Radiographic Cam Morphology of the Hip May Be Associated with ACL Injury of the Knee: A Case-Control Study

PURPOSE: To evaluate femoral and acetabular morphology in patients who underwent anterior cruciate ligament reconstruction (ACLR). METHODS: A retrospective review of a prospectively collected ACL registry was performed to identify patients with pelvis radiographs before undergoing either primary or revision ACLR between January 2010 and August 2020. Alpha angle (AA), head-neck offset ratio (HNOR), lateral center edge angle (LCEA), and crossover sign (COS) were measured on the operative side. Values were compared to a negative control group that did not significantly differ in age, sex, or body mass index. Univariate analysis and Pearson’s correlation coefficient were used to compare groups with significance defined as P < .05. RESULTS: In total, 114 patients were included (ACL, n = 38; control, n = 76). Eleven primary and 27 revision ACL reconstructions were identified. The mean AA in patients undergoing primary ACL reconstruction was higher than control (67.45° ± 11.30° vs 51.5° ± 10.8°, P < .001). A significantly elevated AA was also found in those undergoing revision ACL surgery (61.8° ± 7.51° vs 51.5° ± 10.8°, P < .001). In addition, the HNOR was significantly lower in the ACL group (0.12 ± 0.03 vs 0.14 ± 0.04, P = .0304). Acetabular morphology was similar between groups (LCEA, ACL 31.97° ± 5.04° vs control 30.01° ± 5.17°, P = .0549; COS, ACL 9 of 38 (23.7%) vs control 18 of 76 (23.7%), P = 1.00). CONCLUSION: An association exists between radiographic cam morphology of the hip and patients who previously underwent ACLR. LEVEL OF EVIDENCE: III, retrospective comparison study.