Wear and survival of total joint replacements do not depend on the duration of the implant in situ, but rather on the amount of its use, i.e. the patient's activity level [1]. With this in mind, the present study was driven by two questions: (1) How does total knee replacement (TKR) respond to the simulation of daily highly demanding activities? (2) How does implant size affect wear response of total knee replacement (TKR)? Two sets of the same total knee prosthesis (TKP), different in size (#2 and #6), equal in design, were tested on a three-plus-one knee joint simulator for two million cycles using a highly demanding daily load waveform [2], replicating a stair-climbing movement. The results were compared with two sets of TKP previously tested with the ISO level walking task. Gravimetric and micro-Raman spectroscopic analyses were carried out on the polyethylene inserts. Visual comparison with in vivo explants was carried out and digital microscopy was used to characterize the superficial structure of all the TKPs and explanted components.Introduction
Materials & Methods
Total knee arthroplasty (TKA) is a consolidated orthopaedic procedure and success of such operation depends on the prosthetic design [1]. Unfortunately, as there is a good survival rate of primary TKA, failures occur for factors concerning the polyethylene composition of the implants, secondary osteolysis, and ultimately loosening of the implants are the usual causes of failure after normal use [2]. Dynamic Four commercial posterior-stabilized fixed-bearing component prosthesis for TKA were tested in this study (Stryker®-Orthopaedics, Mahwah, NJ-USA). These were new and delivered in sterilized packages. Particularly, corresponding UHMWPE tibial inserts (size #7) were made of conventional surgical grade polyethylene resin (GURâ�¨1020), consolidated by compression moulding (accordingly to ISO 5834/1-2), and EtO sterilized. These were tested in conjunction with corresponding CoCrMo alloy femoral components. For the implementation of realistic loading scenarios during in vitro wear testing for human joint prostheses, an in vitro protocol was designed to simulate the flexion/extension angle, intra/extra rotation angle, and antero/posterior translation. These movements were obtained in patients by three- dimensional video-fluoroscopy. Axial load data were collected by gait analysis [3].Introduction
Materials & Methods
