Femoral neck fractures account for 3.6% of all fractures and 53% of hip fractures (1). With population aging, the incidence of hip fractures in older adults is projected to rise significantly (2). By 2050, the age-standardized incidence rate is expected to reach 1,055.30 cases per 100,000 person-years, imposing substantial socioeconomic and healthcare system burdens (3, 4). Moreover, femoral neck fractures in the elderly are predominantly osteoporotic fragility fractures, where intrinsically compromised bone quality and abnormal bone metabolism substantially increase the complexity of internal fixation and present an ongoing challenge for clinical decision-making (5).

Current surgical treatments for femoral neck fractures primarily involve internal fixation and hip arthroplasty (6). Among internal fixation methods, cannulated compression screws (CCS) and dynamic hip screws (DHS) are commonly used devices (7). The established CCS technique employs three screws arranged in an inverted triangular configuration, offering advantages such as minimal invasiveness, fracture compression, and rotational stability (8). This approach is particularly suitable for non-displaced fractures in elderly patients (9). However, CCS demonstrates limited shear resistance and provides only static compression, which may lead to micromotion at the fracture site during weight-bearing (10). This can hinder healing and increase risks of complications, such as screw cut-out and fixation failure. In contrast, DHS provides angular stability with enhanced lateral cortical support (11, 12). Its sliding compression mechanism promotes fracture healing, but the bulky design requires more extensive surgical exposure (13, 14). Consequently, the use of DHS may be restricted in patients with compromised overall health.

The femoral neck system (FNS; DePuy Synthes, Zuchwil, Switzerland), introduced in 2017, was designed to optimize minimally invasive techniques and enhance biomechanical stability (15, 16). The biomechanical study by Stoffel et al. demonstrated that the stability of FNS is superior to CCS and comparable to DHS (17). However, a clinical consensus is lacking regarding the comparative safety and efficacy of these three internal fixation techniques. Existing research remains confined to pairwise comparisons with limited sample sizes, resulting in reduced statistical power and imprecise effect estimates (18–21). To address this evidence gap, we conducted the first network meta-analysis integrating both direct and indirect evidence across all three fixation methods. This approach allows simultaneous comparison among multiple interventions, overcoming the limitations of previous pairwise analyses. By synthesizing a broader range of studies than previously available, we have strengthened the robustness of the pooled estimates and, through the unique advantages of network meta-analysis, provided a preliminary, probability-based ranking of treatments based on the current body of evidence.

This network meta-analysis was conducted to evaluate the comparative effectiveness and safety of the three fixation methods—FNS, CCS, and DHS. Our primary research question was: In patients with femoral neck fractures, which internal fixation method demonstrates superior clinical efficacy (as measured by the Harris Hip Score) and a more favorable safety profile, particularly regarding the risks of femoral neck shortening, femoral head necrosis, implant failure/cut-out, and fracture nonunion/delayed union?

The article is organized into the following sections. The Methods section describes the search strategy, study selection criteria, data extraction, risk-of-bias assessment, and statistical synthesis. The Results section reports the characteristics of the included studies, the pooled results, and the treatment rankings. The Discussion section interprets the key findings in a clinical context and discusses the limitations of the evidence. Finally, the Conclusion section summarizes the principal conclusions and suggests directions for future research.

This study followed a registered protocol with PROSPERO (registration number: CRD420251014243), with one amendment implemented during the screening phase (rationale documented in the registry), and adheres to the Preferred Reporting Items for meta-analysis (PRISMA) guidelines (22).

This network meta-analysis was conducted to evaluate the comparative effectiveness and safety of FNS, CCS, and DHS for femoral neck fractures, with the aim of determining the optimal fixation strategy. Our findings, within the constraints of the available data, indicate that no single method was universally superior across all outcomes, but each demonstrated distinct strengths: FNS significantly outperformed CCS in HHS and fracture healing time, while also significantly surpassing DHS in operative time and femoral head necrosis. DHS showed significantly lower risks of implant failure/cut-out and fracture nonunion/delayed union compared to CCS, with comparable performance to FNS. CCS demonstrated significant superiority over DHS in femoral head necrosis and operative time, while also showing a significant reduction in intraoperative blood loss compared to both DHS and FNS. However, given that the CINeMA assessment indicated generally low or very low certainty of evidence for most comparisons, the P-score rankings which offer a probability-based hierarchy of relative treatment performance should not be equated with definitive clinical superiority, especially for outcomes with small, non-significant, or highly heterogeneous between-treatment differences. Therefore, clinical decision-making should prioritize specific effect estimates, confidence intervals, and patient-centered goals over the rank order itself.

