The Design Of The Second Generation Customized Bipolar Hemi-knee Joint Prosthesis And The Related Study

According to the nature of bone tumors can be divided into both benign and malignant two kinds. The treatment of Benign bone tumors is generally in local area cut and internal fixation.however, Malignant bone tumors usually need to undertake widely or radical surgery that cause extensive bone defect, joint injury and failure, and even need amputation. The Children’s knee malignant bone tumors has long been the medical hot and difficult problem. Along with the wide application of neoadjuvant chemotherapy, not only improve the prognosis of malignant bone tumors survival, also makes limb-salvage reconstructive surgery become an important treatment instead of amputations means. Because of children and youths in high risk of affecting malignant bone tumors,The Limb-salvage reconstructive surgery should more notice the function recovery.At presant, the mechanical reconstruction methods(such as artificially prosthesis replacement) and biological reconstruction methods(such as tumor section bone inactivated and reconstruction) are feasible. Using artificially prosthesis replacement treating children knee malignant bone tumor is widespread and more generally. Because children and teenagers knee malignant bone tumors after traditional prosthesis implantation (simpleTKR, etc.) would cause the epiphysis damage and missing children, even more making the limb relatively slow growth, resulting in significantly limb shortening.When the malignant bone tumors located in metaphyseal and epiphyseal side, and confirmed intra-articular and contralateral is not affect the tumor, we can retain the epiphysis of contralateral relative bone.Thus can alleviate the limb shortening after limb prosthesis implantation. A hemi-knee prosthesis replacement is based on these concepts and used in children knee malignant bone tumor therapy. We successively proposed artificially hemi-knee prosthesis composite allograft limb-salvage treatment and bipolar hemi-knee prosthesis concept.The bipolar hemi-knee concept :we divided the knee action into two phases,the first phase is the prosthesis internal structure movement,which is assume daily frequent flexion 0°to 60°, Meanwhile the prosthesis is relative static to the tibial.when the knee’s flexion is beyond the frequent flexion range,the second phase is occured,during this time the prosthesis is rolling on the tibial platform. Based on this concept, in use CAD technology and RP technology, a first-generation bipolar hemi-knee prosthesis is produced. However ,the first generation bipolar hemi-knee prosthesis had some problem such as the low customized level and lacking of the ligament reattachment system,which causing poor prosthesis stability.We designed and produced the second-generation bipolar hemi-knee prosthesis by using engineering ,manufacturing and bionics technology. The second generation bipolar hemi-knee prosthesis retained the first generation’s principle and part features. The second generation bipolar hemi-knee prosthesis have only three parts (FPJP,FCCP and link-axis),which made a simple assembly and a simple structure characteristic.Customized by increasing range of the femoral condyles design ,high bionic level and has patellar slide design, The second generation bipolar hemi-knee prosthesis is more accords with human physiological structure. An effective ligament attachment system can maintain short-term and long-term stability after prosthesis installation.Due to the particularity of new ligament attachment system,we did some exploratory experiments such as the selection of ligament reattachment points and initial installation of the prosthesis. Use resin model on the attachment ligament prosthesis simulated ligament attachment. the results show that the attachment in 105°Angle for the initial installation flexion, both fixed Angle reached larger flexion Angle, and closer to the physiological condition of standard human, this is the best initial installation Angle to second generation customization prosthesis.We used FEA to analysis the FPJP and intramedullary needle. Using the finite element analysis software ANSYS 11.0 software in the setup and Pro/Engineering 4.0 seamless connection interface, direct realization of CAD and CAE file conversion, has received the good effect.Selecting the SOLID92 and Femoral - tibial articular compression force in walking for maximum load weight loading the phase four times. We found that when the spindle intramedullary needle design, intramedullary handle length is 70mm, intramedullary handle Angle for 6.0°biomechanics distribution to more reasonable and realize optimization design.Recently, we used CAD technology and RP technology to produce a second generation customization prosthesis,and carry on the case of clinical trials. A female child patients,who caused right femur malignant schwannomas after 3 years, tumor section resection and allograft allografts postoperative produce pathologic fracture to the hospital for treatment. By obtained the patient’s family agreement, after meticulous discussion and medical argument, we used the second generation customization prosthesis to treat this child.and we gained definite effect, the follow-up shows the limb restore good, the child already restored some walk function.The bipolar hemi-knee concept is a new concept; New ligament attachment system is to solve the poor stability of the hemi-knee; Finite element results show that the rationality of the knee joint design structure; Clinical trials further shows the bipolar hemi-knee prosthesis the feasibility and effectiveness to the patient. The bipolar hemi-knee concept puts forward a new way that can solve the children malignant bone tumors limb-salvage treatment,and it has very important practical significance.