ABSTRACT
A pneumatic simulator of the knee joint with five DOF was developed to determine the correlation between the kinematics of the knee joint, and the wear of the polyethylene componenent of a TKR prosthesis. A physical model of the knee joint with total knee replacement (TKR) was built by rapid-prototyping based on CT images from a patient. A clinically-available prosthesis was mounted on the knee model. Using a video analysis system, and two force and contact pressure plates, the kinematics and kinetics data were recorded during normal walking of the patient. The quadriceps muscle force during movement was computed using the Anybody software. Joint loadings were generated by the simulator based on recorded and computed data. Using the video analysis system, the precise kinematics of the artificial joint from the simulator was recorded and used as input for an explicit dynamics FE analysis of the joint. The distribution of the contact stresses in the implant was computed during the walking cycle to analyze the prosthesis behavior. The results suggest that the combination of axial loading and anterior-posterior stress is responsible for the abrasive wear of the polyethylene component of the prosthesis.
Subject(s)
Arthroplasty, Replacement, Knee/instrumentation , Biomimetic Materials , Imaging, Three-Dimensional/methods , Knee Joint/physiopathology , Knee Joint/surgery , Models, Biological , Surgery, Computer-Assisted/methods , Arthroplasty, Replacement, Knee/methods , Computer Simulation , Equipment Design , Equipment Failure Analysis , Finite Element Analysis , HumansABSTRACT
The paper presents the results of some comparative experimental studies that show the biomechanical changes which appear following different types of corrective osteotomy. The photoelastic technique was applied to plane models. The modifications in the stress distribution on the contour after the osteotomy in comparison with the situation before surgery were studied. Three types of osteotomy are considered: valgus osteotomy, varus osteotomy and Chiari pelvis osteotomy. Using the same experimental technique, the distribution of the contact pressure at the interface between the polyethylene cup and the femoral head is investigated, for a total hip prosthesis, as the extreme solution in the case of advanced hip arthroses. Both a normal situation and the malposition of prosthetic components were analyzed.