Titanium nitride ceramic film against polyethylene. A 48 million cycle wear test.

Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce > 40 million motion cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37 degrees C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was < 0.02 mm, and < 2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.