What is the best method of fixation for minimally displaced subcapital neck of femur fractures? A systematic review

Abstract

Background.

Femoral neck fractures are a common cause of morbidity and mortality in the community. Minimally displaced subcapital necks of femoral fractures are usually managed with internal fixation, although there is debate as to which method is superior. This systematic review aimed to compare the outcomes of different fixation methods in the management of this common fracture.

Methods.

This systematic review was conducted in accordance with PRISMA statement guidelines. The databases searched were MEDLINE (Ovid), Cochrane Central Register of Controlled Trials, and EMBASE (Ovid). The study quality and risk of bias were assessed using the Newcastle-Ottawa Quality Assessment Scale, and relevant data were extracted and synthesised.

Results.

Nine articles met the inclusion criteria. A total of 819 patients were included in this study. Eight of the nine studies were case series, and one was a randomised control trial. The mean risk of bias was 7.4/9 for non-randomised articles. The fixation methods used in the included studies were dynamic hip screw (DHS), cannulated screws, Smith-Peterson nail, hooknail, Moore's pins, and Knowle's pins. DHS was found to be a superior method of fixation and was supported by a clinical trial. It has high rates of union (99 %), low rates of avascular necrosis (<1 %), and low rates of fixation failure (<1 %).

Conclusions.

Based on the available data, DHS appears to be the superior method of fixation for the minimally displaced subcapital neck of femoral fractures. Given the general low level of evidence currently available, additional clinical trials are needed in this area.

1. Background

Hip fractures, specifically fractures in the neck of the femur (NOF), pose a significant risk of injury, morbidity, and mortality among elderly individuals.¹ Despite advances in the treatment of osteoporosis resulting in decreased incidences of femoral neck fractures, the absolute number is increasing as our population ages.² This is attributed to increased risk of fall-related injuries (which are subsequently influenced by social and lifestyle changes), more frequent medication use, less active lifestyles, poorer general mobility, and reduced bone and muscle strength.³

Among the elderly, subcapital fractures of the neck of the femur (NOF) are frequently observed. These fractures involve the area where the femoral head and neck meet, and are associated with a notable risk of non-union and delayed segmental collapse of the femoral head.⁴ Displaced subcapital NOF fractures have a higher likelihood of disrupting the retinacular vessels, which are crucial for the blood supply to the femoral head. The femoral head is supplied by three groups of vessels: superior, inferior, and anterior retinacular arteries.⁵ The severity of vascular injury is directly related to the displacement of the fracture, which subsequently relates to the risk of femoral head osteonecrosis,⁵ and thus, displaced fractures are typically treated with hemiarthroplasty or total hip arthroplasty.^6,7

At present, available treatment options for these fractures encompass the utilisation of hip compression screws, percutaneous pinning techniques, placement of two or three parallel screws, or consideration of arthroplasty procedures. These methods are commonly employed to address subcapital neck fractures of the femur in the elderly population and aim to provide stabilisation and promote proper healing.^8,9 However, there remains ambiguity regarding the superior method of operative fixation. Whilst there is data comparing operative interventions for intracapsular NOF fractures, there is a paucity of data specifically investigating minimally displaced subcapital NOF fractures.10, 11, 12, 13 Clear guidance on the surgical management of subcapital NOF fractures is needed, given the high incidence of non-union and late segmental collapse.¹⁴

The objective of this systematic review was to comprehensively search and analyse the available literature from multiple databases from inception, to determine the optimal fixation method for minimally displaced subcapital fractures of the neck of the femur (NOF). The review specifically aimed to compare different fixation methods in terms of their effectiveness in achieving union, preventing avascular necrosis, reducing fixation failure, and improving patient-reported outcome measures. The findings of this review can strongly inform surgeons about the optimal fixation strategy for this specific fracture pattern and contribute to the ongoing advancement of treatment options in this field.

2. Methods

The focus of this review is to analyse management options for minimally displaced subcapital NOF fractures classified as Garden types I and II.¹⁵ Treatment decisions and prognostic considerations for femoral neck fractures are influenced by the Garden classification, which evaluates the degree of displacement and the potential impact on the vascular supply to the femoral head. This classification system plays a pivotal role in guiding appropriate treatment interventions and predicting the likely outcomes for patients with these fractures.¹⁶

This review was registered with PROSPERO on the November 11, 2020 (PROSPERO 2020 CRD42020209112), and was conducted in accordance with the PRISMA statement guidelines (Fig. 1).¹⁷

Fig. 1.

