Dynamic hip screws versus cephalocondylic intramedullary nails for unstable extracapsular hip fractures in 2021: A systematic review and meta-analysis of randomised trials

Background Extracapsular hip fractures comprise approximately half of all hip fractures and the incidence of hip fractures is exponentially increasing. Extramedullary fixation using a dynamic hip screw (DHS) has been the gold standard method of operative treatment for unstable extracapsular fractures, however, in recent years, intramedullary nails (IMN) have become a popular alternative. IMN versus DHS is continuously discussed and debated in literature. Therefore, the purpose of this systematic review and meta-analysis is to directly compare the peri- and post-operative outcomes of these two techniques to provide an up-to-date analysis of which method of fixation is superior. Methods The MEDLINE/PubMed, Embase and Web of Science Database were searched for eligible studies from 2008 to April 2022 that compared peri- and post-operational outcomes for patients undergoing IMN or DHS operations for fixation of unstable extracapsular hip fractures (PROSPERO registration ID:CRD42021228335). Primary outcomes included mortality rate and re-operation rate. Secondary outcomes included operation time, blood loss, transfusion requirement, complication, and failure of fixation rate. The risk of bias and quality of evidence were assessed using the Cochrane RoB 2.0 tool and GRADE analysis tool, respectively. Results Of the 6776 records identified, 22 studies involving 3151 patients were included in the final review. Our meta-analysis showed no significant differences between mortality rates (10 studies, OR 0.98; 95% CI 0.80 to 1.22, p = 0.88) or re-operation rates (10 studies, OR 1.03; 95% CI 0.64 to 1.64, p = 0.91) between the two procedures. There were also no significant differences found between complication rates (17 studies, OR 1.29; 95% CI 0.79 to 2.12, p = 0.31) and failure of fixation rates (14 studies, OR 1.32; 95% CI 0.74 to 2.38, p = 0.35). However, DHS operations had a significantly longer operation time (p < 0.0001) and blood loss (p < 0.00001) than IMN operations. Conclusion Overall, based on the outcomes assessed, this review has demonstrated that there is no significant difference in the post-operative outcomes for DHS vs IMN, however a significant difference exists in two of the intraoperative outcomes assessed in this review.


Introduction
Hip fractures are one of the most common injuries affecting patients >65 years and are associated with significant morbidity and mortality.The incidence of hip fractures increases with age and commonly present as fragility fractures that result from osteoporosis.
Due to an increasingly ageing population, the incidence of hip fractures is exponentially expanding and majorly impacting healthcare systems and patients.In 2019, 76,000 patients presented to a hospital in the UK with a hip fracture, an increase from the approximate 65,000 patients that presented in 2017. 1,2Hip fractures also account for 1.8 million hospital bed days per year and cost the NHS £1.1 billion in hospital costs annually, excluding the costs of social care. 3][6] Extracapsular hip fractures comprise approximately half of all hip fractures and are usually the result of low-energy mechanisms in elderly patients. 7,8The AO/OTA classification can be used to classify extracapsular hip fractures depending on the relationship of the fracture to the greater and lesser trochanters.Extracapsular hip fractures are classified by AO as Type 31-A and subdivided into groups A1, A2 and A3.Type A1 is a stable trochanteric fracture, type A2 is an unstable trochanteric fracture and type A3 is an unstable transtrochanteric fracture, which includes fractures at the level of the lesser trochanter and reverse oblique patterns. 9xtracapsular fractures are generally treated by surgical intervention.Most of the bone in this area is cancellous and highly vascularised in comparison to intracapsular hip fractures, resulting in a robust healing environment suitable for operations. 4,7For the past 40 years, the dynamic (sliding) hip screw (DHS) has been the gold standard method of operative treatment for extracapsular hip fractures. 10DHS consists of a lag screw passed into the femoral head which is then attached to a plate, to be secured on the side of the femur, allowing the femoral head component to move along one plane whilst enabling compression at the fracture site. 11In the last 20 years, intramedullary nails (IMNs) have become a popular method of fixation as an alternative to DHS, especially for those with unstable fracture patterns.A cephalocondylic IMN is inserted through the greater trochanter or piriform fossa of the femur and is secured by a screw that is passed up from the femoral neck into the femoral head. 12They may be biomechanically advantageous for unstable fractures by providing better load sharing. 10ntramedullary versus extramedullary fixation is still frequently and controversially discussed and debated in the literature.Older studies (1991-1999) demonstrated that the DHS appeared to be a superior implant to IMN due to lower complication rates and risk of femoral fracture, however, newer studies (2000-2005), utilising newer generations of IMN, demonstrated that IMN did not increase the risk of periprosthetic femoral fracture. 13The current NICE guidelines recommend DHS as the surgical treatment for A1 and A2 fractures and IMN for A3 fractures whereas the American Academy of Orthopaedic Surgeons (AAOS) guidelines recommend either DHS or IMN for stable fractures and IMN for unstable fractures. 14,15These guidelines however are still not supported by clinical studies as many recent meta-analyses have demonstrated no notable difference or advantage to choosing DHS in comparison to IMN. [16][17][18] The purpose of this systematic review is to evaluate more recent randomised controlled trials comparing IMN and DHS in adult patients for the stabilisation of extracapsular hip fractures from 2008 to 2022 to provide a more focused analysis of the outcomes using newer generations of IMN and DHS implants.This review will assess and evaluate the recent evidence for treating adult patients with unstable extracapsular hip fractures using either IMN or DHS to assess which procedure results in better peri-and post-operative outcomes for the patient.

