Sex-Based Differences in Femoral Neck Circumference: A Cadaveric Morphometric Study

Introduction Sex-based differences in femoral neck morphology may contribute to the disparate incidence of hip fractures between males and females. While prior studies have largely relied on imaging-based measurements, direct morphometric evaluation of femoral neck circumference in cadaveric specimens remains limited. This study examined sex-based differences in femoral neck morphology using a cadaveric model, with an emphasis on circumference as a novel direct measurement parameter. Materials and methods Twenty-five embalmed skeletally mature human cadavers (13 females, 12 males) were included. A total of 47 femora were extracted and measured, excluding femora with a prosthesis or hardware. Cadaver-level mean values were calculated by averaging bilateral measurements when available. Morphometric parameters included femoral neck circumference, neck-shaft angle, and femoral neck axis length. Independent-samples Welch t-tests were used to compare sex-based differences. Paired t-tests and Pearson correlation were performed to evaluate bilateral symmetry. Effect sizes were calculated using Hedges' g. Results Male cadavers demonstrated significantly greater mean femoral neck circumference compared to females (10.93 ± 0.64 cm vs. 9.45 ± 0.77 cm; Welch t(22.74) = 5.22, p < 0.001; Hedges' g = 2.00). No statistically significant sex-based differences were observed in neck-shaft angle (p = 0.47) or femoral neck axis length (p = 0.074). Strong bilateral symmetry was observed for femoral neck circumference (r = 0.88, p < 0.001). Conclusion Direct cadaveric measurement reveals clear sexual dimorphism in femoral neck circumference, whereas angular and linear dimensions show minimal sex-based differences. These findings suggest that circumferential cross-sectional geometry, rather than angular or linear morphology, may represent a meaningful axis of structural dimorphism in the proximal femur. Further biomechanical and imaging-based investigations incorporating femoral neck circumference are warranted.