al, 2008 ).

The average weight of an 80-year-old female (the age and sex where femoral neck fractures are most common) is approximately 60 kg. Therefore under this guidance, 6 mg of morphine should be the initial dose for severe pain in this age group. This is in contrast to current guidelines, which advocate only 2.5 mg for elderly patients over 65, possibly due to the potential side effects ( Fisher et al, 2006 ). Therefore, the paramedic needs to create a balance between these two doses: a dose not so low as to inadequately treat pain, but not so high that the potential side effects (including respiratory depression and nausea) outweigh the benefits.

It is this weight-dose link that presents the problem with the administration of intramuscular (IM) or oral morphine, as block administration may not treat the pain at all or intensify these side effects. The rate of absorption of IM morphine is dependent on muscle mass, tissue perfusion and dehydration ( McGavock, 2010 ). Oral morphine is again dependent on gastric motility, which is reduced in severe pain ( Dunwoody et al, 2008 ). However, since the analgesic efficacy of IM and oral morphine is arguably less than IV administration ( Thomas and Shewakramani, 2008 ), it could be argued that this block administration does not present a problem regarding adverse effects, but may not provide adequate pain relief. Problems regarding the patient lying down may mean oral morphine is contraindicated due to risk of choking ( Fisher, Brown and Cooke, 2006 ) or a loss of muscle mass in the elderly patient may make intramuscular injection more challenging. The pre-hospital clinician needs to use their autonomy to decide on the most appropriate route of morphine for each individual patient.

While morphine is currently the most widely available IV opioid that can be administered by paramedics ( Medicines and Healthcare Products Regulatory Agency, 2011 ), other opioids may be effective in reducing pain in the pre-hospital environment. In a comparison of intranasal fentanyl and IV morphine, there was no statistical difference in pain reduction from the baseline value to that obtained at hospital, demonstrating that these different opioids were not significantly different in their pre-hospital effectiveness ( Rickard et al, 2007 ). Similar results were found by Galinski et al (2005) comparing the IV routes of administration for fentanyl and morphine. Intranasal fentanyl was easier to administer due to the accessible intranasal route, and had a rapid effect due to the quick absorption rate. This is in contrast to the IV route, where some patients are unable to be cannulated and others refuse treatment due to needle phobia. However, fentanyl is a fat soluble opioid. This allows it to have a quick absorption rate, but also has a half life of 15 minutes. This is comparable to IV morphine, which has a slightly slower onset (being a water soluble opioid), but a half life of 200 minutes ( McGavock, 2010 ). With this in mind, the intranasal route would be ideal in a patient in whom IV access is difficult but fentanyl may not be the most suitable opioid in the treatment of a femoral neck fracture, where a longer lasting analgesic would be more appropriate.

‘Pain relief for femoral neck fractures should be considered in a step-wise approach’

As a final point, pain relief for femoral neck fractures should be considered in a step-wise approach. This should ideally start at entonox, progress towards oral paracetamol and additionally morphine. If PGDs to provide further pain relief, such as tramadol, codeine or IV paracetamol are active within the paramedics’ trust, these further analgesics should be incorporated into this step-wise approach. The paramedic should assess patient status and use their clinical judgement to determine the type and route of analgesic to ensure the patient remains pain free throughout ( The National Clinical Guideline Centre, 2010 ). Currently, IV morphine appears to be the best form of analgesia that can be given to elderly patients by all paramedics, providing it has an initial higher dose and is titrated to clinical effect ( Lee and Porter, 2005 ; Bounes et al, 2008 ; The National Clinical Guideline Centre, 2010 ).

Pre-hospital management–fluid rehydration

Dehydration is associated with increased mortality following femoral neck fracture and the use of IV crystalloids prior to surgery is advocated ( McRae and Esser, 2002 , Sutcliffe; 2006 ). The principle goal of fuid administration is to maintain tissue perfusion (through hydration status) and compensate for fluid loses during surgery ( Arkilic et al, 2003 ; Chong et al, 2009 ). Inadequate fluid resuscitation can lead to organ failure, due to decreased intravascular volume and inadequate interstitial perfusion—affecting cardiac, pulmonary, renal and gastrointestinal systems ( Chong et al, 2009 ). However, excessive fluid resuscitation may lead to cardiac failure, resulting in complications following surgery and poor survival rates ( Venn et al, 2002 ; Brandstrup et al, 2003 ). Nevertheless, fluid administration before and during surgery shortens the time to being medically fit for discharge and is an intervention that can be started in the pre-hospital setting ( Venn et al, 2002 ).

However, a majority of this research focuses on fluid administration before, during and following surgery, with a deficiency in pre-hospital evidence. Fisher, Brown and Cooke (2006) advocate both sodium chloride and sodium lactate with a loading volume of 250 ml to reverse dehydration and improve tissue perfusion. IV fluids are generally advocated for initial replacement in the pre-hospital arena if dehydration is detected or if there is a prolonged journey time to hospital or transfer to a hospital bed, as it is a basic resuscitative manoeuvre ( Bhangu et al, 2010 ; Greaves and Porter, 2010 ).

Pre-hospital management–immobilisation

The application of a splint is deemed essential in reducing pain. Principles of immobilisation include continual reassessment of the neurovascular status prior to and following the immobilisation of the joints above and below the fracture ( Lee and Porter, 2005 ). As the femoral neck is within the pelvis (and so cannot be easily splinted above the fracture site), the whole leg is immobilised to reduce movement and so prevent pain.

Following the administration of appropriate analgesia, the leg should be repositioned (if required) and secured to the uninjured leg ( Greaves and Porter, 2010 ). Figure 4 shows the appropriate way to splint a suspected femoral neck fracture. There should be padding between the legs, using either an ambulance service blanket or multiple triangular bandages. Broad bandages should be used above and below the knee, splinting the injured leg to the good leg. A figure of eight knot around the ankles will prevent further movement of the injured leg, helping to reduce further pain ( Lee and Porter, 2005 ).

Nevertheless, there are some limitations with this type of splinting. Although the injured leg is secured to the good leg, there is still a possibility of movement from the hips–causing further pain and possibly worsening the fracture, depending on severity. As this injury is often due to a fall (Eiff et al, 1998), these patients will also require lifting onto a stretcher and moving into the ambulance.

The use of carry or striker chairs to convey patients with these injuries should be avoided. Not only will movement (and so pain) be magnified during transfer, further injury to surrounding tissue may also occur due to impaction of the injury. A scoop stretcher is the most appropriate type of lifting aid, as it reduces the need to log roll the patient and so prevents any further movement which may cause damage (Krell et al, 2007). However, in practice, scoop stretchers can be difficult to use if patients need to be manoeuvred down stairs or where there are other space restrictions. In addition, lying down flat may aggravate other chronic conditions the patient may have (such as respiratory diffculties) and may initiate the development of pressure sores–which could be further exacerbated in hospital. While the scoop stretcher is deemed the best and safest method for removal of the patient, the clinician needs to weigh up each situation individually to ensure the most appropriate aid for removal is used to reduce pain, reduce impaction of the fracture and to promote tissue viability.

As fractures to the femoral neck are so common, there is a need for paramedics to be able to recognise both the cardinal signs and atypical features of these fractures and provide the highest level of care to reduce morbidity and mortality. Alongside this recognition should be investigations to discover the reason for the fracture, to reduce other co-morbidities ( Parker and Johansen, 2006 ; Greaves and Porter, 2010 ). Pain relief should be instigated early, ideally in a step-wise approach using entonox and oral paracetamol. However, bearing in mind the slow mechanism of onset for paracetamol, the paramedic should use their clinical judgement to assess the status of the patient and consider the immediate administration of IV morphine in conjunction with ambulance service guidelines ( Fisher et al, 2006 ; National Clinical Guideline Centre, 2010 ). Secondary to pain relief, hydration status should be assessed to prepare the patient for surgery ( McRae and Esser, 2002 ) and fluid replacement should be commenced if the patient appears dehydrated or if journey time to hospital is prolonged ( Greaves and Porter, 2010 ).

Immobilisation of the injured leg and transfering using the scoop stretcher not only reduces further pain but also provides a safe means of transferring the patient to the ambulance and prevents further damage to the leg ( Lee and Porter, 2005 ). This pre-hospital management of the patient with a femoral neck fracture ensures the patient will receive the highest levels of care in the scope of practice of a paramedic by providing adequate analgesia and fluid replacement before any definitive treatment at hospital.

• Open access
• Published: 14 September 2024

Comparative analysis of the femoral neck system (FNS) vs. cannulated cancellous screws (CCS) in the treatment of Middle-aged and elderly patients with femoral neck fractures: clinical outcomes and biomechanical insights

• Jun Sun 2 ,
• Junjie Li 3 ,
• Feng Huang 1 ,
• Jinxiang Zhao 4 ,
• Yiping Shao 4 ,
• Shuping Fang 4 ,
• Ziru Wang 5 ,
• Yu Gong 1 ,
• Hao Zhou 1 &
• Shoujin Tian 6  

BMC Musculoskeletal Disorders volume  25 , Article number:  735 ( 2024 ) Cite this article

Metrics details

This study aimed to compare the clinical outcomes and differences in biomechanical characteristics between the femoral neck system (FNS) and cannulated cancellous screws (CCSs) in the treatment of femoral neck fractures.

This study retrospectively analysed a cohort of 38 registered cases of femoral neck fractures treated surgically with either the FNS ( n  = 17) or CCSs ( n  = 21) between January 2020 and December 2023. Indicators such as fluoroscopy frequency, length of hospital stay, and fracture healing time were compared between the two groups. Functional status was evaluated via the Harris hip score (HHS) and visual analogue scale (VAS), whereas prognosis was assessed based on changes in the neck shaft angle and femoral neck shortening. Additionally, six sets of femoral neck fracture models were developed based on Pauwels angles of 30°, 40°, 50°, 60°, 70°, and 80°. Two experimental groups, FNS and CCS, were established, and a joint reaction force of 1800 N was applied to the proximal femur. The displacement, stress, and stiffness of the components of interest in the different models were tested and compared.

