A study of femoral offset in the South Indian population and its clinical implications in hip arthroplasty

Background Recreation of the normal proximal femoral anatomy is paramount for a successful total hip arthroplasty. The study aims to look at whether the range of offset options available in the femoral stems available locally, would be adequate to restore the native femoral horizontal offset (FHO) of the South Indian population. Method This is a prospective single-center study of 1-year duration, where we study the FHO on radiographs and CT scans in 100 patients. We then look at the femoral stems available in the Indian market and see if the offset may be restored with the available stems. Result The FHO ranged from 23.3 to 46.9 mm with a mean of 35.7 ± 5.3 mm. The females in the group (33.86 ± 4.71 mm) had a lower FHO compared to males (37.78 ± 5. 21 mm). We found that 50% of the South Indian population and 62% of the females have an offset less than 35 mm. Among the 18 stems that we studied, four out of nine cemented and two out of nine uncemented stems did not offer an offset below 35 mm. Conclusion The native FHO in the South Indian population is significantly less than that of Caucasians. The surgeon should be aware that many implant systems available in India do not offer offset options in this range. In this group, even when a stem with smallest offset is used, there is a risk of increasing the FHO with a potential for intraoperative fractures due to difficult reduction and leg-lengthening. Hence, the surgeon should template carefully and choose only those implant systems which can offer an offset similar to the native offset to restore the anatomy accurately. We recommend that all manufacturers consider offering implants with smaller offset (25–35 mm).