Prisma flow diagram.

2.1. Search strategy and identification of studies

The following databases were searched on 20th July 20, 2021, MEDLINE (Ovid), Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE (Ovid). The databases were searched from their inception. An experienced librarian assisted with the search strategy and design, and the final search was completed using the following Medical Subject Headings (MeSH) terms: subcapital, intracapsular, hip fracture, hip fractures, femoral neck fracture, femoral neck fractures, femur fracture, femur fractures, and femoral neck (syntax attached as Appendix 1).

Screening procedures were carried out employing Covidence systematic review software, developed by Veritas Health Innovation in Melbourne, Australia. To manage the articles during the full-text review, EndNote EX9 software was utilised. Two independent reviewers (JK and TS) conducted the initial screening of articles based on their titles and abstracts. Articles which did not meet the inclusion criteria or had no full text available were excluded. In the case of discrepancies, a third investigator (JQ) was involved to resolve any differences, however, the third reviewer was not required for the screening arm.

Full-text versions of the selected studies were obtained, and each article underwent a comprehensive evaluation for eligibility during the full-text review stage.

A manual review of the reference lists of the full text articles was also completed for additional citations. The manual review followed the same protocol as the screening tool, whereby articles were included by their relevance, meeting inclusion criteria, having full text reviews and being in English.

2.2. Inclusion criteria

The inclusion and exclusion criteria listed appear to be reasonable and valid for the specific objectives of the systematic review. They are designed to ensure that relevant studies with minimally displaced subcapital NOF fractures and operative interventions are included while avoiding bias and focusing on the research question.

• 1.Participants with a minimally displaced subcapital NOF fracture: This criterion specifies the target population under investigation, ensuring that only studies focusing on minimally displaced fractures are included, providing a specific and defined study group.
• 2.Operative intervention with any method of fixation: This criterion ensures that studies exploring various operative fixation methods for minimally displaced subcapital NOF fractures are considered, thereby addressing the review's primary objective.
• 3.Outcomes reporting at least one of the following assessments were included: rates of union or non-union, failure of fixation, and/or functional outcome score: This criterion identifies the outcome measures of interest for the systematic review, facilitating the evaluation of the effectiveness of different fixation methods based on their ability to achieve union, prevent non-union, avoid fixation failure, and improve functional outcomes.
• 4.Studies published in peer-reviewed journals and available in English language were included: This criterion helps maintain the quality and reliability of the included studies, as peer-reviewed publications typically undergo rigorous scrutiny. Limiting the search to English language studies is a common practice in systematic reviews due to language constraints and the resources available to the reviewers.

2.3. Exclusion criteria

To avoid bias related to diagnosis, the following studies were excluded.

• 1.Studies which did not specify how the subcapital NOF fracture was diagnosed: This criterion ensures that studies without clear diagnostic criteria for subcapital NOF fractures are excluded, preventing potential misclassification or heterogeneity in the study population.
• 2.Studies grouped intracapsular NOF fractures generally and not specifically subcapital NOF fractures: This criterion helps avoid ambiguity and ensures that the systematic review focuses solely on minimally displaced subcapital NOF fractures, which have distinct characteristics and outcomes compared to other intracapsular fractures.
• 3.Studies not written in English: Excluding non-English studies may help overcome language barriers in data extraction and analysis, though it's essential to acknowledge the potential for language bias.
• 4.Case reports: Excluding case reports is reasonable as they typically describe individual cases and may not provide sufficient evidence for the systematic review's objectives.
• 5.Active/incomplete studies: Excluding active or incomplete studies helps ensure that only fully published and final reports are included, avoiding the potential inclusion of preliminary or interim findings that may change with further data collection or analysis.

2.4. Methodological quality assessment

To evaluate the risk of bias, and methodology in the selected articles, two reviewers (JK and TS) utilised the Newcastle-Ottawa Scale (NOS) for assessing the quality of non-randomised studies in meta-analyses, and the Risk of Bias 2 tool for RCT's.

The NOS assesses three main aspects of study: selection of study groups, comparability of the groups, and the ascertainment of exposure or outcome of interest. Each aspect is broken down into several items for evaluation.

• •Selection of study groups: Assessing whether the exposed and non-exposed cohorts are representative and appropriately selected with confirmed exposure and absence of the outcome at the study's start.
• •Comparability of the groups: Evaluating whether the study adequately controlled for confounding factors and had sufficient follow-up time for outcome detection.
• •Ascertainment of the outcome of interest: Assessing the methods used to determine the outcome and ensuring an adequate follow-up period.

