[Computer-assisted planning of corrective osteotomies in cases of epiphysiolysis capitis femoris].

Slipped capital femoral epiphysis (SCFE) leads to an unphysiologic function in adolescent hips. Evaluation of the slippage as well planning of corrective osteotomies is a major three-dimensional (3D) problem. Therefore, the current clinical evaluation, which is based on biplanar plain radiographs, cannot be satisfying. More is needed than simply measuring the femoral geometry to evaluate the impact of a slippage onto the physiologic hip function. We have developed a computer-based system for planning and evaluation of reorienting osteotomies in severe cases of SCFE. In our system, CT-based 3D computer models of the hip are used to simulate the range of motion within physiologic cartilage-to-cartilage contact. This helps to visualize and quantify the early impingement due to the slippage. In addition, 3D techniques allow to simulate and plan the corrective osteotomy in an intuitive way on the computer screen. Using the same range of motion system mentioned above, the projected result can be evaluated quantitatively and compared to other approaches. The motion simulation is based on the surface geometry of the joint partners rather than on a predefined, fixed rotation center. The presented system allows a much more intuitive and appropriate system for indicating and planning corrective osteotomies than conventional methods.