A major cause of failure of a total joint arthroplasty (TJA) is due to w ear of the ultra-high molecular weight polyethylene bearing surface. To accelerate materials development, fundamental to prolonging TJA service life, advancements in m aterials testing techniques are essential. Improved materials screening tests, used early in the design process, are required.

A materials screening test was designed that produces high-stress, non conforming contact and executes an articulation involving cross shear as well as unidirectional and turning motion. A protocol for surface damage assessment was developed, involving multi-scale surface imaging, assessment of oxidation, and w ear debris isolation. The methodology was validated through testing of a conventional and a highly crosslinked ultra high molecular weight polyethylene for “wear-in”, testing to 50, 250 and 500 kilocycles.

Differences in wear performance of the two materials were detected. In addition, response to kinematic conditions varied in the two materials tested. This study highlights the utility of wear-screening machines, as well as the significance o f test conditions such as kinematics, and test duration. Wear investigations must be performed under controlled conditions to help elucidate the direct cause-and-effect of articular parameters. Observation of the wear surfaces must be done using a multi-scale approach, as similarities on one level of magnification do not preclude differences on another scale.