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.
Aiming at comparing the pre-operative and post-operative gait characteristics and therefore establishing post-operative rehabilitation guidance for patients with end-stage knee osteoarthritis (KOA) merged with varus deformity, this study captured the level walking and sit-to-stand trials of 9 patients with 3-dimensional motion analysis system and after which musculoskeletal multi-body dynamic analysis was conducted. The study indicated that the average range of motion (ROM) of the proposed-surgical knee was 24.4°–57.6° and that of the non-surgical knee was 22.5°–71.5°. The knee ROM of control group during level walking was 7.2°–62.4°. When the unilateral KOA patients stood up from chair to complete the sit-to-stand movement, the ground reaction forces (GRFs) symmetry was 0.72–0.85, which means that the non-surgical limb bear the majority of body weight. The GRFs of the bilateral KOA patients were smallest during the sit-to-stand movement. The strategy that the non-surgical limb dominates in loading bearing taken by the unilateral KOA patients to cover most post-operative daily activities could increase the risk of KOA among non-surgical side joints as a result of long-term excessive loading-bearing. The study, on kinematics and biomechanical characteristics of patients with KOA merged with varus deformity, could help to understand the pathogenesis of KOA merged with varus deformity from the perspective of biomechanics and to provide strong clinic guidance for the pre-operative evaluation, prevention and post-operative recovery for patients.