Our network meta-analysis found that FNS yielded significantly higher HHS compared to CCS, aligning with findings from Jiang et al. and Patel et al. (18, 59). The superior HHS observed with the FNS may be attributed to its capacity to prevent femoral neck shortening while mitigating complications, including femoral head necrosis and implant failure/cut-out. Substantial evidence indicates that femoral neck shortening markedly compromises hip function and quality of life. Mechanistically, this results from reduced moment arms of hip abductor muscles, causing limping and weakened abduction strength that collectively impair hip function (60). Furthermore, femoral head necrosis and fixation failure induce hip pain and restricted motion at varying severity levels, thereby directly diminishing HHS outcomes (61, 62). While the FNS showed a statistically significant improvement in HHS over CCS (mean difference 3.79), this change remains below the reported Minimal Clinically Important Difference (MCID) of 6–10 points for HHS in this population (63–65). Although the result suggests a positive trend, its clinical relevance at the individual level is likely modest. Therefore, when choosing a treatment, this potential functional benefit of FNS should be weighed against its complication risks, cost, and technical demands. The considerable heterogeneity observed in HHS outcomes underscores the potential role of fracture type as an effect modifier, as suggested by our subgroup analysis of mixed populations (Garden I-IV/II-IV). Unfortunately, the available literature’s lack of outcome stratification by fracture subtype prevented a more granular analysis. Consequently, our findings should be interpreted with caution. Future high-quality research focusing on specific fracture types is essential to definitively elucidate the comparative effectiveness of these three fixation devices on HHS, providing tailored guidance for clinical implant selection.

For femoral neck shortening, although no statistically significant differences were observed among the three fixation techniques, the odds ratios suggested a potential hierarchy: DHS demonstrated marginally superior outcomes relative to FNS, with CCS showing the least favorable results. It is important to note that the considerable heterogeneity and the sparse, inconsistent high-quality evidence necessitate a cautious interpretation of these results. Evidence suggests that fracture type (Garden III–IV) and reduction quality (III–IV) are key predictors of postoperative femoral neck shortening, potentially explaining the significant heterogeneity in our findings (66–68). Demographic variations may represent another source of heterogeneity. Older patients with osteoporosis frequently demonstrate compromised bone quality, prolonged fracture healing, and poorer implant stability. These factors increase susceptibility to deformation during weight-bearing, consequently leading to femoral neck shortening (69, 70). Unfortunately, the limited number of available studies precluded meaningful subgroup analysis. Further studies are necessary.

The significantly higher incidence of femoral head necrosis observed with DHS compared to CCS and FNS stems from its larger bolt diameter. This design characteristic generates greater surgical trauma, necessitates more bone removal, and induces rotational displacement during insertion—all factors contributing to impaired femoral head perfusion (13, 71, 72). In contrast, FNS’s smooth nail design and minimally invasive approach preserve blood supply. Furthermore, DHS demonstrated superior outcomes versus CCS for both implant failure/cut-out and fracture nonunion/delayed union. DHS converts vertical loads into axial compression at the fracture site via a sliding compression mechanism, enhancing interfragmentary compression and promoting fracture healing (73). Additionally, its larger lag screw diameter also increases bone-implant contact area and friction, reducing the risks of implant failure/cut-out and fracture nonunion/delayed union. FNS exhibited mechanical stability comparable to DHS with similar compression advantages (74, 75). Consequently, no significant differences were observed between FNS and DHS regarding implant failure/cut-out, fracture nonunion/delayed union, and fracture healing time. It should be noted that the pooled estimates for femoral head necrosis and fracture nonunion/delayed union were influenced by a single large retrospective registry study (Jetto et al.), which contributed substantial weight to these analyses. Sensitivity analysis excluding this study attenuated the DHS versus CCS comparisons for both outcomes to non-significance. However, the direction of effect remained consistent across both outcomes, and comparisons involving FNS were largely unchanged. These findings suggest that while the precision and statistical significance of the DHS versus CCS comparisons may be overestimated by the inclusion of this large study, the overall trends remain mechanistically plausible. Nevertheless, confirmation in future high-quality studies is warranted.

CCS demonstrated the lowest intraoperative blood loss, followed by FNS, with DHS exhibiting the highest volumes. Operative time was the longest for DHS, while FNS procedures were non-significantly shorter than CCS. Notably, FNS achieved this efficiency despite surgeons’ relative inexperience with this newer system, suggesting that it may offer greater ease of use compared to the established CCS and DHS techniques. The substantial heterogeneity observed likely stems from variations in patient age, which our meta-regression indicated was a significant moderator for blood loss, with the differences between treatments diminishing in older patients.

Notably, caution is required when extrapolating our findings to older adults. Although our study included adults across the age spectrum, subgroup analyses by age or osteoporosis status were not feasible. Since femoral neck fractures in the elderly are predominantly osteoporotic, their distinct bone-healing biology—such as impaired osteoblast function, aberrant stem cell activity, and a pro-resorptive microenvironment—may alter the healing response to different fixation devices (76, 77). Simultaneously, the degraded biomechanical environment, characterized by reduced bone mineral density and loss of trabecular connectivity, can directly compromise implant stability (78–80). Consequently, in osteoporotic bone, implant fixation strength, cut-out resistance, and control of micro-motion become paramount. Therefore, our primary findings may not directly inform decision-making for older osteoporotic patients, underscoring the urgent need for high-quality, targeted studies in this population. Moreover, the interpretation of these pooled estimates requires caution due to substantial statistical heterogeneity. Several outcomes in this analysis, including HHS, intraoperative blood loss, and fracture healing time, exhibited substantial statistical heterogeneity (I² > 90%). As noted in the preceding discussions, potential sources are multifaceted and may include clinical diversity (e.g., variations in patient age, displacement, osteoporosis status, and rehabilitation protocols) and methodological diversity (e.g., differences in surgical technique, follow-up duration, and study design). Notably, the predominance of retrospective cohort studies in our analysis (18 of 23, mostly moderate risk of bias) introduces residual confounding from unmeasured factors—such as fracture displacement and surgeon selection bias—that could not be fully accounted for. These methodological limitations likely contribute substantially to the observed heterogeneity. While random-effects models were employed to incorporate this between-study variance, the high heterogeneity fundamentally suggests that the pooled effect estimates should be interpreted as an average across a diverse set of clinical scenarios rather than a precise predictor for all individuals. This underscores the need for caution when generalizing these findings and highlights that clinical decision-making should remain tailored to specific patient and contextual factors.

