Spinopelvic Characteristics as Predictors of Cam Morphology: A 2-Year Follow-up of Elite Adolescent Soccer Players

Abstract

Background: Cam morphology develops gradually during the end stages of skeletal maturity before hip physis closure. It has been shown to be a risk factor for early-onset hip pain and joint degeneration.

Purpose: To (1) evaluate the differences in spinopelvic parameters between elite adolescent soccer players at baseline and follow-up and (2) discern whether certain parameters can predict the development of cam morphology over time.

Study design: Cohort study (prognosis); Level of evidence, 2.

Methods: This prospective 2-year follow-up study involved elite soccer players aged 12 to 16 years (baseline: n = 29; follow-up: n = 20). At both baseline and follow-up, anteroposterior and 45° Dunn views were used to assess skeletal maturity and the presence of cam morphology to classify participants into the cam group or no cam group. Low-dose biplanar scans obtained in the standing, sitting, and squatting positions were used to determine pelvic incidence, sacral slope, sagittal pelvic tilt, lumbar lordosis, and pelvic-femoral angle. Differences in these parameters between the 3 weightbearing positions were used to calculate relative pelvic movement and relative hip flexion percentages.

Results: At baseline and follow-up, 55.2% of participants had cam morphology (right hip: n = 16; left hip: n = 15). Significant differences were observed between the cam and no cam groups at both time points in pelvic incidence (baseline: 50.5°± 5.1° vs 42.7°± 6.8°, respectively; P = .01) (follow-up: 52.8°± 7.9° vs 43.8°± 8.0°, respectively; P = .01), sacral slope while squatting (baseline: 29.0°± 8.6° vs 17.9°± 12.3°, respectively; P = .024) (follow-up: 27.5°± 10.0° vs 21.0°± 8.9°, respectively; P = .031), and relative pelvic movement while squatting (baseline: 32.4% ± 11.2% vs 47.4% ± 20.1%, respectively; P = .032) (follow-up: 38.4% ± 6.7% vs 45.3% ± 11.1%, respectively; P = .046). No significant changes were shown within groups longitudinally. On mixed-model logistic regression, pelvic incidence significantly predicted the development of cam morphology (estimate, 0.167; odds ratio, 1.182 [95% CI, 0.029-0.306]; P = .019).

Conclusion: Adolescent soccer players with cam morphology exhibited different spinopelvic characteristics compared with those without cam morphology, especially on imaging while squatting. The stability of the spinopelvic parameters longitudinally and the suggested causal relationship between increased pelvic incidence and the development of cam morphology could inform early screening protocols.

Keywords: femoroacetabular impingement; hip/pelvis/thigh; lumbar spine; pediatric sports medicine.