The distributions of all the baseline characteristics were similar between the two groups ( p  > 0.05). The FNS group presented significantly shorter fluoroscopy frequency, length of hospital stay, and fracture healing time ( p  < 0.05). Harris and VAS scores were higher in the FNS group than in the CCS group ( p  < 0.05). Postoperative changes in the neck shaft angle and femoral neck shortening were significantly lower in the FNS group than in the CCS group ( p  < 0.05). The results of the finite element analysis indicated that the maximum stress on the femoral head and varus angle were generally lower in the FNS group than in the CCS group and that the maximum displacement of the femoral head and FNS was generally lower in the FNS group than in the CCS group. However, the superiority of FNS over CCS decreased with increasing Pauwels angle. Additionally, the effectiveness of FNS in limiting displacement of the femoral neck upper wall was not as favourable as that of CCS.

Conclusions

The treatment of femoral neck fractures with FNS is superior and contributes to improved hip joint function. Biomechanical research has confirmed its structural stability and advantages in resisting femoral head varus. However, challenges to its fixation efficacy persist, particularly at higher Pauwels angles.

Peer Review reports

Introduction

Femoral neck fracture is a common orthopaedic condition that accounts for approximately 57% of hip fractures [ 1 ]. It often occurs in elderly individuals as a result of low-energy falls. With advances in medical technology, the treatment outcomes of femoral neck fractures have significantly improved [ 2 ]. However, elderly individuals with hip fractures still face many risks, including decreased quality of life, increased care demands, secondary osteoporosis, and mortality [ 3 ]. Once a fracture occurs, the mortality rate within one year can increase from 14 to 36% [ 4 ]. How to treat these femoral neck fracture patients quickly and effectively is a problem that clinical doctors must address.

There are various methods of internal fixation for femoral neck fractures, with commonly used options including dynamic hip screws (DHSs) and multiple cannulated screws. Currently, the most widely used method is fixation with three cannulated cancellous screws (CCSs). However, there is no correlation among the three screws, and their positioning is susceptible to subjective and objective factors related to the surgeon. As a result, their resistance to vertical shear and torsion is relatively poor, which may lead to loosening and displacement of the fracture ends, avascular necrosis and nonunion of the femoral head, and shortening of the femoral neck [ 5 ]. There is still an early complication rate of 10–30%, including nonunion and internal fixation failure [ 6 ].

According to Pauwels, femoral neck fractures are classified into three types based on the the angle between the fracture line in the coronal plane and the superior margin of the acetabulum: Pauwels type I when the angle is less than 30°, type II when it ranges between 30° and 50°, and type III when the angle exceeds 50°. The greater the Pauwels angle is, the closer the fracture line is to the vertical direction, leading to increased shear forces at the fracture site and greater instability, which are often associated with a greater incidence of fixation failure and nonunion [ 7 ]. Studies report nonunion rates of 16–59% and avascular necrosis rates of 11–86% for unstable Pauwels type III femoral neck fractures [ 8 ]. The femoral neck system (FNS) was developed in 2017 by Stoffel et al. [ 9 ]. Combining the advantages of minimally invasive and angle-stable internal fixation systems offers a new option for femoral neck fracture treatment. The FNS comprises fixation plates, antirotation screws, tension screws, multifunctional targeting frames, and guide wire correctors, promoting treatment efficacy through comprehensive mechanical properties such as compression, antirotation, and shear resistance [ 10 ]. Biomechanical testing and finite element analysis have shown that the FNS integrates the advantages of minimally invasive cannulated screws while preserving more blood supply to the femoral head and maintaining stability and sliding compression, similar to dynamic hip screws (DHSs) [ 11 , 12 ]. However, there is limited scholarly research on the sensitivity of the femoral neck system (FNS) and cannulated cancellous screws (CCSs) with respect to the Pauwels angle.

We conducted a retrospective statistical analysis of clinical data from January 2020 to December 2023, comprising 38 cases of internal fixation surgery for femoral neck fractures at our institution. We compared the short-term clinical efficacy of the femoral neck system (FNS) with that of cannulated cancellous screws (CCSs) in the treatment of femoral neck fractures. Furthermore, we explored the biomechanical differences between the two internal fixation methods for treating femoral neck fractures with different Pauwels angles. While the results of simulation experiments may not necessarily reflect reality, they can indicate the mechanical trends of different experimental subjects. Huang et al. [ 13 ] compared the mechanical differences between FNS and CCSs at Pauwels angles of 55°, 65°, and 75° and reported that FNS exhibited superior anti-displacement stability to CCS at 55° and 65°. We hypothesized that the superior mechanical performance of FNS may be related to variations in the Pauwels angle. Clarifying this mechanical feature may help increase our understanding of the value of FNS in terms of structural stability and anti-hip varus. These findings provide compelling evidence for objectively evaluating the role of FNS in treating femoral neck fractures.

Materials and methods

All methods in this study were conducted in accordance with relevant guidelines and regulations. All experimental protocols were approved by the Institutional Ethical Review Board of Zhangjiagang Fifth People’s Hospital (L2024004).

Clinical research

Inclusion and exclusion criteria.

The inclusion criteria were as follows: (1) normal hip joint function on the injured side prior to injury; (2) fresh femoral neck fracture within 3 weeks; (3) age at injury ≤ 75 years; (4) willing to undergo FNS or CCS treatment; and (5) complete follow-up data.

The exclusion criteria were as follows: (1) concurrent severe medical conditions; (2) open fractures or pathological femoral neck fractures; (3) concurrent significant vascular, nerve, or organ injuries; (4) preexisting abnormal hip joint function; and (5) incomplete follow-up data.

Patient baseline data

A retrospective analysis of the clinical data of patients with femoral neck fractures treated in our hospital from January 2020 to December 2023 was conducted, with a total of 38 patients meeting the aforementioned criteria included in the study. Seventeen patients were treated with FNS fixation based on the results of doctor‒patient communication, and 21 patients were treated with CCS fixation. The general preoperative data of the two groups of patients are shown in Table  1 . There were no statistically significant differences in age, sex, body mass index (BMI), cause of injury, side, Garden classification, or Pauwels classification between the two groups ( P  > 0.05).

Surgical methods

After general anaesthesia combined with sciatic nerve block anaesthesia, the patient lay supine on the traction bed. Closed reduction is attempted under fluoroscopy, and if unsuccessful after three attempts, Kocher’s needle is used for percutaneous leverage reduction, followed by open reduction through a small incision. Once satisfactory reduction is achieved under fluoroscopy, the traction bed maintains the reduction, and surgical procedures are performed.

FNS Group: Starting from the centre of the lesser trochanter plane, a 4-cm lateral longitudinal incision was made to expose the lateral aspect of the femur. A guide pin was inserted at an angle of 130° between the centre plane of the lesser trochanter and the femoral shaft, ensuring under fluoroscopy that the guide pin was centrally located in the femoral head and 5 mm below the cartilage. After depth measurement, a cannulated drill was used to create a medullary canal pathway, and a dynamic rod was inserted along the pathway to a depth of 5 mm below the cartilage, followed by removal of the central guide pin. A lateral sleeve plate was then inserted and snugly fit against the femoral shaft, with locking screws inserted along the plate. Using an anti-rotation guide, holes were drilled, and anti-rotation screws were inserted. If there was any detachment at the fracture ends under fluoroscopy, traction was released, and the black nut was rotated counterclockwise for intraoperative compression. If there was no detachment, the handle was slid downward, the wound was irrigated, and layered closure was performed.

CCS Group: Approximately 2 cm below the greater trochanter on the lateral cortex, a percutaneous incision was made parallel to the long axis of the femoral neck for the insertion of the first guide pin. Under fluoroscopy, the anteroposterior view shows the image close to the superior aspect of the femoral cortex, and the lateral view aligns with the midpoint of the femoral neck. The pin was advanced to 5 mm below the cartilage. Using a parallel guide, the second and third guide pins were inserted, closely following the anterior and posterior walls of the femoral neck and creating a triangular arrangement with the three guide pins. Hollow drills were used along the guide pins to create holes, and three hollow screws were inserted along the guide pins. Once fluoroscopy confirmed satisfactory screw positions, the guide pins were removed, the wound was irrigated, and layered closure was performed.

Perioperative management

Postoperatively, antibiotics were administered for prophylaxis for 24 h. Low-molecular-weight heparin sodium anticoagulation therapy was initiated 12 h postoperatively. On the second postoperative day, intravenous pumps were used to prevent thrombosis formation, and muscle contraction exercises of the affected limb were initiated along with passive knee and hip joint movements. Gradual sitting in bed was started within two weeks postoperatively, and non-weight-bearing activities were recommended for the first three months. The timing for abandoning crutches and walking without support was determined on the basis of imaging assessment of fracture healing within 3 months postoperatively.

Establishment of finite element models

General information.

The orthopaedic clinic recruited a 50-year-old male volunteer with a height of 170 centimetres and a weight of 72 kg. The volunteer had no history of systemic disease, and there was no history of hip joint injury or surgery. Physical examinations and radiological assessments ruled out acute or chronic hip joint diseases. The volunteer provided informed consent for participation in this study and signed the informed consent form.

Establishment of the proximal femoral model and fracture model

The volunteers were positioned in a supine neutral posture, with both lower limbs relaxed and the pelvis leveled. The left hip joint was scanned via a 64-row CT scanner (GE Healthcare, USA). The CT images were stored in DICOM format and imported into the reverse modelling software Mimics 19.0 (Materialise, Belgium). Appropriate grayscale values were selected to distinguish bone and surrounding soft tissues. Commands such as region growing and mask editing from the tool panel were utilized to generate a three-dimensional model of the proximal femur. The model was saved as an STL file and imported into Geomagic Wrap 2017 (Geomagic, USA) software for smoothing, mesh division, and surface fitting. The skeletal solid model was constructed and saved as an IGS file. Next, the IGS femoral component was loaded into Pro/E 5.0 software (PTC, USA). A reference horizontal plane was established through the centre of the femoral head, and secondary reference planes were created at 30°, 40°, 50°, 60°, 70°, and 80° angles relative to the horizontal plane. The proximal femur model was then segmented via the secondary reference planes at various angles to simulate Pauwels type II-III femoral neck fractures.

