Evaluation of Spine Hip Relation and its Correlation as a Guide to Total Hip Arthroplasty.

AIMS AND

BACKGROUND

Dislocation remains one of the most common complications following total hip arthroplasty (THA). Although the classical "Lewinnek's safe zone" for acetabular cup positioning has long guided surgeons, a considerable number of dislocations still occur even within this zone. Recent evidence emphasizes the importance of the dynamic spinopelvic relationship, specifically variations in pelvic tilt and functional anteversion, which directly influence acetabular orientation and joint stability. This study aims to analyze the spinopelvic relationship and its effect on acetabular cup anteversion and femoral head coverage in THA.

MATERIALS AND

METHODS

A total of 30 patients aged between 20 and 70 years undergoing primary THA were included in the study. Pre-operative assessment involved X-rays of the lumbar spine and pelvis in both supine and standing positions to determine changes in pelvic tilt. Acetabular anteversion was modified accordingly. Postoperatively, acetabular cup positioning and femoral head coverage were evaluated radiographically using the Woo and Morrey method for anteversion and the lateral center edge angle (LCEA) of Wiberg. Statistical analysis was performed using the Statistical Package for the Social Sciences version 23.

RESULTS

The mean pelvic tilt in supine and standing positions was -3.30° and -5.77°, respectively, with a mean change of -2.44°. The mean target anteversion was 13.32°, and the mean achieved anteversion was 14.65°. The mean LCEA was 50.51°. A weak negative correlation was found between anteversion achieved and LCEA (ρ = -0.27, P = 0.141). The LCEA was highest when acetabular anteversion was within 5°-25°, suggesting optimal femoral head coverage within this range.

CONCLUSION

The study highlights that a fixed "safe zone" for acetabular cup placement is insufficient. Individualized cup orientation based on spinopelvic parameters enhances joint stability and femoral head coverage. Functional assessment of pelvic tilt and anteversion should be integrated into pre-operative planning to reduce the risk of impingement and dislocation in THA.