METALLIC WEAR DEBRIS IN METAL-BACKED PATELLAR FAILURE

Eight patients with failure of metal-backed patellar components were s tudied for evidence of intraarticular and systemic metal deposition. S even of the eight patients had failure of a titanium-based patellar co mponent that then articulated with a cobalt-chromium femoral component . One patient had articulation of a cobalt-chromium patellar component against a cobalt-chromium femoral component. All components failed by the same pattern of failure. Wearing of the ultra high molecular weig ht polyethylene was followed by displacement of the polyethylene and t hen metal-to-metal contact of the components. Methods for analysis of the debris included light and electron microscopy of synovial tissue a nd electron dispersive x-ray analysis (EDAX) of tissue. Graphite furna ce atomic absorption spectroscopy (GFAAS) was done on synovial fluid a nd synovial tissue as well as urine and blood specimens taken at vario us times from implantation to patellar revision. Massive deposition of metallic debris within the knee joint was documented both histologica lly and by GFAAS. Titanium levels reached as high as 2776 ppm (mg/L) i n the synovial fluid and as high as 917 mg/g of synovial tissue. Eleva tion of all the pertinent metals was seen in the tissue and body fluid s. Titanium and aluminum levels were the highest. Titanium levels in t he serum generally were highest near the time of implant failure. Othe r metal elevations were variable and could not be related to the time of failure. Synovial fluid levels of all metals and serum levels of ti tanium are reflective of intraarticular generation of metallic debris. This study demonstrates that in situations of failure of a device, ma ssive intraarticular debris generation occurs and systemic transport w ill occur. To date no systemic consequences can be attributed to the d eposition of debris and follow-up urine and blood specimens suggest th at debridement and revision of the failed device results in lowering o f the ion levels. (C) 1994 John Wiley and Sons, Inc.