Computer-assited planning of corrective osteotomies in cases of slipped capital femoral epiphysis

Slipped capital femoral epiphysis (SCFE) leads to an unphysiologic function in adolescent hips. Evaluation of the slippage as well planning of correct ive osteotomies is a major three-dimensional (3D) problem. Therefore, the c urrent clinical evaluation, which is based on biplanar plain radiographs, c annot be satisfying. More is needed than simply measuring the femoral geome try to evaluate the impact of a slippage onto the physiologic hip function. We have developed a computer-based system for planning and evaluation of re orienting osteotomies in severe cases of SCFE. In our system, CT-based 3D c omputer models of the hip are used to simulate the range of motion within p hysiologic cartilage-to-cartilage contact. This helps to visualize and quan tify 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 fo r indicating and planning corrective osteotomies than conventional methods.