Internal fixation model establishment and simulated surgery

The product manuals of the femoral neck system (FNS) provided by the American company Synthes and the cannulated cancellous screws (CCSs) offered by China Kangli Orthopaedic Instrument Co., Ltd., were referenced. Using Pro/E 5.0 software, models of both FNS and CCSs were separately created. The femoral neck system consists of four components: a plate, a bolt, an antirotation, and a locking nail. The locking plate serves as a 130° angle stabilizing device, and the locking nail has a diameter of 5 mm. The bolt has a length of 90 mm, a diameter of 8 mm, and a round head and is threadless. The anti-rotation component has a diameter of 6 mm, and after bolt tightening, it enhances the rotational resistance, improving the stability of the device. Each cannulated cancellous screw has a total length of 84 mm, a diameter of 4.2 mm, and a thread length of 22 mm. The established models of the two internal fixation systems and fracture models with different Pauwels angles were loaded into the assembly system of Pro/E 5.0 software for Boolean operations. After the overlapping geometric entities were removed, various types of fracture-internal fixation models were obtained. The assembly models were saved as Parasolid files separately (Fig.  1 ).

Finite element model after assembly of two kinds of internal fixation and different fracture angles of femoral neck fracture. FNS stands for femoral neck system. CCS stands for cancellous screws

Mesh division and material properties

The Hypermesh 2014 software (Altair, USA) was used to open the fracture-internal fixation assembly file in Parasolid format. After completing geometric cleaning, tetrahedral elements are employed to mesh and discretize the assembly model. Typical four-node tetrahedral elements (T4) are used for meshing. Each part within the models is exported in INP format and saved, and mesh models for different assemblies are obtained.

The parts in the INP format are imported into Abaqus 6.14 software (Dassault, France) for material assignment. In this work, the internal fixation metal components are simplified as isotropic linear elastic materials. Due to the uneven distribution of material in the femur, referring to the results of previous studies, material assignment for each element is performed individually on the basis of the grayscale value formula. The apparent density [ \(\:\rho\:(Kg/{m}^{3})\) ] and Young’s modulus [E(MPa)] of the bone are calculated from the HU values of the CT scans (with water density as the reference for zero calibration) according to the following formula [ 14 ]:

The material details of each component are shown in Table  2 .

Load and boundary condition settings

In research conducted by Freitas et al. [ 15 ], a load equivalent to the force exerted while standing on a single leg was applied to the corresponding cartilage surface of the femoral head, producing a joint reaction force of 1800 N, α = 69° and β = 7° (Fig.  2 ). To prevent femoral motion during the analysis process, the distal end of the femur was constrained in all directions of freedom [ 16 ]. Frictional contact conditions were established, with a friction coefficient of 0.46 between the fracture ends, 0.42 between the bone and the implant, and 0.2 between the implants [ 17 ].

Boundary conditions and load setting pattern diagram

A 54-year-old woman in the FNS group experienced left hip pain and limited mobility after being hit by a motor vehicle. ( a ) Preoperative radiographs showed a left femoral neck fracture (Garden IV, Pauwels III). ( b ) Postoperative anteroposterior and lateral X-rays demonstrated satisfactory fracture reduction and an acceptable position of the internal implant. ( c , d ) Anteroposterior X-rays at 3 and 12 months postoperatively revealed fracture healing. Another 50-year-old male in the FNS group developed left hip pain and restricted movement following a fall. ( e ) Preoperative radiographs indicated a left femoral neck fracture (Garden III, Pauwels II). ( f ) Postoperative anteroposterior and lateral X-rays showed satisfactory fracture reduction and an acceptable position of the internal implant. ( g , h ) Anteroposterior X-rays at 3 and 20 months postoperatively displayed fracture healing. In the CCS group, a 52-year-old male experienced right hip pain and restricted movement after being struck by a heavy object. ( i ) Preoperative radiographs revealed a right femoral neck fracture (Garden IV, Pauwels II). ( j ) Postoperative anteroposterior and lateral X-rays demonstrated satisfactory fracture reduction and an acceptable position of the internal implant. ( k , l ) Anteroposterior X-rays at 3 and 17 months postoperatively showed fracture healing. Another 63-year-old female in the CCS group developed left hip pain and restricted movement after a fall. (m) Preoperative radiographs indicated a left femoral neck fracture (Garden IV, Pauwels II). ( n ) Postoperative anteroposterior and lateral X-rays showed satisfactory fracture reduction and an acceptable position of the internal implant. ( o , p ) Anteroposterior X-rays at 3 and 12 months postoperatively displayed fracture healing

Convergence test

In this study, we conducted convergence tests using tetrahedral meshes with three resolutions. The results indicate that the equivalent stress values calculated with Mesh2 are close to those obtained with Mesh1. Accordingly, the femur and internal fixation meshes were further subdivided into sizes ranging from 0.5 to 1.0 mm to generate meshes and elements. The element and node counts for the three finite element models are presented in Table  3 .

Observation indicators

Clinical indicators.

Postoperatively, we conducted follow-ups on patients for 12 ± 6 months. Records were made and compared between the two groups of patients for surgical time (from the start of surgery to skin closure), blood loss, incision length, intraoperative fluoroscopy frequency, length of hospital stay, time to fracture healing, Harris hip function score at the last follow-up, pain-related VAS score, changes in the hip internal rotation angle, and femoral neck shortening length (the difference in femoral head position between immediate postoperative and last follow-up radiographs) [ 18 ]. Routine postoperative radiographs were used to assess fracture reduction quality (Grade I: AP 160°, Lateral 180°; Grade II: AP 155°, Lateral 180°; Grade III: AP < 155° or Lateral > 180°; Grade IV: AP < 150°, Lateral > 180°; among these, Grades III and IV are considered to indicate poor reduction quality [ 19 ]), healing status, and internal fixation position. The complications considered included incisional infection, loosening or failure of internal fixation, nonunion of fractures (defined by the U.S. Food and Drug Administration as no significant change in the fracture gap after 9 months postfracture or 3 consecutive months), and femoral head necrosis.

FEA indicators

Comparisons were made between two types of internal fixation in different femoral fracture models, including maximum stress on the proximal femoral fracture fragment (predicting the risk of secondary fractures), maximum displacement, and internal rotation angle (spatial indicators predictive of prognosis), maximum relative displacement at the fracture site (assessing the risk of nonunion, this practical approach has been used in our study of fracture surface distance measurements [ 20 ]), maximum stress on internal fixation (assessing the risk of failure), stiffness, and maximum displacement of internal fixation (assessing stability). Additionally, observing femoral displacement clouds, displacement, and stress clouds via the two internal fixation methods can clarify the displacement and stress distributions.

Statistical analysis

Continuous variables are presented as the means ± standard deviations (SDs). The normality test uses the Shapiro‒Wilk test to determine whether the data meet the application conditions of the Student’s t test. If the data do not conform to a normal distribution, consideration is given to using a nonparametric alternative method. The data were assessed via Student’s t test. Categorical variables were analysed via the chi-square test. The Mann‒Whitney U test was employed for ranked data. All the statistical analyses were conducted via SPSS 26.0 (SPSS Inc., Chicago, IL, USA). A significance level of p  < 0.05 was considered statistically significant.

Clinical outcomes of the two surgical procedures

In total, 38 patients under the age of 75 years were enrolled, with surgeries performed via the FNS method in 17 patients and the CCS method in 21 patients. The follow-up duration ranged from 3 to 22 months (mean 6.3 ± 5.2 months). The analysis results are as follows (Table  4 ).

The operative time, blood loss, incision length, and incidence of complications were not significantly different between the two groups ( p  > 0.05). However, patients receiving FNS treatment had a lower fluoroscopy frequency (15.1 ± 3.5 vs. 18.6 ± 5.0, p  = 0.019) and shorter hospital stays (12.5 ± 3.3 vs. 16.4 ± 5.4 mL, p  = 0.014). The fracture healing time in the FNS group was 3.8 ± 0.8 months, which was significantly shorter than that in the CCS group (5.4 ± 3.9 months; p  = 0.002).

The HHS of the FNS group was significantly greater than that of the CCS group (89.2 ± 4.0 vs. 83.6 ± 4.7, p  < 0.001), whereas the VAS pain score at the last follow-up was lower in the former group than in the latter group (0.9 ± 1.1 vs. 2.0 ± 1.4, p  = 0.014).

The change in NSA was lower in the FNS group than in the CCS group (1.5 ± 1.7 vs. 2.9 ± 1.9°, p  = 0.021). Both groups experienced femoral neck shortening postoperatively. Femoral neck shortening was significantly less common in the FNS group than in the CCS group (1.4 ± 1.4 mm vs. 4.2 ± 2.7 mm, p  < 0.001).

Comparison of the maximum stress in the proximal fracture fragment

The maximum stress measurements of the proximal femoral fractures in the different models are shown in Fig.  4 a. The maximum stress of the proximal fracture in the CCS group was always greater than that in the FNS group. From the perspective of the changing trend, the maximum stress of the former decreased with increasing PauWels angle, rebounded to the maximum value after 60°, and then decreased. The CCS group achieved the maximum value of 242.4 MPA when the Pauwels angle was 70°, whereas the maximum stress of the latter increased slowly with increasing PauWels angle, and the maximum value of 127.0 MPa was obtained at 70°. The risk of fatigue fracture of the proximal femur in the FNS group was lower than that in the CCS group.

