Impingement simulation of the hip in SCFE using 3D models.

Objective: Affecting as it does the geometry of adolescent hips, slipped capital femoral epiphysis (SCFE) and its evaluation represent a major three-dimensional problem. The current methods of clinical assessment-geometric measurements of the femur on plain radiographs or on axial computed tomographic (CT) cross-sections-address only one of the two joint components.
Materials and Methods: We have developed a system to simulate motion of hip joints with physiologic joint contact. In our system, CT-based computer models of the femur, pelvis, etc., are fitted with oriented bounding boxes (OBBs) and manipulated. Collision detection algorithms control the hip motion, which, in this virtual joint, is based on the surface geometry of the joint partners rather than on a predefined fixed rotation center.
Results: An illustrative case is presented to show the advantages of the new biomechanical evaluation method over conventional radiological assessments for SCFE. The proposed system provides remarkably high speed, and the necessary data can be prepared in a reasonable time.
Conclusion: The range-of-motion assessment provides the surgeon with information about the site and the impact of nonphysiologic contact in the hip joint. The information thus obtained can be valuable for indication and planning of corrective surgery in cases of SCFE.
(Copyright 1999 Wiley-Liss, Inc.)