Objective To evaluate the surgical skill, cause of revision, compl ications, prosthetic survival and postoperative function in revision of custom-made tumor prosthesis replacement of knee joint. Methods The cl inical data of 33 patients who received prosthetic revision surgery between June 2002 and June 2007 were reviewed. There were 17 malesand 16 females with an average age of 33.1 years (range, 16-67 years). The pathological diagnosis included 17 osteosarcomas, 11 giant cell tumors, 2 mal ignant fibrous histocytomas, 1 chondrosarcoma, 1 synovial sarcoma, and 1 l iposarcoma. The involved locations were distal femur in 22 cases and proximal tibia in 11 cases. The average interval between first prosthetic replacement and revision surgery was 45.3 months (range, 6-180 months). The reason for revision included local recurrence in 2 cases, deep infection in 8 cases, aseptic loosening in 7 cases, peri prosthetic fracture in 1 case, prosthetic stem fracture in 6 cases, and prosthetic hinge failure in 9 cases. Six patients with deep infection received two-stage revision surgery, while the other 27 patients received one-stage revision. Cemented prostheses were used in all patients. Allograft prosthetic composite and revisions were used in 2 patients who had deficit of diaphysis for stem fixation. Results In 17 patients who received both primary prosthetic replacement and revision, the operative time was (149.8 ± 40.5) minutes and (189.9 ± 43.8) minutes, and the blood loss was (605.2 ± 308.0) mL and (834.1 ± 429.9) mL for primary prosthetic replacement and revision, respectively; all showing statistically significant differences (P lt; 0.05). The mean time of follow-up was 45.1 months (range, 12-76 months). Heal ing between allograft and host bone was obtained in 2 patients with allograft prosthetic composite and revision after 1.5 years and 2 years, respectively. After revision surgery, 3 patients died of lung metastasis after 12-24 months, and other 3 patients havinglung metastasis were al ive with disease. Nine (30%) compl ications occurred in 30 patients who were al ive at last follow-up. The compl ications included wound infection in 2 patients, deep infection in 5 patients, mechanical problems in 2 patients. Prosthetic failure occurred in 7 patients (23.3%). The 5-year survival rate of revised prosthesis was 68.6%. The Musculoskeletal Tumor Society (MSTS) score at 6 months after revision (73.6% ± 14.4%) was significantly improved (P lt; 0.01) when compared with before revision (57.1% ± 10.6%). Conclusion The main reasons for revision of custom-made tumor prosthesis of knee joint were mechanical problems and deep infection. Although revision surgery of knee is relatively compl icated and has some compl ications, a functional l imb could be maintained in most tumor patients.
Objective To achieve threedimensional (3D) contour image of boneand articular cartilage for fabricating custommade artificial semiknee joint as segment bone allograft.Methods The distal femora of human and pig were scanned with Picker 6000 spiral X-ray computed tomography with 1.0 mm thick slice. The data obtained were treated in Voxel Q image workstation for 3D reconstruction with volume rendering technique. After being downloaded to personal computer at 0.1 mm interval, the transaxial 2D image data were converted into 2D digitized contour data by using image processing software developed by the team. The 2D digitized data were inputted into image processing software of Surfacer 9.0 (Imageware Company, USA), then the 3D wire frame and solidimages of femoral condyle were reconstructed. Subsequently， based on the clinical experience and the requirement of the design of artificial knee joint, the 3Dcontour image of bone or articular cartilage was extracted from the surrounding.Results The 3D contour image of bone or articular cartilage presented was edited and processed easily for the computer aided design(CAD) of custom-madeartificial knee joint.Conclusion The 3D contour image of boneand articular cartilage can be obtained by spiral CT scanning, and the digitized data can beapplied directly to CAD of custom-made artificial joint and subsequently rapidprototyping fabricating. In addition, the reconstruction method is simple and can be applied widely to clinical implant fabricating practice of dentistry and orthopaedics.
Objective To design a new custom-made artificial semi-knee joint based on rapid prototyping(RP) technique and to explore a method to solve necroses of allocartilage in hemi-joint allotransplantation. Methods Based on the extracted 3D contour image of the articular cartilage of femoral condyle, the custom-made artificial semi-knee joint was designed with Surfacer 9.0 image processingsoftware. The artificial semi-knee joint design used the femoral condylar 3D contour of the patient as the outer face and the subchondral bone 3D contour of allograft bone as inner face. One dado for medullary nailand two for special designing cages which were used to fix the cartilage into the allograft were added on the inner face. After being converted into RP data format, the computerassisted design was imported into the LPS600 rapid prototyping machine, and the prototype was achieved. Furthermore, the prototype could be modified by hand according to the design. Then the RP model was used as a positive mould to build up a silica gel negativemould, and the negative mould was sent to the factory to manufacture Ti-6Al-4V alloy articular cartilage through ordinary mould-melted founding process. Finally, the whole metal cartilage was completed after melting two special cages on it andpolishing it. Results A new custom-made artificial semi-knee joint was made ad used to treat a 14-year old patient. The custom-made artificial semi-knee joint and the subchondral bone were a perfect match. The operative result was satisfactory. The patient could walk 5 weeks after operation. The bone healing of the auto-bone and allo-bone was achieved 6 months later. A follow-up period lasting 1 yearshowed that the knee joint played a good function. Conclusion The artificial semi-knee joint is a good match for the allograft boneand a good idea to solve necroses of allocartilage in hemijoint allotransplantation.