Acetabular posterior wall morphology in slipped capital femoral epiphysis: a three-dimensional and true axial computed tomography matched-cohort study

AIMS: Comparative assessment of both hip joints in patients with slipped capital femoral epiphysis (SCFE) was performed relative to the control group. METHODS: We created 3D CT reconstructions of the acetabulum in 27 hips with SCFE, 21 unaffected contralateral hips, and 108 hips of the age- and sex-matched non-SCFE control group. Following measurements performed using true axial CT scans were assessed: acetabular version angle (AVA°), posterior sector acetabular angle (PASA°), posterior wall angle (PWA°), and acetabular roofing percentage. RESULTS: Based on the morphology of the posterior acetabular wall, we found three type I (closed) and 24 type II (open) hips in the SCFE group. We noticed a flattening of the posterosuperior quadrant of the acetabulum in 66.66% (18 out of 27 hips) of the hips affected by SCFE. For both SCFE (p = 0.004) and unaffected hips (p = 0.009), the AVA at the proximal hip level was significantly lower than in the control group. We observed no significant between-group differences in PASA (p > 0.05). The mean values of the PWA for the SCFE group were significantly higher than in the contralateral hip (p = 0.025) and control group (p = 0.018). None of the patients in our cohort met the criteria for hip dysplasia based on the assessed Tönnis angle (TA) and lateral centre-edge angle (LCEA). CONCLUSIONS: Hips with SCFE tend to be flattened at the posterosuperior quadrant and have higher PWA values. PWA better defines the morphology of the posterior wall than the PASA. As the PWA angle increases, the mechanical shearing forces at the femoral physis may increase; however, this requires further research.