Biomechanical properties comparison in different finite element models. ( a ) Peak stress of the proximal fracture fragment; ( b ) Max displacement of the proximal fragment; ( c ) Varus angle of the proximal fracture fragment; ( d ) Max displacement of fracture surface at the broken end; ( e ) Peak stress of the proximal internal fixation; ( f ) Max displacement of internal fixation. Change (%) = (FNS value – CCS value ) / CCS value * 100%

Comparison of the maximum displacement and displacement distribution of the proximal fracture fragment

The maximum displacement of the proximal femoral fragment of the two internal fixation methods in the different fracture models gradually increased as the Pauwels angle increased, as shown in Fig.  4 b. The displacement of the proximal femoral fracture fragment in the FNS group only exceeded that in the CCS group at 60° and 70°. The numerical difference between the FNS group and the CCS group was the largest at 30°, with values of 2.6 and 2.9 mm, respectively, whereas the difference between the two groups was 80°. The minimum values were both 4.8 mm. The displacement cloud diagram shows that when the angle in the FNS group was between 30° and 60°, the transition of the equivalent displacement cloud diagram between the femoral head and the diaphysis was still gentle, indicating that the displacements of the femoral head and the diaphysis were generally coordinated, whereas during the period of 70° to 80°, the transition of the equivalent displacement cloud between the femoral head and the diaphysis was smooth. There was an obvious interruption in the diaphyseal displacement cloud map, indicating that the magnitude of femoral head displacement increased. The change trend of the femoral head displacement nephogram in the CCS group was similar to that in the FNS group, but the degree of femoral head displacement did not increase significantly until 80° was reached (Fig.  5 ). These findings indicate that the stability of FNS fixation of the proximal femur is slightly better than that of CCS fixation.

Displacement nephogram of different femoral neck fracture models

Femoral head varus angle comparison

Figure  4 c illustrates the changing trends of the femoral head varus angle in different fracture models with two types of internal fixation. As the Pauwels angle increased, both the FNS and CCS groups presented an increase in the femoral head varus angle, reaching their respective maximum values at 80°, which were 4.2° and 4.5°, respectively. The smallest difference in varus angle values between the two groups occurred at 70°, with values of 3.7° and 3.7°, respectively. These findings suggest that FNS is more effective than CCS in resisting femoral head varus.

Comparison of the maximum relative displacement of the fracture surface

We examined the maximum relative displacement between the fracture sections for the two internal fixation methods, as shown in Fig.  4 d. In contrast to the results of the comparison of the femoral head varus angle, although the relative maximum displacement of the fracture sections in both the FNS and CCS groups increased with increasing Pauwel angle, the FNS group exhibited more significant activity here. The values in the FNS group surpassed those in the CCS group, with the difference peaking at 68.9% at 60°. This reflects that FNS is less effective than CCS in stabilizing the fracture ends.

Comparison of the maximum stress and stress distributions of the two types of internal fixation

The results of the maximum stress tests for the two internal fixation methods are shown in Fig.  4 e. As the Pauwels angle increases, both internal fixation methods show an increasing trend in maximum stress. In the different fracture models, the maximum stress in the FNS group’s internal fixation exceeds that in the CCS group, with the difference peaking at 101.3% at 70°. Figure  6 displays stress contour maps for both internal fixation methods, revealing that high-stress regions for both methods appear near the fracture section. However, the FNS high-stress region is significantly more extensive than the CCS region. This suggests that the risk of failure associated with the FNS is greater than that with the CCSs.

Von Mises stress distribution diagram of different internal fixation models

Comparison of the maximum displacement, stiffness and displacement distributions of the two internal fixations

Figure  4 f shows that under the action of the load, the trends of the maximum displacement changes for the two internal fixation methods are similar to the trends in the stress changes. The maximum displacement of the FNS was only slightly greater than that of the CCS group by 0.3% at 70°, whereas in the other models, it maintained lower values. In the comparison of stiffness, the intermediate value of FNS stiffness was 572.5 N/mm, exceeding that of CCS, which was 530.2 N/mm, indicating that FNS has good structural stability (Fig.  7 ). The stress contour maps illustrate the displacement distribution for the two internal fixations (Fig.  8 ), and with reference to the femoral head displacement contour map shown in Fig.  5 , the maximum displacement occurred in the proximal region associated with the activity of the femoral head.

Comparing the stiffness between two different internal fixation strategies across six different fracture types. The dotted line represents the median values of these parameters

Displacement nephogram of different internal fixation models

In this study, we investigated the short-term efficacy of the FNS and CCSs in treating femoral neck fractures and conducted clinical follow-ups to assess joint function and radiographic data. Moreover, we explored the differences in the mechanical performance of the two internal fixation methods in treating femoral neck fractures with different Pauwels angles through finite element analysis. Our study is organized as follows. First, compared with those in the CCS group, patients in the FNS group had higher postoperative hip joint scores and less radiographic evidence of reduction loss. Second, employing finite element analysis, in addition to confirming that FNS offers better stability than CCS, we also observed that as the Pauwels angle increases, the advantages of the FNS over CCSs in terms of stability and anti-hip varus tend to diminish.

Due to the unique anatomical structure of the femoral neck, blood vessels are highly vulnerable to damage when fractures occur [ 21 ]. The success of surgery requires not only anatomical reduction but also strong internal fixation, protecting the fragile blood supply and providing a stable environment for bone remodelling, which can reduce the incidence of femoral head necrosis and nonunion [ 22 ]. There is still controversy regarding the choice of internal fixation for femoral neck fractures. Traditional internal fixation devices such as dynamic hip screws and hollow pressure screws have a relatively high rate of complications, affecting patient prognosis and quality of life. To meet clinical needs, new internal fixation devices must inherit the advantages of traditional devices and improve upon their shortcomings. The FNS, as a plate-screw system, provides effective angular and rotational stability through the design of antirotation and locking screws [ 9 ], thus achieving stronger fixation. In clinical studies, the FNS has been shown to be an effective treatment for Pauwels III fractures, with faster recovery rates and fewer complications [ 23 ]. With the introduction of the concept of rapid recovery, an increasing number of hip fracture patients are recommended for early weight-bearing exercises. Evidence from cellular, animal, computer model, and clinical studies has shown that mechanical loading from weight-bearing aids in accelerating fracture healing [ 24 , 25 ]. Early weight-bearing can reduce hospital stay, postoperative pain, and mortality rates while improving joint function [ 26 , 27 ]. However, due to concerns about the fixation strength and reliability of internal fixation devices, many conservative doctors still recommend prolonged bed rest. Recently, Kenmegne et al. [ 28 ] conducted a series of clinical studies and reported that the fracture healing time in the FNS group was significantly shorter than that in the CCS group ( p  < 0.05). FNS, as a novel internal fixation device, has a greater design strength than CCS and offers better stability and lower failure risk in the face of high-stress fractures, such as unstable fractures [ 28 ]. Zhang et al. [ 29 ] reported through a meta-analysis that patients in the FNS group were able to mobilize earlier than those in the CCS group. Additionally, the shorter fracture healing period observed in the FNS group can provide additional confidence in rehabilitation, thus encouraging early weight-bearing and improving patient outcomes. Similar to the results of the previously published meta-analysis [ 30 ], the results of this study show that, compared with the CCS group, the FNS group had less intraoperative blood loss, shorter incisions, significantly reduced intraoperative fluoroscopy times, significantly shorter hospital stays, and earlier postoperative full weight-bearing walking times. Although a large amount of research shows that compression and micromotion at the fracture site can promote fracture healing, this healing theory for the femoral neck should be based on effective control of shear forces [ 10 , 13 , 31 ]. Unlike the parallel placement of hollow screws, the unique nail plate locking and angular structure of FNS prevent sliding of the femoral head, providing greater stability to the femoral head and effectively preventing femoral neck shortening. The antirotation screw design in the FNS, with a 7.5° angle to the tension screw, can effectively resist rotation, provide good biomechanical stability, prevent the “Z” effect on the femoral head, and effectively resist vertical shear forces. The design of the tension screw tip thread firmly grasps the fracture end, providing strong active compression during surgery; linear insertion maintains effective fracture reduction; and providing angular stability effectively prevents reduction loss [ 5 ].

Femoral neck shortening commonly occurs after femoral neck fractures, potentially leading to symptoms such as limb pain, limping, and fixation failure. The International Society for Fracture Repair acknowledges that effective resistance to varus and rotational forces is necessary for treating femoral neck fractures and that appropriate axial stress facilitates fracture healing [ 32 ]. Hollow screw designs allow compression through sliding of fracture fragments during healing; however, excessive absorption of fracture ends, especially in cases of comminuted fractures, can lead to significant shortening of the femoral neck or even screw cut-out. Stoffel et al. [ 9 ] reported that over half of patients experienced femoral neck shortening exceeding 5 mm, with nearly one-third experiencing shortening greater than 10 mm, severely impacting limb function. In our study, both groups had femoral neck shortening of less than 5 mm, with FNS demonstrating superior fixation performance and stronger stability, resulting in significantly less femoral neck shortening than that in the CCS group. However, some degree of shortening still occurred, with good hip joint mobility postoperatively. Hu et al. [ 33 ] compared the efficacy of FNS and three hollow screws and reported that both groups experienced femoral neck shortening postoperatively, with the FNS group exhibiting significantly less shortening than the three hollow screws group did, which is consistent with our findings and literature reports. Thus, the FNS system provides greater stability at the fracture site. Additionally, the incidence of complications was lower in the FNS group than in the CCS group in this study. Similar to our study, Tang et al. [ 34 ] compared FNS and inverted hollow cancellous screws and reported that angular fixation devices may have better resistance to varus deformity and micromotion than traditional triangular screws. The FNS has yielded promising clinical results in resisting femoral neck shortening and complications.

