A New Custom-made Artificial Hemi-Knee Joint By Rapid Prototyping

The limb salvage was thriving with the development of neo-adjuent chemtherpay and surgical reconstruction and radiology.It is still a difficult problem for limb salvage of children. The massive allograft has been widely used ,but osteoarthritis caused by mismatch between allograft cartilage and opposite cartilage is difficult to solve .It is become more and more importment with the surge of survivorship.This research is based on the excellent result of massive allograft therapy carried out by the department of orthopaedic of Xijing hospital, aiming at the necrosis of the allograft cartilages. With the knowledge of modem computer and engineering,the study designed and manufactured a new custom-made hemi-knee joint and explored the procession by animal test and clinical trial:a.Duplicating the shape of joint surface by the CT images of knee joint . b.Integration the shape of inner and outer surface of patient's femur condyle and allograft's. c.The prothesis was planted with intramedullary nail which was designed before ,combined with massive allograft.What has done above was to preserve epiphysis of tibia,to reduce the possibility of osteoarthritis, to get biological reconstruction after resection of bone tumor and good function of kneejoint after operation.The research group has set up the project of custom-made hemi-knee joint by "CT/RP/QC";brought out the quick method of custom-made hemi-knee joint by "Mimics&ImageManager/Surfacer/UG".The recycle of manufacture was reduced by new craft .A general target device was devised to meet with the demand of operation and it proved well in animal test and clinical trial.The design,manufacture and clinical project were improved again and again ,and then the prosthesis was implanted into the pig and dog.The results showed the prothesis was press-fitted with the allograft subcartilaginous bone,and the joint space still existed.The function of knee joint was good.With the permission of related law ,the prothesis was implanted into a-fourteen-year-old boy who has got osteosarcoma in the distal right femur,combined with massive allograft bone.The results showed the prothesis and target device conformed with the demand of the design which was manufactured by RP.After 18 months follow-up postoperation, X-ray showed no deformation, loosening and breakage of prothesis. The joint space still existed with good internal fixation. The range of knee movement was from 0皌o 135?(actively and passively) with normal gait and good stability.The length of right limb is shorter than that of left lightly 1 year after operation.To deal with the problem of cartilage wear in animal test and clinical trial.and with the help of the idea of "bipolar"in the artifical femoral head replacement ,the research group bring out the idea of "bitrack" during the design of custom-made hemi-knee joint. Exploration is under way.