Wear of ultra high molecular weight polyethylene (UHMWPE) in total joint arthroplasties causes release of particulate debris that contributes to long term complications such as osteolysis and implant loosening (Wright and Goodman, 1996). Despite the magnitude of this clinical problem, little is known about wear mechanisms in UHMWPE implant components and the factors that control them. Total knee replacement designs, for example, require non-conforming metallic on UHMWPE joint surfaces to assure appropriate kinematics and function. Finite element analysis (FEA) has shown that contact between such surfaces leads to high surface and subsurface stresses (Bartel, et al., 1986). Dynamic FEA has also that shown that femoral rollback on the tibia results in considerable residual stresses in the polyethylene (Estupiñán, et al., 1996). In an effort to complement our analytical studies of stresses associated with wear damage, we have developed a wear apparatus. Our objective is to independently control factors including geometry of the joint surfaces, contact load, the presence (sliding) or absence (rolling) of surface velocity, and the polyethylene material properties, so as to experimentally examine their effects on the creation of damage similar to that observed on retrieved joint implants.

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