PROCESS FOR MAKING CUSTOM JOINT REPLACEMENTS

A process for forming a prosthesis related to bone structure internal to a body using CT scan data corresponding to the radiological density of the bone structure to derive the inner and outer bone surface contours. The density and the density gradient of discrete points in the bone structure compared to threshold density levels and to threshold density gradient levels and points are selected to form a series of interim outer contours. A contour shape factor is derived for each interim outer contour, and that interim contour is chosen in which the contour shape factor is maximum denoting less fluctuations in the contour circumference. The bone surface contour data is used to develop a graphic model from which a set of digital data is generated for a surface model representing the graphic model. A set of numerical control machine instructions are generated to make the prosthesis.