Each item is scored on a scale of stars (often from 0 to 9 stars), with higher scores indicating higher methodological quality and lower risk of bias. Based on the scores obtained, the studies were categorised into three levels of quality: low quality (0–3), medium quality (4–6), and high quality (7–9). These quality levels were determined to reflect the rigor and reliability of the included studies. The results of the quality assessment, along with corresponding scores, are presented in Table 3, providing a comprehensive overview of the quality distribution among the selected studies. The NOS, whilst in its 1st version, being under development, and not yet published in peer-reviewed journals, was utilised for ease of use and applicability for both cohort and case-control studies.¹⁸

Table 3.

Methodological quality assessment for non-randomised papers (Newcastle Ottawa Scale).

	Selection				Comparability	Outcome			Total number of stars
Included Study	Representativeness of the exposed cohort	Selection of the non-exposed	Ascertainment of incident	Outcome of interest absent at start of study	Comparability	Assessment of outcome	Length of follow-up	Adequacy of follow-up
Cobb (23)	A*	C	A*	A*	*	B*	A*	B*	7
Heyse-Moore (20)	A*	C	A*	A*	*	B*	A*	A*	7
Chiu (26)	B*	C	A*	A*	*	B*	A*	A*	7
Barnes (4)	A*	A*	A*	A*	**	B*	A*	A*	9
Higgins (21)	A*	C	A*	A*	*	B*	A*	B*	7
Doran (24)	B*	C	A*	A*	*	B*	A*	B*	7
Ackroyd (25)	B*	C	A*	A*	*	B*	A*	B*	7
Kang (22)	B*	C	A*	A*	**	B*	A*	A*	8

The RCT that was included in the final review was left out of the NOS assessment. To assess risk of bias, the 2019 version of the Risk of Bias (RoB) 2 tool for randomised control trails¹⁹ was utilised. This includes assessing five domains including: randomisation process, deviations from the intended interventions, missing outcome data, measurement of the outcome, and selection of the report result. The rational for using this tool was that its ease of use, constant updates, and it being the most commonly used tool for RCT's.¹⁹

2.5. Data extraction and analysis

Two reviewers independently extracted information on the study design, country of origin, fixation method, follow-up duration, and outcomes. The outcomes of interest in this systematic review included the frequency of non-union, avascular necrosis (AVN), fixation failure, and patient outcome measures. The extracted data was compiled and presented in Table 1. Descriptive analysis was conducted on the data, as the studies included exhibited significant heterogeneity, precluding a meta-analysis.

Table 1.

Included study fixation methods.

Article/Country/Year	DHS	Cannulated screws	Smith Petersen Nail	Knowle's Pins	Moore's Pins	Hook Pin	Non-operative	Total
Cobb, UK, 1986 (23)	0	38	0	0	0	0	0	38
Watson, Australia, 2012 (2)	22	22	0	0	0	0	0	44
Heyse-Moore, UK, 1996 (20)	37	0	0	0	0	0	0	37
Chiu, Taiwan, 1996 (26)	0	0	0	305	0	0	0	305
Barnes, UK, 1976 (4)	45	15	117	0	0	0	18	195
Higgins, UK, 2004 (21)	0	96	0	0	0	0	0	96
Doran, UK, 1989 (24)	0	0	0	0	0	46	0	46
Ackroyd, UK, 1973 (25)	0	0	0	0	9	0	0	9
Kang, Korea, 2016 (22)	0	49	0	0	0	0	0	49
Total	104	220	117	305	9	46	18	819

Abbreviations: DHS dynamic hip screw.

3. Results

The initial search of the literature identified a total of 250 articles, and an additional 10 articles were obtained through manual searches of reference lists from the full text review list. After removing duplicates, 90 articles were excluded, leaving 160 unique articles for further evaluation. During the abstract/title review, 140 articles were excluded based on their relevance to the research question. The excluded articles were due to several reasons including comparison between fixation and replacement management options, no full text available, text not in English, primary and secondary outcomes not in keeping with the research question, not specifying subcapital neck of femur fracture or having too general an application of the Garden Classification (i.e., using it generally for intracapsular neck of femur fractures as opposed to solely subcapital).

