Anatomical analysis and preoperative planning of correctional osteotomies:slipped capital femoral epiphysis (SCFE)

SCFE is defined as the slippage of the femoral head relative to the femoral neck along the proximal usually posteriorly and inferiorly. The pathoanato mical findings are characterised by the changed relationship between the fe moral head and femoral metaphysis, and between the femoral head and the ace tabulum. A reduced femoral anteversion, a varus deformity of the femur, a s hortening of the femoral metaphysis and an anterior metaphyseal prominence are also regularly observed. This may lead to impingement between the femor al metaphysis and the acetabular rim. Potential consequences of this comple x 3D deformity are pain, a reduced range of hip motion and an early degener ative joint disease, in moderate and severe cases a redirectional femoral o steotomy is recommended. Different techniques, such as subcapital, base-of- neck, intertrochanteric and subtrochanteric osteotomies, have been describe d. These correctional osteotomies aim towards a reconstruction of the hip j oint geometry, to prevent early arthritic degeneration. Currently, the plan ning of surgical treatment in these cases is based on measurements on anter o-posterior and lateral plain radiographs. The relevant angle for planning of correctional osteotomies is the physis-shaft angle, determined in both p lains. These angles describe the degree of slippage, thereby helping the su rgeon to indicate and plan a correctional osteotomy. However, plain radiogr aphs are projectional images and therefore carry inaccuracies caused by the overlay of anatomical structures and an incorrect positioning of the patie nt. 3D reconstructions are more accurate and provide substantial additional information for the surgeon, such as, for example, the anteversion of the acetabulum. We have developed interactive 3D software to measure projected angles, to analyse the geometry of the proximal femur and to determine the orientation of the acetabulum based on 3D reconstructions of CT data-sets. A program was also developed to simulate different techniques of osteotomie s and to evaluate the postoperative range of hip motion and the hip-joint g eometry. Accurate 3D measurements, additional anatomical information, simul ations of different techniques of osteotomies and the evaluation of simulat ed postoperative results enables the surgeon to determine the best surgical treatment, based on the clinical findings.