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

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 mm³ vs. 3215.20 ± 1524.84 mm³), 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 mm³ 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.