The remaining 20 articles underwent full-text screening, resulting in the exclusion of 11 studies that did not meet the inclusion criteria. To gather additional information, the first authors/main contacts of the excluded articles were contacted. Reasons for this mainly revolved around specifying their use of the Garden Classification (broadly or for subcapital neck of femur fractures). Unfortunately, there were no responses from any of these authors.

Ultimately, nine articles were identified that met the specified inclusion criteria and were included for analysis. These selected articles, along with their relevant details, are presented in Table 1, providing a comprehensive overview of the studies that were considered for the systematic review.

3.1. Summaries of included studies

Watson et al² conducted a randomised control trail to compare the effectiveness of dynamic hip screw (DHS) fixation and cannulated screw fixation in treating femoral neck fractures. The trial findings demonstrated that the DHS cases exhibited higher rates of union and lower rates of failure compared to the cannulated screw cohort. Interestingly, patient-reported outcomes, particularly in terms of function and quality of life, were more favourable in the group treated with cannulated screws. However, it is important to emphasise that the observed difference in patient-reported outcomes did not reach statistical significance.

Barnes et al.⁴ followed 295 cases with multiple fixation methods, including nonoperative management. Overall, 220 patients were united by 12 months, including all patients treated with DHS or cannulated screw fixation. Of note, all patients were managed non-operatively for fracture union. A total of 34 patients had AVN.

Heyse-Moore et al.²⁰ examined 37 patients treated with a one-hole DHS construct. All patients achieved union 6 months postoperatively.

Higgins et al²¹ reviewed 96 cases managed with cannulated screws, of which 75 patients achieved union. 21 patients required revision surgery (3 due to non-union, 6 due to fixation failure, and 12 due to AVN).

Kang et al.²² investigated 49 patients who were treated with cannulated screws. 47 patients who went onto union, two had AVN (post-union) and two patients had fixation failure.

Cobb et al.²³ examined 38 patients who underwent cannulated screw fixation. Non-union occurred in three patients, AVN occurred in three patients, and fixation failure occurred in 10 patients.

Doran et al²⁴ reviewed 46 patients who were managed with hook-pin fixation, of which 40 achieved union, 4 developed AVN, and 2 had fixation failure.

Ackroyd et al.²⁵ assessed nine patients treated with Moore's pins. All the patients achieved union.

Chiu et al.²⁶ assessed 305 patients who were treated with percutaneous needle pins. 282 cases went onto union, nine experienced fixation failure, and 22 developed AVN.

Historical methods of fixation included in this study demonstrated a combined union rate of 93.5 % and a low rate of non-union, AVN, or fixation failure. This highlights the effectiveness of internal fixation (and even nonoperative intervention) in effectively managing minimally displaced subcapital NOF fractures.

3.2. Study characteristics

Six studies were prospective case series, four of which were from the United Kingdom (UK),^4,20,23,25 one from Taiwan,²⁶ and one from South Korea.²² Two studies were retrospective case series, both from the UK.^21,24 One study was a randomised controlled trial (RCT) from Australia.² Collectively, the data collected was from 1978 to 2010.

3.3. Participant characteristics

A total of 819 participants were enrolled in this review, with 25 % being male and 75 % being female. The age range of the participants spanned from 16 to 95 years, however, only six out of the nine articles included age ranges, so a mean was not calculable.

Among the 819 patients, the distribution of different management approaches was as follows: 104 patients underwent DHS management, 220 patients received cancellous screws, 305 patients were treated with Knowles' pins, 117 patients underwent Smith-Peterson nail fixation, 9 patients received Moore's pins, 46 patients had hook pins, and 18 patients did not undergo operative management. The detailed breakdown of the participants according to their management approach is provided in Table 1.

3.4. Methodological quality assessment

A summary of the risk of bias scores is shown in Table 3. The average rating for each study was 7.4/9 stars (ranging from 7 to 9, 9 being the best) with Barnes et al. rating the highest quality. The RCT, Watson et al. was assessed using the Risk of Bias 2 tool for randomised control trails and was found to have some concerns. This was with respect to the following domains: deviations from intended interventions and measurement of outcome (Table 4).

Table 4.

Methodological quality assessment for randomised controlled trails (RoB 2).

