Greater three‐dimensional cam burden and superolateral location are associated with end‐stage hip osteoarthritis: A retrospective comparative study

Abstract Purpose Cam‐type femoroacetabular impingement (FAI) is a recognised structural contributor to primary hip osteoarthritis (OA), yet many cam‐positive hips do not progress to radiographic joint failure. This study aimed to compare three‐dimensional cam morphology and lesion location between cam‐positive hips with end‐stage primary osteoarthritis and cam‐positive, non‐arthritic hips in an elderly fracture cohort. Methods Hospital records and imaging archives from January 2020 to January 2026 were retrospectively reviewed at a single centre. The OA group comprised patients undergoing total hip arthroplasty for primary OA, and the fracture group comprised patients aged ≥ 65 years treated for intertrochanteric or subtrochanteric femoral fractures without radiographic OA. Cam morphology was characterised using radial CT‐based alpha angle, three‐dimensional cam volume, cam/head volume ratio, and clock‐face–based lesion location. Group comparisons, receiver operating characteristic analyses, correlation testing, and multivariable logistic regression were performed. Results A total of 438 cam‐positive hips were included (126 OA and 312 fracture). OA hips demonstrated higher alpha angles (72.44° ± 5.94° vs. 62.45° ± 5.07°), larger cam volumes (5274.77 ± 1353.26 mm 3 vs. 3215.20 ± 1524.84 mm 3 ), higher cam/head ratios (8.61% ± 2.02% vs. 6.35% ± 1.97%), and more superolateral lesions (52.4% vs. 36.2% anterior in the fracture group) (all p  < 0.001). Exploratory receiver operating characteristic analyses identified cohort‐specific discriminatory values of 66° for alpha angle (AUC, 0.884), 4421 mm 3 for cam volume (AUC, 0.839), and 6.4% for the cam‐to‐head volume ratio (AUC, 0.791). In multivariable analyses using continuous morphology measures, higher alpha angle, greater cam volume, higher cam‐to‐head volume ratio, and superolateral lesion location were associated with end‐stage OA‐group membership. Conclusions Compared with non‐arthritic cam‐positive hips in an elderly fracture cohort, end‐stage primary OA hips had greater three‐dimensional cam burden, with lesions more often located superolaterally. These retrospective associations do not establish longitudinal progression, causality, or individual prognosis. Study Design Retrospective comparative study. Level of Evidence Level III, study of a non‐consecutive patients, study of diagnostic test.