Perioperative changes in pelvic tilt after hip resurfacing using a direct lateral approach

Linsen T. Samuel, Jared Warren, Jacob M. Rabin, Alexander J. Acuña, Amy Shuster, Jordan Patterson, Michael A. Mont, Peter J. Brooks


Background: Proper positioning of the acetabular component is critical for prevention of dislocation and excessive wear for total hip arthroplasty (THA) and hip resurfacing. Consideration of preoperative pelvic tilt (PT) may aid in acetabular component placement. The purpose of this study was to investigate how PT changes after hip resurfacing, via pre and post-operative radiographic analysis of anterior pelvic plane (APP), and whether radiographic analysis of the APP is a reproducible method for evaluating PT in resurfaced hips.
Methods: A consecutive group of 228 patients from a single surgeon who had hip resurfacing were evaluated. We obtained X-rays from an institutional database for these patients who had their surgeries between January 1st, 2014 to December 31st, 2016. PT was measured by two observers before and after resurfacing utilizing a standardized radiographic technique. Correlation coefficients were calculated for PT measurements between observers, and pre- and post-surgery.
Results: Mean preoperative PT was 0.7° (SD ±6.6°) and 0.4° (SD ±6.1°). Mean post-operative PT was −1.2° (SD ±6.2°) and −1.2° (SD ±6.0°). Correlations between pre and post-operative PT were R=0.829 (P<0.001) and R=0.837 (P<0.001). 80.6% to 82.5% of patients had variation <5°, 15.8% to 17.8% had variation between 5–10°, and 1.6% to 1.8% had a variation >10°. Intraclass correlation coefficients between observers were R=0.987 (95% CI, 0.963–0.981; P<0.001) preoperatively, and R=0.985 (95% CI, 0.963–0.981; P<0.001) postoperatively.
Conclusions: After hip resurfacing arthroplasty (HRA), the mean difference between preoperative and postoperative PT was less than 1°. These results suggest that near-native PT is maintained with consistency after hip resurfacing, a finding that is variable following THA. Since variations in PT affect functional acetabular position, these results support the use of PT measurement in pre-operative planning for hip arthroplasty with a high degree of inter-observer reliability.