Stereographic processing of CT figures in the hip joints

CT scan is widely used in orthopedic examinations. By three-dimentional display of the form of bone and joint, the change of form can be identified and the lesion can be located. CT figures were stereographically processed using a personal computer to display the images of the hip joints. The outlines of the bone seen on the CT film were directly traced with a digitizer, then the A/D converted coordinate data were obtained. The data for each slice were input to the personal computer. After conversion to normal coordinate and magnification, the data were filed on the floppy disc. These data were regained from the disk and made affin transformation to display the stereographic images of the hip joints. In a case of solitary bone cyst of the coxal bone, this method helped us to decide the appropriated surgical approach. For the congenital dysplasia of the hip, acetabular coverage was examined three-dimensionally and postoperative changes were assessed in the cases of shelf operation and intertrochanteric extension osteotomy. In the cases of aseptic necrosis of the femoral head, location and size of the necrotic area were clearly visualized and the appropriate surgical procedure could be decided. Moreover, it was useful to decide the degree of rotation of the femoral head in rotational osteotomy. (author) 61 refs