Three-dimensional computerized tomographic analysis of the deformity of lateral growth disturbance of proximal femoral physis

BACKGROUND: Lateral growth disturbance of the proximal femoral physis after treatment of developmental dysplasia of the hip, also known as type 2 avascular necrosis, has been described in a 2-dimensional (2D) plane with standard radiographs. It is not well described in the 3-dimensional plane using 3D computed tomography (CT) scan. The purpose of this study was to define the anatomy of the proximal femur after the lateral growth disturbance of the proximal femoral physis with 3D CT scans. METHODS: Ten patients (11 hips) with lateral growth disturbance of the proximal femoral physis after treatment for developmental dysplasia of the hip (9 hips) and extracorporeal membrane oxygenation (2 hips), were studied with 2D and 3D CT methods. CT was done at an average age of 12.5 years (range, 9.8 to 16.69). RESULTS: In addition to the typical valgus configuration in the coronal plane, increased antetorsion of the femur (10 of 11 hips) and increased anteversion of the femoral head (8 of 11 hips) were a common finding seen in the transverse plane. In 6 of 7 hips for which the CT scan was performed before the closure of the capital femoral epiphysis, the physeal bridge was seen to be located in the anterolateral (5 hips) or posterolateral (1 hip) area of the proximal femoral physis. The version of the femoral head was correlated to the location of the physeal bridge. Acetabular dysplasia was seen in 4 hips. In the 3D reconstruction view, flexion deformity of the femoral head was seen in 6 hips and lack of coverage at the anterolateral portion of the femoral head was observed in 6 hips. CONCLUSIONS: The treating surgeon should be aware of the often marked antetorsion and also anteversion of the femoral head and neck associated with lateral growth disturbance of the proximal femoral physis. This knowledge allows surgical planning to correct rotational and sagittal plane correction of the proximal femur, which will allow normalizing hip mechanics. Acetabular side correction also may be needed if acetabular dysplasia is present. LEVEL OF EVIDENCE: Level III, diagnostic study.