What happens to serum metal ion levels after a metal-on-metal bearing is removed?
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 56.3 μg/L and 20.5 μg/L were followed with serial ion level testing post-revision. Over the first 6 weeks 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 6 weeks. This translated to a decline of approximately 80% from the starting value after 6 weeks and a decline of approximately 90% after 12 weeks post-revision. The rate of decline for both Co and Cr was significantly faster during the first 6 weeks (P<0.001). In patients with ultra-high Cr levels>20 μg/L, the rate of Cr decline is less predictable and may be protracted leading to persistent elevation above 5 μg/L for one year or more post-revision in some cases.
Department of Orthopaedic Surgery, University of California, San Diego, California.
Scott T
ST
Ball
Dustyn
D
Severns
Michael
M
Linn
R Scott
RS
Meyer
F Craig
FC
Swenson
D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D020878:Device Removal; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D011474:Prosthesis Design; D012086:Reoperation; D013997:Time Factors
D008670:Metals; D002857:Chromium; D003035:Cobalt
chromium; cobalt; metal ions; metal-on-metal; revision total hip