The Effect Of Surgical Instrumentation On Interface Motion In Uncemented Hip Prostheses

The Effect of Surgical Instrumentation on Interface Motion in uncemented Hip prosthesesComparison of CASPAR -system and Convention-manual for Femoral Canal ofPrepareationDepartment of Surgery Medical School of ZheJiang University Ph.D Candidate Tao huiminTutor Yang disheng Peng shuyouMeasurement of micromotion , defined as small relative motion at the interface between bone and implant, can provide valuable comparative data with regard to initial stability. Initial stability at the interface between the prostheses and bone in femora that provides a potential mechanical stable environment for bone ingrowth in uncemented femoral components. Biological fixation or Ossess-integration by bone ingrowth into the prosthesis surface was testifed in vivo studies and history biospy of human femoral bone and implant composite, is generally thought to an important condition, achieve long-term fixation. The highter the initial stability of the implant at time of implanta-tion, the better is the stable ingrowth into the implant. So the important of improving initial stability is emphasised, hi the clinical investigation, Excessive motion at the interface between bone and implant affect bone ingrowth and remodeling, are believed to induce thigh pain, the high incidence of periprosthetic femoral osteolysis and ultim-ately lead to loosening of the implant. In the canine vivo study, Pilliar et al. found that micromotions of the interface is greater than ISOum will inhibit bone ingrowth and lead to fibrous encapsulation of the uncemented implant. Jasty and Harris demonstrated the in vivo patterns of bone ingrowth and remodeling are related with different magni-tudes of micromotion of poroused-coated implanteds. Soballe et al. also found the fibrocartilaginous tissue characterized the membrane around unstable HA(hydroxyapa-tite) implants.Thus the initial stability achieved by implant inserted without cement, will be affected some important factors, such as the improving of the surgery techniques and instrumentation, the design of the implant, the load of the implant postoperation, the quality of the femoral bone bed and the material of the implant. In the design principle of the implant, Fit and fill between the prostheses and bone in femora is prerequisite for achieving initial stability. However, many experimental and clincal studies forcus on how improved the design of the implant and the structure of the implant surface, to fit and fill for the different femoral canal geometries in the control of micromotion at the interface. On the other hand, operational technique and surgical instrumentation, as used to prepare femoral canal, plays an important role in initial fixation, is improved how to fit for the different design of the implanst better, is not still emphasised.The conventional surgery techniques and instrumentation that can not ensure initial accuracy contact between the prosthesis and bone. In order to achieve optima] initial fixation of the implant, robot-assisted (CASPAR) implantation of the cementless implant has been performed in orthopedical clinic in Kiel universtry since 1999. Preoperative planning and data from analysis of CTimage at a three-dimensional graphic work station, are transferred to the robot, which transforms the preoperative planning and date by milling the femoral cavity with the highest precision. The CASPAR -system is thought to be safe and effective- in producing radiographically superior implant fit and fill while eliminating femoral fractures.Postoperative followed-up results are satisfaction with achieving initial stability of the cementless implant.Few experimental studies have examined how prepared the femoral canal through CASPAR -system and Convention-manual affect micromotion of the femoral implant To measure the extent of these three-dimensional movements, an in vitro synthetic composite model femora method for measurement of the micromotion of the femoral component of hip prostheses in the same femoral condition has been developed. Com-pari...