Background: A cam deformity is a major risk factor for hip osteoarthritis, and its formation is thought to be influenced by high-impact sporting activities during growth.
Purpose: To (1) prospectively study whether a cam deformity can evolve over time in adolescents and whether its formation only occurs during skeletal maturation and (2) examine whether clinical or radiographic features can predict the formation of a cam deformity.
Study design: Cohort study (prognosis); Level of evidence, 2.
Methods: Preprofessional soccer players (N = 63; mean age, 14.43 years; range, 12-19 years) participated both at baseline and follow-up (mean follow-up, 2.4 ± 0.06 years). At both time points, standardized anteroposterior and frog-leg lateral radiographs were obtained. For each hip, the α angle was measured, and the anterosuperior head-neck junction was classified by a 3-point visual system as normal, flattened, or having a prominence. Differences between baseline and follow-up values for the α angle and the prevalence of each visual hip classification were calculated. Additionally, the amount of internal hip rotation, growth plate extension into the neck, and neck shaft angle were determined.
Results: Overall, there was a significant increase in the prevalence of a cam deformity during follow-up. In boys aged 12 and 13 years at baseline, the prevalence of a flattened head-neck junction increased significantly during follow-up (13.6% to 50.0%; P = .002). In all hips with an open growth plate at baseline, the prevalence of a prominence increased from 2.1% to 17.7% (P = .002). After closure of the proximal femoral growth plate, there was no significant increase in the prevalence or increase in severity of a cam deformity. The α angle increased significantly from 59.4° at baseline to 61.3° at follow-up (P = .018). The amount of growth plate extension was significantly associated with the α angle and hip classification (P = .001). A small neck shaft angle and limited internal rotation were associated with cam deformities and could also significantly predict the formation of cam deformities (α angle >60°) at follow-up.
Conclusion: In youth soccer players, cam deformities gradually develop during skeletal maturation and are probably stable from the time of growth plate closure. The formation of a cam deformity might be prevented by adjusting athletic activities during a small period of skeletal growth, which will have a major effect on the prevalence of hip osteoarthritis.
Keywords: adaptation; cause; femoroacetabular impingement; football (soccer); hip; osteoarthritis; pediatric sports medicine.