Factors associated with cam deformity in Japanese local residents

Femoroacetabular impingement has increasingly been recognized as a cause of primary hip osteoarthritis; however, its epidemiological indications remain unclear. We aimed to clarify the epidemiological indications and factors associated with cam deformity in a large-scale population-based cohort in Japan. Overall, 1,480 participants (491 men, 989 women; mean age, 65.3 years) analyzed in the third survey of the Research on Osteoarthritis/Osteoporosis Against Disability study were included. The α angle and spinopelvic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic tilt, and pelvic incidence) were radiographically measured. Cam deformity was defined as an angle ≥ 60°. Overall, 7.3% of patients had cam deformity on at least one side. Cam deformity prevalence tended to increase with age; a higher percentage of men was observed in the group with cam deformity than in that without it in the univariate analysis. LL and SS were significantly lower in the group with cam deformities. No relationship was observed between cam deformity and hip pain. Factors associated with α angle were examined via multiple regression analysis; α angle was significantly associated with age and male sex. Thus, α angle and cam deformity prevalence increase with age in Japanese individuals. Accordingly, cam deformity can be a developmental disease.