The previous text reviewed and analysed the efficacy and pros and cons of the FNS and CCSs in fixing femoral neck fractures, highlighting the importance of comparative evaluation for clinical application. To further explore the mechanical differences between these two internal fixation methods in treating femoral neck fractures with different Pauwels angles, we designed a finite element simulation experiment. Compared with that in the CCS group, the maximum stress value of the proximal fracture block in the FNS group was lower, with the former fluctuating between 120 and 240 MPa and the latter fluctuating around 120 MPa. These findings indicate that, compared with the FNS group, the CCS group has a greater risk of femoral head fracture and collapse. When the FNS is used, the risk of internal fixation loosening, cutting, and femoral fractures is minimal, effectively protecting the integrity of the bone near the fracture. This trend aligns with the finite element study conducted by Xia et al. [ 35 ], which simulated a Pauwels angle of 70° Pauwels III femoral neck fracture and observed the biomechanical performance of different devices after applying a load of 2100 N. The results revealed that the maximum stress value of the bone in the FNS group was 107.9 MPa, whereas it was 486.3 MPa in the CCS group. In the present study, relative to the proximal bone block, the internal fixation device resulted in greater stress. With increasing Pauwels angle, the maximum stress of both internal fixations tended to increase. In the different fracture models, the maximum stress of internal fixation in the FNS group exceeded that of the CCS group, with the difference reaching a peak of 101.3% in the Pauwels 70° model. The stress distribution was mainly concentrated on the screw surface near the fracture line, with the FNS group bearing the maximum stress among the groups. Although the FNS bears greater stress, the internal fixation displacement test revealed that the FNS is more stable overall than the CCSs, with a stiffness exceeding that of the latter by 7.9%. This finding indicates that FNS has greater strength after internal fixation, making it less prone to deformation, loss of reduction, and other complications. The superiority of the femoral neck internal fixation system over hollow screws can be explained as follows. Within the femoral neck internal fixation system, dynamic hip screws and locking antirotation screws provide robust angular support and effectively maintain the fracture in the proper position. Compared with the use of a hollow screw in conjunction with a dynamic hip screw, the femoral neck internal fixation system locks the locking antirotation screw with the main screw more securely, forming a unified whole and providing better antirotation action. However, inserting a 5-mm-diameter locking screw at the distal end of the locking plate can integrate the locking plate and femoral shaft into a single entity. Therefore, biomechanically, the femoral neck internal fixation system offers better anchoring than the hollow screw fixation system does, helping to reduce stress on the proximal femur and decrease displacement of both the femur and internal fixation implants, thereby creating a favourable mechanical environment for fracture healing.

Mechanical experiments indicate that, compared with CCSs, the FNS is more effective in preventing femoral neck shortening [ 9 ]. In the face of unstable femoral neck fractures, CCSs result in a lower ultimate load-bearing capacity [ 36 ]. With an increase in the Pauwels angle, the shear force becomes the primary external force leading to internal fixation failure [ 37 ]. CCSs lack sufficient angular stability and have a relatively poor ability to withstand shear stress. In finite element analysis of Pauwels III fractures, the distal double-hole FNS demonstrated stronger biomechanical stability and lower failure risk than the CCSs [ 38 ]. In this study, we extensively compared the differences in the femoral head varus angle and displacement between the FNS and CCSs in femoral neck fractures with different Pauwels angles. Similar to previous reports, we found that the FNS indeed has some advantages in resisting femoral head varus and constraining displacement. However, between Pauwels angles of 30–70°, the advantage of the FNS gradually diminishes with increasing Pauwels angle, reflecting that the superiority of the FNS over CCSs is conditionally limited and that the increase in shear stress poses a significant challenge to the stability of FNS. Interestingly, as the Pauwels angle increased, the separation displacement of the upper wall of the femoral neck also increased, with the FNS resulting in greater separation displacement than CCSs. Given that the FNS provides central fixation while CCSs offer distributed fixation, the lever arm of the FNS causing separation of the fracture ends is greater than that of CCSs. The same physiological load can result in greater separation displacement of the fracture ends in the FNS group. Although this difference has not been clinically confirmed to have adverse effects on fracture healing, our study indicates that the FNS is not a flawless device.

This study has several limitations: (1) The clinical research involved retrospective analysis, with nonrandom patient selection, potentially introducing selection bias. In the measurement of femoral neck shortening, errors may exist due to nonstandard patient positioning during X-ray imaging. The duration of FNS surgery was relatively short, and the follow-up period in the study was insufficient, providing only early reports on postoperative complications such as femoral neck shortening, nonunion, and avascular necrosis of the femoral head. Further long-term efficacy assessments require additional follow-up observations. (2) The finite element modelling method treats fractures as flat surfaces, whereas real fracture ends are often jagged and uneven contact surfaces, resulting in some disparity between the model and reality. Furthermore, whether the mechanical conclusions of the CCS obtained from this study can cover all clinical application scenarios still requires further verification. (3) The experiment applied a single load (joint reaction force) without considering the tensile effects of muscles around the greater and lesser trochanters. Future research should consider the impact of muscles around the hip joint on femoral loading.

In summary, the FNS demonstrates superior clinical efficacy compared with CCS in treating femoral neck fractures, with the former being more beneficial for improving hip joint function. Biomechanical research results confirm the advantages of FNS in terms of structural stability and anti-hip varus effects. However, as the Pauwels angle increases, the superiority of the FNS over CCSs is conditional, as significant shear stress still poses a challenge to the fixation effect of the FNS.

Data availability

No datasets were generated or analysed during the current study.

Abbreviations

• Femoral neck system
• Cannulated cancellous screws

dynamic hip screws

Finite element analysis 3D: Three-dimensional

Harris Hip Score

Visual Analog Scale for Pain

Neck shaft angle

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Acknowledgements

We thank the School of Medicine of Tongji University, Shanghai SIEG Machinery Co., Ltd. and Zhangjiagang First People’s Hospital for theoretical guidance and technical support.

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Department of Orthopedic, Zhangjiagang fifth People’s Hospital, No.120 Lefeng Road,, Zhangjiagang, 215600, Jiangsu province, China

Zhi Xu, Feng Huang, Yu Gong & Hao Zhou

Department of Orthopedic, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, 200120, China

Department of Orthopedics, Ningxia Chinese Medicine Research Center, Ningxia Autonomous Region, Yinchuan, 750021, China

Research and Development Department, Shanghai SIEG Machinery Co., Ltd, Shanghai, 200000, China

Jinxiang Zhao, Yiping Shao & Shuping Fang

Department of Orthopedic, The First Affiliated Hospital of Wannan Medical College, Wuhu, 241000, Anhui province, China

Department of Orthopedic, Zhangjiagang First People’s Hospital, No.68 Jiyang West Road Zhangjiagang 215600, Zhangjiagang, 215600, Jiangsu province, China

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Z.X. and F.H. contributed to the research design and implementation, and made in-depth discussions on research hotspots and technical difficulties. J.S., J.X.Z., Y.P.S. and S.P.F. contributed to model development and data acquisition. J.J.L., Z.R.W and Y.G. contributed to clinical data collection and data acquisition. Z.X., H.Z. and S.J.T. analyzed and interpreted the data and drafted the manuscript. All authors approved the final version of the manuscript.

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Correspondence to Hao Zhou or Shoujin Tian .

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Xu, Z., Sun, J., Li, J. et al. Comparative analysis of the femoral neck system (FNS) vs. cannulated cancellous screws (CCS) in the treatment of Middle-aged and elderly patients with femoral neck fractures: clinical outcomes and biomechanical insights. BMC Musculoskelet Disord 25 , 735 (2024). https://doi.org/10.1186/s12891-024-07863-7

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DOI : https://doi.org/10.1186/s12891-024-07863-7

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Mortality after admission to hospital with fractured neck of femur: database study

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• Michael J Goldacre , director ( michael.goldacre{at}dphpc.ox.ac.uk ) ,
• Stephen E Roberts , statistician ,
• David Yeates , computer scientist
• Unit of Health-Care Epidemiology, Department of Public Health, Institute of Health Sciences, University of Oxford, Oxford OX3 7LF
• Correspondence to: M J Goldacre
• Accepted 21 March 2002

The death rate within one year of fractured neck of femur is typically reported as between 20% and 35%. 1 – 3 Performance indicators based on mortality after hospital admission for such fractures have been promoted. 4 The only measure of mortality in routine hospital statistics, however, is “in-hospital mortality”—death during the initial admission for the fracture. We analysed inpatient statistics that had been linked to death registration data in the former Oxford NHS health region (population 2.5 million) from 1994 to 1998.

Methods and results

We selected emergency admissions in people aged 65 years and over who had been admitted to eight main acute trusts and for whom fractured neck of femur was the principal diagnosis (international classification of diseases, ninth revision (ICD-9), codes 820, 821.0, and 821.1). We calculated standardised mortality ratios after fracture by applying the age and sex specific mortality in five-year age groups in the whole population of the region (“standard” population) to the number of people with fractured neck of femur in the equivalent age and sex strata, in successive months up to one year after fracture. For each hospital, we calculated case fatality rates for in-hospital deaths within 30 days and for all deaths within 30, 90, and 180 days of admission. We calculated age and sex standardised case fatality rates for each hospital by applying the age and sex specific rates in each hospital to the number of people in each age-sex stratum in the total inpatient population. We calculated case fatality rates separately for deaths certified as fractured femur and for all deaths.

In total, 8148 people aged 65 and over were included (80.2% women; mean (SD 7.2) age 82.2 years). In the first month after fracture the standardised mortality ratio was 1246 (95% confidence interval 1164 to 1331; general population 100). The standardised mortality ratios, adjusted for person months at risk, were 451 (397 to 509) in month 3, 238 (197 to 283) in month 6, and 187 (149 to 230) in month 12. Fractured femur was certified as the underlying cause in 16%, and as a cause anywhere on the death certificate in 43%, of deaths occurring in the first month.

As the table shows, the mortality ranking of hospitals varied with definitions and time frames. Death rates for all causes showed that three hospitals (B, C, and H) had significantly lower rates than hospital A for in-hospital mortality within 30 days, and two (B and C) had significantly lower rates for 30 day mortality regardless of place of death. By 90 and 180 days, differences between hospitals were not significant. Hospitals also changed rank depending on whether deaths from all causes or only those certified as fractured femur were included (table).

Case fatality rates per 100 admissions and ranks (95% confidence intervals) for each hospital, adjusted for age and sex, showing different definitions and time intervals from admission

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The standardised mortality ratios show that mortality is much higher in people after fractured neck of femur than in the general population of comparable age, and they remain raised for many months after fracture. The persistently increased standardised mortality ratio may indicate continuing sequelae of the fracture or that people fracturing their neck of femur are more frail and ill than the general population of similar age.

