A knowledge-based approach to the CAD/CAM of cementless total hip replacement

The use of computer graphics (CAD) to position components for preoperation decision-making in total hip replacement has been investigated. Radiographs of the diseased joint are taken, one in the anterior-posterior (AP) direction and the other in the medial-lateral (ML) direction. Using a back-lit digitizing tablet, the affected joint is outlined on the video display unit (VDU), and the contour data are used to create a three-dimensional model of the proximal femur and acetabulum on the VDU and then stored in memory. In the event of failure to find a standard arthroplasty from memory, a custom-designed prosthesis can be developed. Using an object-oriented approach, a user identifies the item (object) and then sends messages telling it to erase, move, and display. A designer can alter performance characteristics or parameters of components and see the implications of modification reflected throughout the whole design.< >