Femoral neck anteversion- what's normal in Indians: a morphological study of 742 hips using CT-based MAKO robotic evaluation.

BACKGROUND

Femoral neck anteversion (FNA) is a key determinant of hip biomechanics and component positioning in total hip arthroplasty (THA). Most reference values for femoral version are derived from Western populations and non-robotic measurement techniques. Data defining native femoral version in the Indian population using CT-based robotic planning are limited.

METHODS

This multicenter cross-sectional study analyzed 742 hips undergoing primary robotic-assisted THA using the MAKO THA 4.0 system. Native femoral version was calculated automatically from preoperative CT scans as the angle between the femoral neck axis and the trans-epicondylar axis. Femoral version was categorized as retroversion (< 0°), neutral (0°), or anteversion (> 0°). Descriptive statistics were reported as Mean (SD). Group comparisons were performed using chi-square tests, with statistical significance set at p < 0.05.

RESULTS

The mean native femoral version was - 2.6° (SD 11.9), with a range from - 42° to 41°. Overall, 395 hips (53.2%) demonstrated retroversion, 320 hips (43.1%) anteversion, and 27 hips (3.6%) neutral alignment. Retroversion predominated in males, whereas females showed significantly higher anteversion (p < 0.001). No statistically significant differences were observed across age groups (p = 0.310; Spearman ρ = 0.034, p = 0.356) or diagnosis categories (p = 0.227). Notably, 703 hips (94.7%) demonstrated femoral version below 15°.

CONCLUSION

Indian patients undergoing THA demonstrate substantially lower femoral neck anteversion than commonly cited Western norms, with more than half exhibiting femoral retroversion. These findings highlight the importance of population-specific and individualized preoperative planning, for which CT-based assessment can be useful.