Acetabular Retroversion, but Not Increased Acetabular Depth or Coverage, in Slipped Capital Femoral Epiphysis

BACKGROUND: Femoral head overcoverage by a deep and retroverted acetabulum has been postulated as a mechanical factor in slipped capital femoral epiphysis (SCFE). We assessed acetabular depth, coverage, and version in the hips of patients with unilateral SCFE; in the contralateral, uninvolved hips; and in healthy control hips. METHODS: Thirty-six patients affected by unilateral SCFE were matched to 36 controls on the basis of sex and age. The acetabular depth-width ratio (ADR), the lateral center-edge angle (LCEA), the anterior and posterior acetabular sector angle (ASA), and version (10 mm distal to the highest point of the acetabular dome and at the level of the femoral head center) were assessed on computed tomography (CT). A repeated-measures analysis of variance was used to assess differences among the SCFE, contralateral, and matched-control hips. Pairwise comparisons were conducted using Bonferroni correction for multiple comparisons. RESULTS: The mean coronal ADR was significantly lower in the hips affected by SCFE (311.6) compared with the contralateral hips (336.1) (p = 0.001) but did not differ from that of controls (331.9) (p = 0.08). The mean LCEA was significantly lower in the SCFE hips (29.8°) compared with the contralateral hips (33.7°) (p 0.05) in acetabular measurements was observed between the contralateral and control hips. CONCLUSIONS: In SCFE, the acetabulum has reduced version but is not deeper, nor is there acetabular overcoverage. Additional longitudinal studies will clarify whether acetabular retroversion is a primary abnormality influencing the mechanics of SCFE development or an adaptive response to the slip. Our data suggest that the contralateral, uninvolved hip in patients with unilateral SCFE has normal acetabular morphology. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.