Measures of prognosis after fracture and comparisons between hospitals are substantially affected by whether death registration data are included, whether time intervals are extended beyond 30 days, and whether deaths that are not certified as fractured femur are included. When death registration data are available, one option is to confine analyses of mortality to the deaths attributed by the certifying clinician to the fracture. Our study confirms, however, that the fracture is often not recorded on death certificates even when death occurs soon after fracture. 5 Studies of mortality after fractured femur will be misleading unless they include deaths after discharge from the initial admission and consider all causes of death.

Acknowledgments

We thank Pamela Evans for preparing the manuscript.

Contributors MJG designed the study and jointly wrote the manuscript. SER contributed to the design, analysed the data, and jointly wrote the manuscript. DY extracted the data, contributed to the design, and commented on the manuscript. MJG and SER are guarantors for the paper.

Funding SER receives funding from the Department of Health (the views expressed in this paper are those of the authors and not necessarily those of the Department of Health). The Unit of Health-Care Epidemiology is funded by the South East regional office of the NHS Executive.

Competing interests None declared.

• Freeman CJ ,
• Camilleri-Ferrante C ,
• Palmer CR ,
• Laxton CE ,
• Parker MJ ,
• Boereboom FT ,
• Raymakers JA ,
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• Goldacre MJ

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Neck of femur fractures treated with the femoral neck system: outcomes of one hundred and two patients and literature review

Affiliations.

• 1 Academic Department of Trauma and Orthopaedic Surgery, School of Medicine, University of Leeds, Leeds, UK. [email protected].
• 2 Department of Orthopaedic Surgery, Shaare Zedek Medical Center, Jerusalem, Israel. [email protected].
• 3 Department of Orthopaedic Surgery, Shaare Zedek Medical Center, Jerusalem, Israel.
• 4 Department of Orthopaedic Surgery, Shamir (Assaf Harofeh) Medical Center, Zerifin, Israel.
• 5 Academic Department of Trauma and Orthopaedic Surgery, School of Medicine, University of Leeds, Leeds, UK.
• 6 NIHR Leeds Biomedical Research Center, Chapel Allerton Hospital, Leeds, UK.
• PMID: 35538322
• PMCID: PMC9372123
• DOI: 10.1007/s00264-022-05414-0

Introduction: The recently developed femoral neck system (FNS) for treatment of femoral neck fractures (FNF), comprises theoretical biomechanical advantages compared to other implants. The aim of this study was to validate the safety and to report outcomes of patients treated with the FNS.

Method: A retrospective multicentric analysis of patients treated by FNS with a minimum of three months of follow-up. Details analysed from three medical centres were operative duration, estimated blood loss, initial hospitalisation duration, fixation quality as well as complications and reoperation rate. Patients who had revision surgery were compared to all other patients to identify risk factors for failure. In addition, a literature review was performed to analyse data on FNS clinical implementation and patient's outcomes. The two data sets were combined and analysed.

Results: One-hundred and two patients were included in this study cohort with an average follow-up of seven months (range 3-27). Ten papers were included in the literature review, reporting data on 278 patients. Overall, 380 patients were analysed. Average age was 62.6 years, 52% of the fractures were classified as Gardens 1-2. Overall, the revision rate was 9.2% (14 patients diagnosed with cut-out of implant, 10 with AVN, 8 with non-union and 8 with hardware removal). For the 102 patients in the cohort risk factors for reoperation included patients age, surgeon seniority and inadequate placement of the implant.

Conclusion: This study shows that FNS is a safe treatment option for FNF. Intra-operative parameters and failure rates are comparable to previously reported rates for this implant and other frequently used implants.

Keywords: Complications; FNS; Femoral neck fractures; Femoral neck system; Revision rate; Risk factors.

© 2022. The Author(s).

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Conflict of interest statement

The authors declare no competing interests.

• Comment on Davidson et al.: Neck of femur fractures treated with the femoral neck system: outcomes of one hundred and two patients and literature review. Yu X, Yin H. Yu X, et al. Int Orthop. 2022 Sep;46(9):2117-2118. doi: 10.1007/s00264-022-05452-8. Epub 2022 May 25. Int Orthop. 2022. PMID: 35610388 Review. No abstract available.

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The presence of a sinus tract is associated with reinfection after two-stage revision surgery for prosthetic hip joint infection: a case-control study

Department of Orthopedic Surgery, Peking Union Medical College, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing, 100730 China

Zhaojing Yin

Xisheng weng, wenwei qian, associated data.

Raw data and materials of this study is kept in the local server of Peking Union Medical College Hospital for the purpose of safety and confidentiality. Our data are available upon request for non-commercial research purpose.

Reinfection rates after two-stage revision (TSR) for prosthetic joint infection (PJI) range from 7.9 to 14%. Many factors, including sinus tracts, are associated with reinfection after this procedure. This study aimed to delineate whether the presence of sinus tract could increase reinfection rate after TSR and to investigate other potential risk factors for reinfection after TSR.

We conducted a case-control study by retrospectively reviewing patients who underwent TSR for prosthetic hip joint infection from 2002 to 2022. The case group included patients who developed reinfection after TSR, while the control group consisted of patients who did not experience reinfection. PJI and reinfection after TSR were defined based on Delphi-based international consensus criteria. Patient demographics, past medical history, clinical manifestations, laboratory results, interval between stages, microbiological culture results were collected. Univariate analyses were utilized to assess the effect of sinus tract on reinfection and to identify other risk factors for reinfection after TSR.

Six patients with reinfection after TSR were included as the case group and 32 patients without reinfection were in the control group. Significant difference was observed in percentage of patients with sinus tracts between the two groups (67% in the case group versus 19% in the control group, p  = 0.031, OR = 8.7). Significant difference was also found in percentage of patients with positive cultures of synovial fluid and synovium harvested during the first-stage revision between the two groups (100% in the case group versus 50% in the control group, p  = 0.030). Additionally, patients in the case group had a significantly higher C-reactive protein (CRP) level prior to the second stage revision than that of patients in the control group (8.80 mg/L versus 2.36 mg/L, p  = 0.005), despite normal CRP levels in all patients.

Conclusions

Our study revealed that the presence of sinus tracts could significantly increase risk of postoperative reinfection after TSR. Positive cultures during the first stage revision and elevated CRP level prior to the second stage revision could also increase the risk of reinfection after TSR. Further studies with a larger sample size are required.

Trial registration

Retrospectively registered.

Introduction

Prosthetic joint infection (PJI), defined as infection involved the joint prosthesis and adjacent tissue, is one of the most devastating complications after arthroplasties. PJI can cause joint pain, fever, prothesis loosening, joint dysfunction and expose patients to risk of multiple surgeries, increasing economic cost and mortality rate [ 1 , 2 ]. PJI after total hip arthroplasty ranges from 0.8 to 2.1%, accounting for 14.8% revisions of prosthetic hip joint [ 3 – 5 ]. The International Consensus on Orthopedic Infections definition (2018) with 2 major criteria and 7 minor criteria is commonly used for the diagnosis of PJI [ 6 ]. Anemia, malnutrition, obesity, history of intra-articular injection within 3 months, prolonged operation time, and wound healing complications are all risk factors for PJI [ 7 – 10 ]. The most common pathogens in PJI is coagulase-negative staphylococci (especially Staphylococcus epidermidis), followed by Staphylococcus aureus, streptococcus species, enterococcus species, cutibacterium species, and Enterobacterales [ 11 ]. As main materials of joint prothesis, titanium (and its alloys), cobalt-chromium, various polymeric biomaterials (e.g. ceramics, hydroxyapatite, and polyethylene), and polymethylmethacrylate (PMMA) are susceptible to adhesion and colonization by biofilm-forming bacteria [ 12 ]. Besides, the rough surface of the prosthesis is also more likely to lead to bacterial adhesion [ 13 ].

PJI is challenging for orthopedists to treat due to the potential of reinfection and bone loss. For patients of acute PJI without sinus tracts and loose prothesis, debridement, antibiotics, and implant retention (DAIR) is the treatment of choice [ 14 , 15 ]. For chronic PJI, patients are often offered a one-stage or two-stage revision. One-stage revision (removal of the infected prothesis and reimplantation of a new prothesis during one procedure) is alternative for patients with intact or only slightly compromised bone and soft tissue [ 2 ]. While two-stage revision (TSR) is usually considered as the gold standard of treatment for PJI [ 16 ]. TSR consists of two separate surgeries: the first stage is to remove all the implants followed by a complete debridement of abnormal tissues and thorough irrigation. After that, an antibiotic-loaded spacer, often comprised of polymethylmethacrylate (PMMA), is inserted. Spacers can be articulated or nonarticulated, and can be prefabricated or surgeon made [ 17 , 18 ]. During the interval, around 16–18% patients might experience spacer exchange due to recalcitrant PJI [ 19 ]. After six weeks of systemic antibiotic therapy and two to eight weeks of antibiotic-free period, the spacer is removed and followed by debridement and irrigation. Then, the prosthesis is reimplanted [ 16 ]. A period of total 6–8 week interval was commonly used before removing the spacer, while the optimal timing to remove the spacer and reimplant the prothesis has not yet been defined [ 20 , 21 ].

Unfortunately, reported rate of reinfection after TSR still remained 7.9 -14% [ 22 , 23 ].Little is known about the risk factors for the recurrence of PJI after TSR, although several studies have been conducted [ 24 – 30 ]. For instance, the literatures reported that the presence of a sinus tract was an independent risk factor for recurrent infection of two-stage revision total knee arthroplasty and the first stage of TSR [ 31 , 32 ]. While these studies did not report the impact of a sinus tract on the failure of two-stage revision total hip arthroplasty.

Here, we conducted a case-control study to (1) primarily investigate whether the presence of a sinus tract is associated with reinfection after TSR for prosthetic hip joint infection, and (2) secondarily to explore positive rate of microbiological cultures and risk factors associated with reinfection. We hypothesized that the presence of a sinus tract could increase reinfection rate after TSR for PJI of hip.

