[Fabrication of custom-made artificial semi-knee joint based on rapid prototyping technique: computer-assisted design...

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.

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 processing software. 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 nail and 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 computer-assisted 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 negative mould, and the negative mould was sent to the factory to manufacture Ti-6A1-4V alloy articular cartilage through ordinary mould-melted founding process. Finally, the whole metal cartilage was completed after melting two special cages on it and polishing it.

A new custom-made artificial semi-knee joint was made and 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 year showed that the knee joint played a good function.

The artificial semi-knee joint is a good match for the allograft bone and a good idea to solve necroses of allocartilage in hemi-joint allotransplantation.