2008 John Charnley award: metal ion levels after metal-on-metal total hip arthroplasty: a randomized trial.
Metal-on-metal bearing total hip arthroplasty is performed more commonly than in the past. There may be manufacturing differences such as clearance, roughness, metallurgy, and head size that affect performance. In a prospective, randomized trial, we compared 2-year postoperative ion levels for a 28-mm metal-on-polyethylene bearing with 28-mm and 36-mm metal-on-metal bearings. We measured serum, erythrocyte, and urine ion levels. We observed no difference in the ion levels for the 28-mm and 36-mm metal-on-metal bearings. The ion levels in these patients were lower than reported for most other metal-on-metal bearings. Although both erythrocyte and serum cobalt increased, erythrocyte chromium and erythrocyte titanium did not increase despite a four- to sixfold serum chromium and a three- to fourfold serum titanium increase. This may represent a threshold level for serum chromium and serum titanium below which erythrocytes are not affected.


METHODS
Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Anderson Orthopaedic Research Institute, Alexandria, VA 22307, USA.
C Anderson
CA
Engh
Steven J
SJ
MacDonald
Supatra
S
Sritulanondha
Abigail
A
Thompson
Douglas
D
Naudie
Charles A
CA
Engh
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D001363:Awards and Prizes; D002857:Chromium / Q000097:blood / Q000652:urine; D003035:Cobalt / Q000097:blood / Q000652:urine; D004912:Erythrocytes / Q000378:metabolism; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D008670:Metals / Q000097:blood* / Q000652:urine*; D008875:Middle Aged; D020959:Polyethylene; D011183:Postoperative Complications / Q000097:blood / Q000652:urine; D011446:Prospective Studies; D014025:Titanium / Q000097:blood / Q000652:urine
D008670:Metals; D002857:Chromium; D003035:Cobalt; D020959:Polyethylene; D014025:Titanium