Sunday, August 25, 2013

Interesting study on the rapidity of decline of Cr and Co level after metal bearings are removed.

2013 Aug 12. pii: S0883-5403(13)00505-6. doi: 10.1016/j.arth.2013.06.040. [Epub ahead of print]

What Happens to Serum Metal Ion Levels After a Metal-on-Metal Bearing is Removed?

Source

Department of Orthopaedic Surgery, University of California, San Diego, California.

Abstract

Serum cobalt (Co) and chromium (Cr) levels are commonly used to screen for excessive wear of metal-on-metal hip replacements. However, it is unknown how rapidly these should decline after revision. 25 patients with average Co and Cr ion levels of 56.3μg/L and 20.5μg/L were followed with serial ion level testing post-revision. Over the first 6weeks post-revision, the rate of decline for Co and Cr was approximately 2% per day and this slowed to approximately 1% decline per day over the ensuing 6weeks. This translated to a decline of approximately 80% from the starting value after 6weeks and a decline of approximately 90% after 12weeks post-revision. The rate of decline for both Co and Cr was significantly faster during the first 6weeks (P<0.001). In patients with ultra-high Cr levels>20μg/L, the rate of Cr decline is less predictable and may be protracted leading to persistent elevation above 5μg/L for one year or more post-revision in some cases.

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