Methods
The article search and selection for this review were carried out based on the standardised methodology recommended by the Cochrane Methods group for the systematic review of interventions and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria.

Search strategy
The protocol for this review was prospectively registered on PROS-PERO (registration ID CRD42021228335).MEDLINE/PubMed, Embase and Web of Science were searched for eligible studies.The search was limited to studies from 2008 to April 2022.Details of the search strategy have been provided (Appendix A).Two reviewers (SG and SR) performed the search and evaluated titles, abstracts then full-text articles to decide on eligible studies to include.The reference lists of the articles included were also searched for further eligible studies.The Cochrane Risk of Bias 2.0 Tool was used to guide the assessment of the studies identified from the literature search. 19For all eligible articles, SG and SR performed data extraction including demographics of participants, study characteristics, procedures and outcomes.Any disagreement was resolved via discussion and any dispute was settled by a consensus involving all authors.The data from eligible articles were inputted into a pre-defined spreadsheet that was reviewed by an additional author (APa).

Eligible studies
Only randomised/quasi-randomised studies comparing perioperational and post-operational outcomes for patients undergoing operations with cephalocondylic IMN in comparison with DHS for fixation of unstable extracapsular trochanteric hip fractures were included in this review.Duplicate studies, case reports, editorials, letters, and conference proceedings were excluded as per the pre-determined inclusion and exclusion criteria (Table 1).

Eligible participants
This systematic review included male or female skeletally mature patients with unstable extracapsular (intertrochanteric or subtrochanteric) hip fractures undergoing treatment with either cephalocondylic IMN or DHS for fixation in the primary setting and therefore excluded those who were undergoing revision surgery.

Eligible interventions and comparators
The eligible intervention included fixation by cephalocondylic IMN of any material and type for fixation of unstable extracapsular hip fractures.The comparator was the use of DHS for fixation of unstable extracapsular fractures of any type and material regardless of technique.

Outcome measures
The primary outcome measures were patient mortality and reoperation rates at final follow-up, measured as percentages.The secondary outcomes were failure of fixation rate, complication rate and surgical outcomes, such as mean operating time, blood loss and transfusion requirement.

Assessment of risk of bias
All randomised control trials included in this study were assessed for risk of bias via the Cochrane Risk of Bias 2.0 tool 19 and the quality of our effect estimate was analysed using the GRADE ranking system. 20

Data analysis
All quantitative data for patient mortality and re-operation rates at final follow-up that were available have been included and presented in a table demonstrating primary outcomes.All quantitative data for secondary outcomes including operating time, blood loss, transfusion requirement, complication rate and failure of fixation have been measured as either mean or true values and presented in a table.A quantitative meta-analysis has also been carried out to compare mortality, re-operation, complication, failure of fixation rates, operative time and blood loss between the intervention and comparator using the Review Manager (RevMan 5.4.1)software.A random effects model was used as no fixed effects were assumed.When applicable, mean difference and odds ratios were calculated with confidence intervals provided.Studies that had incomplete data or incomparable outcomes were excluded from the meta-analysis.A full discussion of possible explanations and conclusions from the meta-analysis and tabulated data have been explored in the discussion and conclusion sections.

Results
Following a systematic search, 7510 studies were identified using pre-defined criteria.After the removal of duplicates, 6650 studies remained.860 abstracts were screened, after which 43 full-text articles were assessed for eligibility, of which 22 studies were included in this review.In accordance with the PRISMA criteria, a flow diagram demonstrating the study selection procedure has been included (Fig. 1).The PRISMA checklist has also been included (Appendix B).