Materials and methods

We retrospectively reviewed medical records of patients who underwent TSR for prosthetic joint infection (PJI) of the hip at a single medical center from 1 January, 2002, to 31 December, 2022 (Fig.  1 ). When reviewing the medical record, the diagnosis of PJI was reaffirmed using Delphi-based international consensus criteria by a 3th and 4th-year orthopedic resident, each of whom systematically learned this consensus at the start of the study (Fig.  2 ) [ 6 ]. Any discrepancy was resolved through consultation with a senior orthopedic surgeon with at least 20 years of experience. Patients (aged ≥ 18 years) diagnosed with reinfection of prosthetic hip joint after the second stage revision were included as the case group. Reinfection of prosthetic hip joint was defined according to Delphi-based international consensus criteria. The exclusion criteria were the following: (1) patients without complete medical records; (2) patients who received the first or second stage revision of prosthetic hip at another hospital; (3) patients who received two-stage revision for reasons other than PJI. The control group contained patients without recurrence of prosthetic joint infection of the hip after the second stage revisions of prosthetic hips. No recurrence of prosthetic joint infection was defined as no clinical or laboratory evidence of hip infection and no signs of prosthetic loosening. Clinical evidence includes presence of sinus tract and pain in the affected joint. Laboratory evidence of reinfection includes elevation of serum C-reactive protein (CRP), D-dimer and erythrocyte sedimentation rate (ESR).

Flowchart of patient selection process

Delphi-based international consensus criteria

During the first-stage revision, a handmade articulating spacer composed of bone cement and vancomycin was inserted in all patients [ 17 ]. After the first stage, systemic anti-infection therapy was administered according to antimicrobial susceptibility tests. Patients were given antibiotics intravenously for two weeks during hospitalization and oral antibiotics for four weeks after discharge. Patients with negative cultures were given vancomycin and meropenem intravenously for two weeks during hospitalization and sulfamethoxazole and linezolid orally after discharge for another four weeks. Antibiotic therapy was performed for totally more than six consecutive weeks until normalization of white blood cell (WBC) count, CRP and ESR. Then, more than two weeks of antibiotic holiday period followed until the second-stage revision was performed.

Data collection

Patients’ medical records during hospitalization were reviewed to collect the demographic characteristics, past medical history, operation information, laboratory test results, clinical manifestations, and any complications related with revision surgeries. Clinical manifestations including arthralgia, joint swelling, the presence of sinus tract, body temperature. Other related information, such as range of motion, change of body temperature after TSR, was collected by interviewing patients or their family members. Patients’ age, gender, body weight, body mass index (BMI), history of diabetes mellitus, history of rheumatic diseases, history of smoking, and American Society of Anesthesiologists score (ASA score) were collected as the demographic characteristics. History of rheumatic diseases was defined as the presence of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ankylosing spondylitis (AS), Sjogren’s syndrome, and antiphospholipid syndrome. The interval between the first stage revision and the second stage revision, and the history of previous surgery, infection and intraarticular injections of the affected hip joint were also abstracted and analyzed as potential risk factors. Laboratory test results included serumCRP level, WBC count, ESR and D-dimer level prior to the second-stage revision, and organism cultures during the first-stage revision. All of data were collected by two doctors separately. The primary endpoint was the difference in sinus incidence between the two groups. The secondary endpoints were differences in microbial culture positive rates, CRP levels, ESR levels, and D-dimer levels between the two groups.

Statement of human and animal rights

Ethics approval from the Institutional Review Board (No. K5245) was obtained. The clinical investigation was conducted according to the principles of the Declaration of Helsinki.

Statistical analyses

All data analyses were performed using Statistical Package for the Social Sciences (SPSS) 25.0 for windows (SPSS institute, Chicago, IL, USA). For continuous variables, Shapiro-Wilk test was used to evaluate the normality of the distribution of each parameter. Continuous variables with normal distribution were described as mean ± standard deviation (SD), and the unpaired t-test was used to assess differences between the case group and the control group in these variables. While those with non-normal distribution were presented as median and interquartile range (IQR), and the Mann-Whitney test was used. Categorical variables were described as absolute value and percentages. Comparisons of categorical variables were performed by using Fisher exact test. p value < 0.05 was considered statistically significant.

Demographic characteristics

38 patients who received two-stage revision for prosthetic hip joint infection were screened. Prior to intraarticular fluid aspiration for cytology analysis, all patients had received empiric antibiotic therapy before being transferred to our institution. The mean follow-up of the control group was 55 months (range, 19–126 months). Within these 38 patients, six patients, constituting the case group, were diagnosed with reinfection of hip joint subsequent to two-stage revision. The remaining 32 patients, who had no reinfection of prosthetic hip joint, constituted the control group. The demographic characteristics comparison between the case group and the control group is shown in Table  1 . The case group comprised three females (50%) and three males (50%) with an average age at the time of TSR of 58 ± 12 years. While in the control group, the number of females and males was 14 (44%) and 18 (56%) respectively ( p  = 0.746). And the average age at the time of TSR was 56 ± 16 years in the control group ( p  = 0.999). Average body weight was 69 ± 22 kg in the case group and 66 ± 11 kg in the control group ( p  = 0.685). As for average body mass index (BMI), it was 24.60 ± 5.03 kg/m 2 in the case group and 23.43 ± 3.31 kg/m 2 in the control group ( p  = 0.469). The number of patients with their American society of Anesthesiologists scores (ASA scores) surpassing 2 was three (50%) in the case group and eight (25%) in the control group, with no statistically significant difference observed ( p  = 0.329). In the case group, the prevalence of diabetes mellitus was observed in three patients (50%), comparing with four patients (13%) in the control group ( p  = 0.063). Three out of six patients (50%) in the case group had a history of rheumatic diseases—one with systemic lupus erythematosus (SLE) (17%), one with rheumatoid arthritis (RA) (17%), and another with ankylosing spondylitis (AS) (17%). In the control group, seven out of 22 patients (33%) had a history of rheumatic diseases, in which one patient had RA (5%), five patients had SLE (23%), and one patient had antiphospholipid syndrome (APS) (5%). Comparisons of the incidence of rheumatic disease between the two groups showed no significant difference ( p  = 0.310), either. Additionally, compared with six patients (19%) in the control group, the number of patients with a history of smoking was one (17%) in the case group without statistical difference being found ( p  = 0.999). In the control group, one patient had a history of core-decompression of the affected hip, and one patient had a history of internal fixation for a fracture of the femoral neck on his affected hip. In the case group, none of the patients had a history of surgery on the affected hip. No patient in either group had received intraarticular injections of the hip.

BMI: body mass index

ASA: American Society of Anesthesiologists

Clinical findings

Prior to the first stage revision, four patients in the case group had sinus tracts around their prosthetic hip joints (67%). While in the control group, six patients had sinus tracts, which only accounted for 19% of the group. Significant difference was found between these two groups ( p  = 0.031). We also calculated by odds ratio (OR) the impact that the presence of sinus tract has, as a risk factor, in the reinfection after TSR. A value of OR of 8.7 was revealed. Duration of interval between the first stage revision and the second stage revision was 5 (3–12) months in the case group, while in the control group, it was 7 (5–11) months ( p  = 0.245).

As for laboratory results, average albumin level in the case group was 36 ± 6 g/L, which was the same as that in the control group ( p  = 0.819). Average lymphocyte count was 1.60 ± 0.42 × 10 9 /L in the case group and 1.78 ± 0.51 × 10 9 /L in the control group ( p  = 0.424). Inflammatory indices were collected before the second stage revision, including serum C-reactive protein (CRP) level, white blood cell (WBC) count, erythrocyte sedimentation rate (ESR) and D-dimer level. Average WBC count was 7.20 ± 2.28 × 10 9 /L in the case group and 5.97 ± 1.46 × 10 9 /L in the control group, which showed no significant difference ( p  = 0.093). The case group had a significantly higher CRP level than that of the control group (8.80 (5.68–16.18) mg/L vs. 2.36 (1.10–5.6) mg/L; p  = 0.005). Median ESR in the case group was 21 (12–37) mm/H and in the control group, it was 14 (5–25) mm/H ( p  = 0.159). As for D-dimer, median level of D-dimer in the case group was 1.11 (0.55–1.46) mg/L, and in the control group, it was 0.81 (0.52–1.19) mg/L, with no significance being found (Table  2 ).

Univariate analysis

LY: Lymphocyte

WBC: White blood cell

ESR: erythrocyte sedimentation rate

CRP: C-reactive protein

As for complication related with TSR, one patient in the control group sustained dislocation on the sixth postoperative day, and a closed reduction was then performed. No aseptic loosening, spacer fracture or pulmonary embolism was observed in our study.

Microbiological findings

Samples from synovial fluid and synovium were harvested for bacteria culturing during the first stage revision. In the case group, 6 patients had positive results of microbiological cultures, accounting for 100%. Among them, 3 (50%) patients had positive cultures of staphylococcus aureus, 2 (33%) patients for methicillin resistant staphylococcus epidermidis (MRSE), and 1 (17%) patient for Proteus mirabilis. In the control group, 16 patients had positive results of bacteria cultures, accounting for 50%. Among these 16 patients, 2 (13%) patient had positive culture of staphylococcus aureus, 4 (27%) patients for MRSE, 2 (13%) patients for methicillin resistant staphylococcus aureus (MRSA), 2 (13%) patients for methicillin resistant staphylococcus coagulase negative (MRSCON), 1 (7%) patient for Escherichia coli., 1 (7%) patient for Enterobacter cloacae., 2 (13%) patients for Salmonella typhimurium, 1 (7%) patient for Klebsiella pneumoniae, and 1 (7%) patient for Acinetobacter pittii. Comparisons of the number of positive cultures between the two groups was significantly different ( p  = 0.030) (Table  3 ).

Gram +: Gram-positive bacteria

Gram –: Gram-negative bacteria

MSSA: methicillin sensitive staphylococcus aureus

MRSE: methicillin resistant staphylococcus epidermidis

MRSA: methicillin resistant staphylococcus aureus

MRSCON: methicillin resistant staphylococcus coagulase negative

Our study compared demographic characteristics, potential risk factors and microbiological characteristics between the reinfection group and the non-reinfection group, finding that patients with the presence of sinus tracts ( p  = 0.031) and positive cultures of synovial fluid and synovium harvested during the first-stage revision ( p  = 0.030) could significantly increase reinfection rate after TSR. Furthermore, the reinfection group exhibited a higher CRP level than that of the non-reinfection group, although all patients had normal CRP levels.