Included Study	D1 – Randomisation Process	D2 – Deviations from Intended Interventions	D3 – Missing Outcome Data	D4 – Measurement of the Outcome	D5 – Selection of the Reported Result	Overall
Watson (2)

4. Outcomes by fixation method

The attainment of union was nearly universal when dynamic hip screw (DHS) fixation was employed, with a remarkable success rate of 99 %. In contrast, a lower percentage of patients treated with cannulated screws achieved union, with a rate of 87 %. Historical methods of fixation have demonstrated variable rates of union, all surpassing the threshold of 80 %.

The incidence of avascular necrosis (AVN) was minimal in cases treated with DHS fixation, accounting for less than 1 % of the patients. Conversely, both cannulated screws and Knowles' pin fixation exhibited an approaching 7 % incidence of AVN.

Fixation failure was infrequent, occurring in less than 1 % of cases treated with DHS fixation, 5 % of cases with cannulated screw fixation, and approximately 3 % of cases treated with historical fixation methods.

Overall, of the contemporary methods of fixation, DHS fixation was found to have a union rate (99 %), failure fixation rate (<1 % pre-union) and AVN (<1 %). Cancellous screw fixation showed an 87 % union rate, a 7.7 % AVN rate (6.8 % pre-union, 0.9 % post-union), and an 8.6 % fixation failure rate (3.6 % pre-union, 5 % post-union) (Table 2).

Table 2.

Complications following fixation for subcapital neck of femur fracture.

Complication	Type of fixation (total)
	DHS (104)	Cannulated screws (220)	Smith Petersen Nail (117)	Knowle's Pins (305)	Moore's Pins (9)	Hook Pin (46)	Non-operative (18)
Union	103 (99 %)	192 (87 %)	114 (97.4 %)	282 (92.4 %)	9 (100 %)	40 (87 %)	18 (100 %)
AVN	1 (post-union)	2 (post-union) 15 (pre-union)	0	22 (post-union)	0	4 (pre-union)	0
Fixation failure	1 (pre-union)	11 (post-union) 8 (pre-union)	3	9 (pre-union)	0	2 (pre-union)	0
Non-union	1 (resulting in fixation failure)	5	0	14	0	0	0

Values are n (%).

Abbreviations: AVN avascular necrosis.

5. Patient reported outcome measures/functional outcome

Two studies reported functional outcomes.^2,26

Chiu et al. is a prospective case series which assessed 305 patients who were treated with percutaneous needle pins (Knowle's pins). 282 cases went onto union, nine experienced fixation failure, and 22 developed AVN. The study demonstrated 93.2 % ‘good’ functional outcome following fracture union, 5.3 % ‘acceptable results,’ and 1.5 % ‘poor results’.²⁶

Watson et al.² conducted an RCT to compare the effectiveness of DHS fixation and cannulated screw fixation in treating femoral neck fractures which demonstrated that the DHS cases exhibited higher rates of union and lower rates of failure compared to the cannulated screw cohort. For patient reported outcomes they compared DHS and cannulated screws using the Harris hip and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Harris Hip scores to assess functional outcomes. Both scores were higher for cannulated screw patients, but the difference was not statistically significant. Similarly, quality of life assessment using the Short Form-12 showed better results for cannulated screw fixation, but the difference was not statistically significant.

6. Discussion

When it comes to managing surgical pathology in the elderly, several factors need to be considered, including the anticipated risk, outcomes, and the economic and social costs associated with the chosen approach.²⁶ While non-operative interventions can avoid surgical risks, they often require extended immobilisation, patient cooperation, and endurance, leading to delayed functional recovery and a higher likelihood of perioperative medical complications.^26,27 Consequently, nonoperative management is not commonly practiced in modern orthopaedic care. Surgical fixation, on the other hand, enables early mobilisation, rapid functional recovery, and reduced perioperative medical complications, albeit with inherent surgical risks.^26,27 Although the orthopaedic community continues to debate the choice of fixation strategy, a comprehensive review of the available literature suggests that optimal fixation involves utilising a dynamic hip screw. This approach offers a high union rate, low incidence of avascular necrosis (AVN), and minimal implant failure.

