Can the change in center-edge angle during pincer trimming be reliably predicted?

Background: Femoroacetabular impingement is recognized as a cause of hip pain in young adults and as a precursor to osteoarthritis although many questions persist regarding its management. One in particular is when to resect a pincer lesion and how much to resect. Instability can result from overresection and persistent impingement can result from underresection. Questions/purposes: We therefore determined the correlation between the change in center-edge (CE) angle and the amount of acetabular rim resection. Methods: We performed open acetabular rim trimming on 10 cadaveric hips. Radiographs were performed before and after rim resection every millimeter from 1 to 5 mm and we determined the CE angle. We performed linear regression to establish any correlation of the CE angle with the amount of resection. Results: The CE angle could be predicted by -1.3X + 1.5 (R ² = 0.99), in which X = the amount of resection for 1 to 3 mm of resection. The average CE angle before resection was 35° ± 8.8° (range, 19°-58°). Conclusions: The CE angle changes in a predictable way with acetabular rim trimming with larger amounts of resection resulting in greater changes in the CE angle. Clinical Relevance: The ability to accurately plan the amount of acetabular rim resection in hip arthroscopy by knowing the exact change in CE angle with amount of rim removal may help prevent overresection or underresection in pincer trimming.