Diabetes mellitus was considered as the risk factor for PJI after the first-time THA [ 33 ]. In another study, HbA1c levels ≥ 7% prior to the second-stage surgery was also identified as a risk factor for reinfection [ 34 ]. In our study, the case group showed higher rate of patients with diabetes mellitus (50% in the case group versus 13% in the control group), although this difference did not reach statistical significance ( p  = 0.063). However, the p-value approached 0.05, the predetermined threshold. Besides, the duration of diabetes mellitus and the level of blood sugar in the two groups were not collected and compared, potentially confounding its effect.

Rheumatic diseases could elevate risk for PJI after total joint arthroplasty due to alterations in the immune system induced by the disease itself and use of disease-modifying antirheumatic drugs (DMARD) [ 35 – 37 ]. The present study showed a higher incidence of patients with concomitant rheumatic diseases compared to the control group, while this difference was not significant (50% in the case group vs. 22% in the control group, p  = 0.310). We supposed that patients diagnosed with prosthetic hip joint infection may inherently have a heightened prevalence of rheumatic diseases, complicating the detection of significant difference between the case group and the control group, especially when the sample size was relatively small. Furthermore, duration of rheumatic diseases, and specific dosage and type of DMARD administered to patients were not recorded in detail, which might hinder the effect that rheumatic diseases produced.

Sinus tract, defined as a draining tract extending from the infectious joint interior to the skin surface exterior, plays an important role in the diagnosis of prosthetic joint infection. Alexandra et al. conducted a retrospective study of 240 patients (including 170 knees and 70 hips) treated for PJI with intended two-stage revision trying to explore the effect of the presence of sinus tract [ 38 ]. They found that patients with sinus tracts were significantly less likely to be re-implanted compared to those without a sinus tract at presentation. But difference of the rate of reinfection between the sinus tract group and no sinus tract group was not significant. However, opposite results were shown in a retrospective cohort study conducted by Wang et al., in which researchers found that presence of sinus tract before treatment was an independent risk factor for reinfection after the first stage revision [ 32 ]. In our study, four patients had sinus tracts before TSR in the case group, accounting for 67%, while six patients had sinus tracts in the control group, accounting for 19%. A value of OR of 8.7 was calculated. Significant difference was found, indicating that presence of sinus tract before surgery can increase the risk of reinfection after TSR. We inferred that the presence of a sinus tract reflected the intensity of local inflammatory reactions and extent of infection within the local joint, which impacted the ability of local tissues to manage infection and undergo healing. Therefore, more attention should be paid to the patients with a sinus tract when TSR is intended to be performed. Additionally, during the first-stage revision surgery, it is necessary to thoroughly remove the sinus tract as well as any suspiciously infected or affected soft tissues surrounding the sinus tract.

The optimal duration of interval between the first and second stage revision in PJI has not yet been defined. T Winkler et al. conducted a prospective study wherein they defined a short interval as less than 4 weeks and a long interval as equal to or longer than 4 weeks. Their findings indicated that the outcomes of two-stage revision with a long interval were comparable to those of TSR with a short interval [ 21 ]. Similarly, in a meta-analysis performed by J Puetzler, compared with the long interval group, similar or even better infection control was observed for short interval [ 25 ]. However, existing literatures had a relatively small sample size, and the definitions of long interval and short interval lack consistency. In our study, the duration of interval in the case group was not significantly different from that of the control group, which was in line with previous studies. It was deduced that an interval less than 4 weeks could provide advantages treating PJI, such as reducing immobilization time and lowering economic costs. Apart from the rate of reinfection, inter-stage mortality is another important factor that we must take into consideration when determining the optimal time for reimplantation. Molly A Hartzler et al. reported a 3% mortality rate and a 28% complication rate between stages [ 39 ]. Keith R Berend also reported a 7% inter-stage mortality rate among patients with prosthetic hip joint infection [ 40 ]. It was inferred that a reduction of duration of interval was highly likely to reduce the rate of complications and mortality caused by long-term immobility [ 21 ]. However, due to concerns about infection control and inability to determine the exact time for reimplantation, some doctors avoided shortening duration of the interval and sometimes repeated the first-stage debridement.

Laboratory results, including serum CRP level, ESR and D-dimer level, serve as important reference indicators for surgeons to decide the timing to reimplantation. However, there is no standard in terms of laboratory results, with which surgeons can identify the patients who are at high risk of reinfection after TSR. Recently, Christian Klemt et al. conducted a study for exploring the role of CRP level and ESR prior to the second stage revision for knee in predicting optimal timing to reimplantation [ 41 ]. Results showed that patients with the elevated ESR and CRP level had a significantly higher reinfection rate than patients with normalized ESR and CRP, patients with elevated ESR and normalized CRP, and patients with normalized ESR and elevated CRP. These results indicated that elevation of both ESR and CRP were associated with a higher risk of reinfection compared with normalized either ESR or CRP. In our study, results showed that patients with diagnosis of reinfection after TSR had significantly higher median CRP level prior to the second stage revision compared with patients without reinfection (8.80 mg/L versus 2.36 mg/L, p  = 0.005), even though all patients’ CRP level were normalized, which were partially in line with the study of Christian Klemt et al. Therefore, patients with normalized CRP level prior to the second stage revision, which was defined with the present cut-off value, are still possibly at high risk of reinfection after TSR. However, another three studies exhibited conclusions that CRP, serum WBC count and ESR were not helpful to decide the timing of reimplantation and could not predict reinfection after TSR, which were contrary to ours [ 27 , 29 , 30 ]. Nevertheless, two of these three studies included both patients underwent TSR of hip and patients underwent TSR of knee [ 27 , 29 ]. While in the other study, there was no antibiotics holiday period for patients between the two stages, and thus CRP level and WBC count might not return to the state prior to PJI after six-week anti-infection therapy [ 30 ]. All the same, we should still keep in mind that when determining the timing to perform the reimplantation, we ought to consider other inflammatory indices, patients’ clinical signs and the course of antibiotics as well, rather than rely on a specific index. For patients with sinus tracts, during the antibiotics-free period, it is essential to actively monitor CRP levels and their trends. Besides, further research is needed to provide more proofs for the predictive power of CRP level on reinfection and define the new cut-off value for predicting reinfection.

Gram-positive cocci accounts for the majority of PJI with monomicrobial infections [ 2 ]. Likewise, our study also showed that gram-positive cocci were detected in 15 patients out of 22 patients who had positive cultures before the first-stage revision. However, positive culture rate in our study was only 58%, which was lower than other studies [ 42 ]. It was probably because samples for culturing were obtained from synovial fluid and synovium during the first-stage revision, before which systemic antibiotics had already been administered for a period. Prior studies indicated that culture-negative and culture-positive PJIs had a similar reinfection rate after TSR, which were different from our study [ 43 , 44 ]. In our study, results showed that the reinfection group had a higher percentage of positive cultures when compared with the no-reinfection group (100% versus 50%, p  = 0.030), indicating that positive culture during the first-stage revision was a risk factor of reinfection after TSR for prosthetic hip joint infection. We proposed that patients with negative cultures were more likely to achieve infection control due to their good immunity and the lower toxicity of the bacteria they might be infected with. Thus, these patients might have a lower reinfection rate. In addition, even though we did not detect any patients with polymicrobial infections in our study, it was reported by some authors that polymicrobial infections were associated with failure of TSR [ 45 , 46 ]. Moreover, among patients with positive cultures, three of six patients in the reinfection group were infected with Methicillin Sensitive Staphylococcus Aureus (MSSA) (50%), while in the no-reinfection group, there were only two of 16 patients infected with MSSA (25%). In line with our results, Curtis W Hartman et al. also reported a statistically significant association between infection with MSSA and reinfection ( P  = 0.046) [ 47 ]. As for post-operative antibiotic therapy, the combination of vancomycin and meropenem were administered intravenous for two weeks for culture-negative PJIs during the stay in the hospital. Discharged patients continued the combination of sulfamethoxazole and linezolid orally another four weeks. In our study, culture-negative patients had no reinfection during the follow up, thus we believe this regimen can treat almost all the microbial organisms except for tuberculosis and fungi.

Finally, there are some limitations in our study that should be taken into consideration when interpreting the results. First, this is a retrospective case-control study with inherent limitations. Second, due to a relatively small sample size, regression analysis could not be performed. Third, patients without complete medical records and patients who received the first-stage or the second-stage revision at other hospitals were excluded, which might lead to incomplete inclusion of the cases without reinfection after TSR. Therefore, in the future, we will try to conduct a multi-center, prospective study with larger sample sizes to further investigate these risk factors.

In conclusion, thiswe presented a case-control study showed that the presence of sinus tracts around the prosthetic hip joint prior to the first-stage revision could significantly increase risk of postoperative reinfection. Additionally, positive cultures of synovial fluid and synovium during the first stage revision and elevated CRP level prior to the second stage revision could also significantly increase the risk of reinfection after TSR for PJI of hip. Further studies with a larger sample size are required to confirm these findings and develop effective prevention.

Acknowledgements

Not applicable.

Abbreviations

Author contributions

All authors contributed to the study design. Material preparation, data collection and analysis were performed by Hongjun Xu, Songlin Li, Sen Liu. The first draft of the manuscript was written by Hongju Xu, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

This work was supported by the National High Level Hospital Clinical Research Funding (Grant number: 2022-PUMCH-B-001) and the CAMS Innovation Fund for Medical Sciences (CIFMS, 2022-I2M-C&T-B-034).

Data availability

Declarations.

Ethics approval was granted by the Ethics Committee of Peking Union Medical College Hospital (No. K5245). Written informed consents were obtained from patients who were literate. While for patients who were illiterate or could sign their names, verbal informed consents from the patients and written informed consents from the patients’ guardian were acquired. This study was performed in line with the principles of the Declaration of Helsinki.

The authors declare no competing interests.

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