Computer aided design of individualized hemipelvic prosthesis and its clinical application

Objective To summarize the experience in CAD / CAM custom-made hemipelvic prosthesis and its application in 8 patients. Methods The exact model of pelvis was generated with its CT data by Rapid Prototyping Technique (RPT). Simulated bone resection and prosthesis design were performed on the models. The prosthesis should be fixed simultaneously on the contralateral pubic ramus (or the remainder of pubis), the joint facet of sacrum (or the remainder of ilium) and on the remained ischium if part of it could be preserved. When prosthesis was put in place, the acetabular component should be symmetric with the contralateral acetabulum in terms of the height, lateral distance and abduction angle, after it's fixation on the remained pelvis with cancellous screws, bolts and hooks, conventional total hip implants with cemented acetabular and cementless femoral prothesis were implanted. 8 patients underwent this kind of procedure, of them 7 suffered from large pelvic tumor, including 2 chondrosarcoma, 3 giant cell tumors, 1 cartilaginous fibrodysplasia and 1 metastasis. One patient received this procedure for severe osteolysis after THA. Tumor artery embolization was done in 6 of them 24-48 h before operation. Results Blood transfusion was 4971 ml in average. The implantation of prosthesis was easily accessible. One suffered from remained sinus, and healed after myocutaneous flap transferring. All patients began non-weight bearing walk with double crutches 6 weeks after operation and gradually abandoned crutches in 3 months. One patient with chondrosarcoma died of lung metastasis 9 months after operation. No loosening was found during the 1 to 4 years (2.5 years in average) follow-up of the 7 cases. The position of bilateral hips was symmetric. They all recovered to self-care. Two of them returned to work 7 and 8 months after operation respectively. One local recurrence happened and was resected again. Conclusion The custom-made hemipelvic prosthesis generated with RPT and CAD/CAM can improve the prosthesis fixation, ensure the exact orientation of acetabular component and make the operation easy.