• BACKGROUND
    • Accurate component positioning is the key for successful outcome after total hip arthroplasty (THA). Positioning acetabular and femoral components in a safe zone of 25°-50° on the basis of combined anteversion (CA) has shown to reduce instability and impingement. This safe zone was described for THAs performed through the posterior approach and has not been validated for other surgical approaches.
  • METHODS
    • Seventy patients who underwent unilateral uncemented THA were included in the study; 35 patients-using posterior approach and the remaining 35-using trans-gluteal approach. All patients included had a stable and impingement-free THA at a mean follow-up of 39.2 ± 9.5 months. CT scan was performed to assess component positioning by calculating CA. The values were compared between the two groups to study possible differences.
  • RESULTS
    • CA in the trans-gluteal group was significantly lower (32° ± 3.7° vs 38.4° ± 4.6°, P < .001) compared to posterior group. The difference in CA was due to the differences in acetabular anteversion, which was significantly low in the trans-gluteal group than the posterior group (22.1° ± 3.6° vs 27.8° ± 4.2°, P < .001). The mean femoral anteversion was similar in both groups. All trans-gluteal hips fell within the safe zone of 20°-40°, and all posterior hips fell within the safe zone of 25°-50°.
  • CONCLUSION
    • A safe zone of 25°-50° is valid for THAs performed from the posterior approach but not universally applicable. For trans-gluteal approach, a safe zone of 20°-40° is better to provide a stable and impingement-free THA. CA varies with the surgical approach. THAs performed through the trans-gluteal approach can be stable and impingement-free with lesser CA compared to THAs performed through the posterior approach.