Designing And Manufacturing Study On Custom-made Artificial Cartilages Of Femoral Condyles For Massive Allograft

In the past 100 years the traditional therapy of bone tumor was amputation, only in the recent 20 years the limb salvage operation was thriving. The salvage operation is not a formulated operation, there are three methods: 1. prosthesis, 2. massive bone allograft. 3. replanting the tumor bone after some treatments. The three methods have different advantages and disadvantages: the prosthesis is accompanied with prosthesis loosing and the issue of the musculature fixation hasn't solved. The massive allograft and tumor bone replanting are accompanied with the necrosis of allograft cartilages. This experiment is based on the excellent result of massive allograft therapy carried out by the orthopaedic department of Xijing hospital, aiming at the necrosis of the allograft cartilages.The study designed and manufactured a new custom-made artificial cartilage of femoral condyle and explored the procession by a pig femur.The artificial cartilage has some advantages: 1. there are two cages in the inner face to fix the prosthesis, the cages should be full with allograft bone granules in operation. 2. the prosthesis use the cartilaginous contour of patient femur as the outer face and use the subcartilaginous bone contour of the allograft femur as inner face. 3. the prosthesis is connected with the intramedullary nail. 4. custom-made design. This design can press-lit with the tibial cartilage well, can avoid the osteoarthritis caused by allofgraft cartilage necrosis and can preserve the tibial epiphysis by unilateral replacement.The study uses the pig as the experimental subject to explore the process. A distal femur of a pig was scanned with Picker 6000 SCT with 1.0 slice thickness and pitch of 1.5, and the data obtained were treated in Voxel Q image workstation for 3D reconstruction with volume rendering technique. After having been downloaded to personal computer at O.lmm interval, the transaxial 2D image data were converted into 2D digitized contour data by using image processing software developed by experimental team. The 3-D wire frame and solid images of femoral condyle could be reconstructed when the digitized datawere inputted into image processing software of Surfacer 9.0. Subsequently based on the clinical experience and need of the design, the 3D contour image of articular cartilage was extracted from the surrounding.Using the extracted contours, The custom-made artifical cartilage of femoral condvle is CAD in Surfacer, the artifical cartilage design uses the femoral condylar 3D contour of patient as the outer face and the subchondral bone 3D contour of allograft bone as inner face, a dado for intramedullary nail and two for special designing cages which are use to fix the cartilage into the allograft are added on the inner face. After being converted into RP data format, the CAD design is imported into the LPS600 rapid prototyping machine (Hengtong Company, Xi'an Jiaotong University, China), and the prototype is achieved. Furthermore, the prototype can be modified by hand according to the design. Then the RP model is used as a positive mould to build up a silica gel negative mould, the negative mould is sent to the factory to manufacture Ti-6Al-4V alloy articular cartilage through ordinary mould-melted founding process. Finally, the whole metal cartilage is completed after melting two special cages on it and being polished.Finally, the prosthesis is implanted into the experimental pig and found out that the custom-made artificial cartilage has a excellent result. The artificial cartilage is press-fitted with the allograft subcartilaginous bone and fitted with the tibial articular cartilage very well.The study designed and manufactured the new custom-made artificial cartilages of femoral condyles based on the rapid prototyping technique which can meet with the new prosthesis' demand of diversity, complexity and rapidness. By the study of the custom-made artificial cartilage, we explored a process of custom-made implant based on rapid prototyping and made some groundwork for rapid, custom-...