Hip morphology in slipped capital femoral epiphysis

Several mechanical factors have been related to slipped capital femoral epiphysis (SCFE). Main aim of this study is to investigate the acetabular coverage and acetabular version in unilateral SCFE hips in order to detect a potential pincer-type deformity as predisposing factor; second, we compared those measurements either to the contralateral, uninvolved hips either to a matched healthy control population. A total of 85 patients treated for unilateral SCFE were retrospectively reviewed. The lateral center-edge angle (LCEA) and the Tönnis angle were used to assess acetabular coverage, whereas acetabular retroversion was defined by positive prominent ischial spine (PIS), cross-over sign (COS) and posterior wall sign (PWS). Angles and signs of the affected hips were compared to the contralateral hips and to a matched cohort undergoing an abdominal/pelvic computed tomography for nonorthopedic-related diseases. Affected and unaffected hips of patients with unilateral SCFE had similar morphology in terms of LCEA 28.7° vs. 28° (P = 0.4), Tönnis angle 9° vs. 9° (P = 0.1) and retroversion signs with concomitant rate of PWS and COS 57.6% vs. 50.5% (P = 0.4), PIS 56.4% vs. 49.4% (P = 0.4). Matched healthy controls vs. the affected hips showed a lower LCEA (P < 0.001) and higher Tönnis angle (P < 0.001) in conjunction with a lower incidence of acetabular retroversion: PWS and COS 40% vs. 57.6% (P = 0.01), PIS 43% vs. 56.4% (P = 0.07). A significant retroversion and increased overcoverage were observed in SCFE patients compared to matched healthy controls. In unilateral SCFE, the involved and uninvolved hips showed a substantial symmetry.