Study characteristics
The baseline characteristics of the included studies are recorded in Table 2.Only studies that compared fixation of unstable extracapsular hip fractures using DHS and IMN were included in this systematic review.8][39][40][41][42] Only one study utilised a single surgeon for all of the operations included in the study. 35The patient recruitment period ranged from 2006 to 2019, and all studies were published after 2008.A total of 3151 patients with a mean age of 74.5 (range 58-84) were included; the median number of male and female participants was 25 and 65 respectively.Overall, 1595 and 1556 patients underwent treatment with DHS and IMN, respectively.The types of IMN used included, but was not limited to, gamma nail, intramedullary hip screw and proximal femoral nail.Patients included had 31-A1, 31-A2 or 31-A3 fractures, as classified by the AO/OTA classification.The median follow-up duration was 12 months (range 6-18 months).

Primary outcomes
The individual results for the primary outcomes are shown in Table 3.The primary outcomes were mortality rate and reoperation rate for fixation failure at final follow-up.33][34][35]37,40,41 None of these studies reported any statistically significant difference in mortality rates at final follow-up between patients that were treated with DHS versus those treated with IMN.

Secondary outcomes
The individual results for secondary outcomes are shown in Table 4.

Quality assessment
The studies involved in this review were all assessed using the Cochrane Risk of Bias 2.0 Tool and deemed to have some level of bias     5).A GRADE analysis was done for the studies included in the meta-analysis.Failure of fixation revealed a very low overall GRADE rating whereas, re-operation for failure of fixation and complication rate revealed a low rating and mortality rate, a moderate rating (Table 6).

Summary of findings
This systematic review and meta-analysis has been conducted to provide an up-to-date review to determine which procedure, IMN or DHS, results in better peri-operative and post-operative outcomes.In summary, based on the meta-analysis performed, there was no statistically significant difference in mortality or reoperation rates for either type of operation at final follow-up.There was also no statistically significant difference in complication rate for either procedure as per the meta-analysis.However, the majority of studies included reported that DHS procedures led to significantly higher blood loss and longer operation time than IMN procedures; this was statistically significant in the meta-analysis for these two intra-operative outcomes.

Previous systematic reviews
At the time of writing, this review is the largest systematic review with a meta-analysis that compares mortality and re-operation rates alongside other further adverse outcomes between DHS and IMN procedures.In 2017, a review investigating nail versus plate fixation was published by Parker et al., 43 which primarily looked at complications relating to fracture health.Although this review concluded that there was no difference in complication rates for either DHS or IMN procedures, this review only included type A3 fractures and only involved a total of 9 studies.A more recent review published by Lewis et al. 44 in 2022 compared intramedullary versus extramedullary fixation for extracapsular fractures.Contrary to our review, their primary outcomes were predominantly function-related including: performance of activities of daily living, functional status and health-related quality of life.Although this review involved 76 studies, the review reported that over half of the studies were conducted prior to 2010 and stated that the authors "could not easily judge whether care pathways in these older studies were comparable to current standard of care". 44Moreover, a similar 2022 review also assessed post-operative outcomes including complication rate, non-union, infection or mortality rates between DHS and IMN for AO/OTA subtypes: A1, A2 and A3.The authors investigated each subtype separately and reported difficulty in obtaining data for each one and therefore could not complete a meta-analysis. 18Our review therefore adds to the existing literature by providing an up-to-date review that directly compares DHS and IMN procedures for all of A1, A2 and A3 extracapsular fractures collectively and specifically addresses peri-operative as well as post-operative outcomes.

Primary outcomes
In this review, the studies included reported various peri-and postoperative outcomes.5]33,35,40,43 Our review found no difference in mortality rate at final follow-up between DHS and IMN procedures.This is in keeping with previous reviews by Wessels et al. 18 and Zhang et al., 45 that also found no difference in mortality rate when comparing DHS to IMN.It has been suggested both procedures could result in a mortality rate of up to 10% in the first year post-procedure, however this could be attributed to the predominantly elderly age group being treated and their existing medical comorbidities. 36Our review also demonstrated no significant difference in reoperation rate for fixation failure for either procedure.Alternatively, one study that investigated 17,341 patients demonstrated a lower reoperation rate for IMN at 1 and 3 years in comparison to DHS for unstable femoral fractures. 46However, this study investigated reoperations for various other reasons such as implant-related infection, peri-implant fracture, mechanical complications and pain, as opposed to failure of fixation only.