Comparing fixation failure rates in this review, we found an almost 8-fold greater risk in patients treated with cancellous screws than in those treated with DHS. It has been theorised that poorer outcomes in patients with cancellous screw fixation are due to insufficient mechanical stability.²⁸ DHS provides angular stability, rotational stability, a stiffer construct, and controlled compression of the fracture fragments compared to cancellous screw fixation. The use of DHS also demonstrates a reduction in the occurrence of screw penetration ^{29,30 31}. Blair et al. completed a biomechanical study comparing DHS and cannulated screws and concluded that cancellous screws had a lower axial load to failure than DHS patients.²⁹ A similar conclusion was reached by Baitner et al. who showed that specimens stabilised using a DHS showed less inferior femoral head displacement, less shearing displacement at the osteotomy site, and a much greater load to failure than those stabilised with cannulated screws.³⁰

There was approximately an 8-fold greater rate of AVN was approximately eight-fold higher in patients treated with cancellous screws than in those treated with DHS. Han et al.³¹ found a significant association between Garden type and the occurrence of AVN in femoral neck fractures. They found that a displaced femoral neck fracture is a well-known risk factor for AVN, whereas in undisplaced femoral neck fractures, the posterior retinaculum is likely intact, thereby maintaining perfusion of the femoral head via the retinacular vessels.^32,33 In addition, no increased risk of AVN was found with longer time to surgery.³³ This is also supported by Razik et al. who similarly showed no significant pattern between increasing time to fixation and AVN rate, suggesting that it was not a valid predictor of AVN following internal fixation.³⁴ Thus, the two main determinants of AVN in patients with intracapsular femoral neck fixation are initial displacement and quality of reduction.

Therefore, when considering optimal management strategies for undisplaced subcapital NOF fractures, decisions should be driven by the displacement and strength of the fixation constructs. The improved biomechanical stability and rigidity of the DHS construct is likely the main difference, providing superior outcomes over cannulated screws.

7. Limitations

This review should be considered in light of some limitations. First, observer errors in identifying and diagnosing Garden I/II subcapital neck femur fractures could affect the number of truly undisplaced versus displaced subcapital NOF fractures included in the studies. This is consequential given that the impact on displacement is a risk factor for failure.^35,36 Second, there was little focus on functional outcomes, which are important indicators for the success of surgical intervention. This would have provided a complete and more rounded view of the fixation method outcomes. Third, the quality of studies is an important limitation for this review, as all studies were case series, except for one RCT. Additionally, only two of the nine studies were comparative studies. Fourthly, human error in data extraction process is possibility and may have an impact on completeness of data. Finally, some studies included patients with both nondisplaced and displaced fractures, which made it difficult to isolate data regarding nondisplaced fractures. A strictly designed and adequately powered RCT specifically investigating the Garden I/II subcapital neck of femoral fractures in the future is essential.

The strengths of this review include the robust methodology for study selection, adherence to validated and well-recognised measurement tools, and consistent outcome differences between methods of fixation. The assessment of historical fixation methods provides an interesting perspective and a clear benchmark for comparing current fixation strategies.

8. Conclusion

In conclusion, the findings of this systematic review provide compelling evidence supporting the superiority of dynamic hip screw (DHS) fixation in the management of undisplaced subcapital fractures of the neck of the femur (NOF). DHS fixation consistently yields favourable outcomes, including high rates of union, low incidence of avascular necrosis (AVN), and minimal fixation failure.

However, it is important to note that the current literature is limited, with only one randomised controlled trial (RCT) identified. Despite this limitation, the results of the available studies should instil confidence among surgeons in employing DHS fixation as the preferred approach for undisplaced subcapital NOF fractures in the majority of patients.

The findings of this review also provide a strong rationale for conducting a high-powered RCT to directly compare DHS and cannulated screw fixation in the management of minimally displaced subcapital fractures of the femoral neck. Such a study would further inform surgeons about the optimal fixation strategy for this specific fracture pattern and contribute to the ongoing advancement of treatment options in this field.

Declarationof AI and AI assisted teachnologies in the writing process

During the preparation of this work the author used Chat GPT (AI) to improve language and readability. After using this tool/service, the author reviewed and edited the content as needed and takes full responsibility for the content of the publication.

Declaration of competing interest

There are no acknowledgements, conflicts of interest and this research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors by any of the authors.

Appendix 1. Example of search strategy

• 1Femoral Neck Fractures/(9477)
• 2((femur or femoral) adj2 neck adj2 fractur*). tw. (7263)
• 3or/1–2 (11,999)
• 4Fracture Fixation/(19,232)
• 5exp Internal Fixators/(60,439)
• 6Orthopaedic Fixation Devices/(5066)
• 7(fracture adj2 fixation). tw. (4554)
• 8or/4–7 (82,391)
• 93 and 8 (2628)
• 10((minimal × adj2 displac*) or subcapital). tw. (1819)
• 119 and 10 (123)