While the FNS has shown promising results for femoral neck fractures, several concerns require urgent resolution, such as the potential for subtrochanteric fracture, unclear cost-effectiveness, and a substantial lack of long-term evidence. Firstly, clinical case reports have suggested a potential risk of subtrochanteric fractures with the FNS (81, 82). This hypothesis is further corroborated by several biomechanical studies. Fan et al. demonstrated that the peak von Mises stress on the distal locking screw of the FNS in the lesser trochanteric region reaches approximately 80 MPa—higher than that observed with three CCS (83). Similarly, Jung et al. found that a longer lateral plate length and a valgus bolt position elevate cortical bone strain around the distal-most locking screw in FNS, consequently increasing the risk of subtrochanteric fracture (84). However, as the available evidence on FNS-related subtrochanteric fractures is largely confined to biomechanics and lacks clinical data, high-quality clinical studies are required to clarify the incidence and influencing factors of this complication. Secondly, cost-effectiveness plays an important role in clinical decisions. However, there is currently no cost-effectiveness analysis evidence demonstrating that the significantly higher price of FNS over three CCS can be offset by commensurate benefits (85). Finally, as a relatively new technology, FNS has a limited history of clinical application, and its optimal clinical indications-such as appropriate patient age and specific fracture types-remain undefined. A study initiated by the AO Foundation found that in younger patients under 58 years, HHS were uniformly good to excellent. In contrast, the distribution of HHS in patients aged 58–80 years was similar to that in those over 80 years, ranging widely from 25 to 100 (86). This indicates that postoperative functional recovery with FNS is superior in younger populations compared to older adults. This observation is consistent with the results of our meta-regression analysis, which demonstrated that the difference in postoperative functional outcomes between FNS and the other two internal fixation devices diminishes with increasing patient age. This attenuated benefit may be attributed to a reduction in the biomechanical stability provided by FNS in older patients particularly those with osteoporosis, which is even inferior to that of CCS (87). Consequently, the clinical application of FNS in elderly or osteoporotic patients should be cautious until high-quality RCTs are conducted to definitively establish its safety and efficacy in these specific populations. Furthermore, most existing studies are retrospective cohort analyses with relatively short follow-up periods, making it difficult to accurately assess the long-term incidence of complications such as femoral head necrosis and implant failure. Therefore, further high-quality, long-term studies are essential to evaluate the safety and efficacy of FNS and to define its optimal clinical applications.

Given the current evidence, clinical implant selection must be individualized based on their distinct efficacy-safety profiles. The FNS demonstrates advantages in promoting early function and healing, particularly for younger patients or those with displaced fractures where its biomechanical stability is most beneficial. Caution is advised for elderly or osteoporotic patients pending long-term safety data. The DHS provides reliable mechanical stability with a lower risk of implant failure and nonunion compared to CCS, making it a robust choice for unstable fracture patterns. However, its greater risk of femoral head necrosis necessitates careful consideration, especially in subcapital or transcervical fractures. The CCS remains the standard for minimally invasive fixation of non-displaced fractures, particularly when minimizing surgical trauma and blood loss is paramount. These recommendations are tempered by critical evidence gaps that must be addressed in future research: (1) long-term comparative safety, especially regarding subtrochanteric fracture risk with FNS and avascular necrosis across all implants; (2) stratified efficacy data for key but poorly reported modifiers, including precise osteoporosis status, fracture reduction quality, age, and specific displacement patterns; and (3) formal cost-effectiveness analyses. Until such high-quality, granular evidence emerges, a cautious and patient-tailored approach to implant selection, guided by surgeon expertise, remains prudent.

This network meta-analysis demonstrates that FNS shows potential benefits over CCS and DHS in terms of fracture healing time and reduced risk of femoral head necrosis. Regarding HHS, FNS was statistically superior to CCS, but the magnitude of improvement did not reach the minimal clinically important difference, suggesting limited clinical meaningfulness. Several limitations remain, such as uncertain clinical indications, an unclear risk of subtrochanteric fracture, and the absence of high-quality, long-term follow-up studies. Therefore, until more high-level and robust evidence becomes available, clinicians should adopt a selective and judicious approach to its use. Future large-scale, prospective studies are essential to definitively determine its clinical superiority and establish guidelines for its optimal use.