Secondary outcomes
In this review, no single study reported all secondary outcomes and the number of secondary outcomes reported by each study ranged from 0 to 5, meaning that there was marked heterogeneity in the number of secondary outcomes reported.Only a few studies reported the transfusion requirement, therefore it was not possible to carry out a metaanalysis for this outcome.Meta-analysis was completed for the remaining secondary outcomes and although no significant difference was found in complication rate or failure of fixation rate, a significant difference was found in both operation time and blood loss.
The meta-analysis results demonstrated that the operation time was significantly longer for DHS operations and the blood loss was also greater, in comparison to IMN operations.This finding is in keeping with the literature.A previous meta-analysis comparing the same two interventions involving 3097 patients by Hao et al. identified that the operation time was significantly longer and blood loss significantly greater in DHS operations in comparison to IMN. 47 Another previous meta-analysis recommends the use of IMN for the treatment of unstable intertrochanteric fractures based on the fact that it results in reduced blood loss. 48There is speculation to suggest that DHS operations could result in more blood loss and higher infection rate given that they have a longer operative time. 49he meta-analysis of the 17 studies that reported complication rate revealed that there was no significant difference in complication rates between either procedure.In keeping with the literature, one study followed approximately 5700 patients over 7 years following DHS or IMN procedures and noted that within 30 days after surgery, the complication rates was exactly 16% for both groups (p = 0.98). 50imilarly, a further meta-analysis showed no significant differences in implant-related post-operative complications such as femoral shaft fracture, non-union, breakage of implant and migration of screw between DHS or IMN. 51Our review showed no difference in failure of fixation for either procedure.Although failed fixations are rarely reported, a previous study has provided data suggesting that for some unstable fracture patterns including high comminuted fractures or reverse oblique fractures, DHS may be more likely to fail. 52Further comparison for specific unstable fracture types would be required before this can be confirmed, as well as investigating complication and failure of fixation over longer follow-up periods.
Even though DHS and IMN procedures provide similar postoperative outcomes such as mortality, complication, and failure of fixation rate, the results from our review have demonstrated that the DHS procedure results in a proportionally greater blood loss and longer operating time in comparison to IMN.This is suggesting that IMN could arguably be a safer treatment option from the intraoperative aspect, however, DHS remains the gold standard operation in the UK.A previous study in the US demonstrated that along with fixation failure rate, implant cost were the most important factors in determining implant choice for unstable intertrochanteric fractures. 53Another study conducted in India reported that the cost of an IMN is 7-8 times the cost of DHS and therefore heavily influencing the decision for method of treatment. 54Based on this data, in order to justify the increased use of IMN in the UK, a comparison of clinical and cost effectiveness between the two outcomes may be required.

Strengths and limitations
The strengths of this review include a prospective registration of the study protocol as well as an up-to-date literature search.This review also includes a meta-analysis to compare the primary and some of the secondary outcomes.However, the limitations of this study should be considered.Firstly, there have been previous studies 43,44 that have suggested that variations of IMN could have different success rates in comparison to DHS, however this was not investigated further in our review.Secondly, this review did not investigate the different surgical techniques for DHS and IMN to assess whether that had any impact on the results.Furthermore, this review also included older studies, from 2008-2010, 21,22,[37][38][39][40] which perhaps utilised older techniques and older models of nails and screws, thereby potentially affecting the peri-and post-operative outcomes.Finally, when assessing the risk of bias using the Cochrane Risk of Bias tool, seven studies were deemed to have an overall 'high risk' of bias of and the remaining studies were deemed to have 'some concerns.'

Conclusion
Overall, based on the studies that were included and outcomes that were assessed, this systematic review has found that there is a difference in two intraoperative outcomes: operation time and blood loss in favour of IMN.However, there is no significant difference in the post-operative outcomes between IMN and DHS.More high-quality studies could be conducted to compare the clinical and cost effectiveness between these two techniques.Additionally, studies could also compare the use of these two techniques for different types of unstable fractures.

Fig. 7 .
Fig. 7. Meta-analysis of failure of fixation rates between DHS and IMN.

Table 1
Inclusion and exclusion criteria.

Table 2
Patient characteristics.

Table 3
Primary outcomes (mortality rate, re-operation rate due to failure of fixation).

Table 4
Secondary outcomes (operation time, blood loss and transfusion requirement, complication rate, failure of fixation rate). (Table

Table 5
Risk of bias for randomised comparative studies using the Cochrane RoB 2.0 tool.

Table 6
Quality of evidence of each outcome using the GRADE analysis.