Changes in spinopelvic indices after hip arthroplasty and its influence on acetabular component orientation.

Objective: To evaluate spinopelvic changes after hip arthroplasty in standing and ready-to-rise positions.

Methods: We compared pelvic tilt, sacral slope, cobb's angle, and hip flexion on pre and postoperative spinopelvic radiographs.

Results: Standing: All postoperative indices were similar to preoperative ones except sacral slope (mean difference:1.6°, p = 0.046). Ready-to-rise: All postoperative indices were similar to preoperative ones except pelvic tilt which was significantly greater postoperatively (mean difference: 5.1°, p = 0.017). Fifteen patients showed >10° increase in pelvic tilt postoperatively.

Conclusion: Changes in pelvic tilt in ready-to-rise position can predispose to posterior edge loading, edge wear, and dislocation; especially with inadequate cup anteversion.