Does the femoral head/neck contour in the skeletally mature change over time?

The purpose of this study was to determine whether anterior/anterolateral femoral head/neck contour of the hip is static or dynamic over time within the context of the cam deformity. From a previously published cohort of 200 asymptomatic patients who had a magnetic resonance imaging (MRI) of their hips, 23 patients were randomly selected: 10 with a cam lesion and 13 with no evidence of a cam lesion in either hip. There were 7 females and 16 males with a mean age of 37.5 years (range 30–56 years). A repeat MRI or computed tomography scan was performed. Femoral head/neck contour was assessed with alpha angle measurements at the 3 and 1:30 positions. At mean time of 5.3 years (range 2.5–7.2 years) between the two time points, the mean alpha angle for the entire cohort was not significantly different with alpha angle of 43.4°/53.7° (3:00/1:30 positions) at first visit and 46.1°/54.2° (3:00/1:30 positions) at second visit, respectively. Subdividing the cohort into cam negative and cam positive groups, there are no clinically relevant differences (i.e. <5°) between the two alpha angle measurements. Inter-observer reliability had an intra-class coefficient at 0.96 (95% CI: 0.94–0.97). Neither group of patients demonstrated clinically relevant change in the alpha angle. Consequently, screening at time of skeletal of maturity would be an efficient means of identifying individuals for a possible cam deformity.