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BackgroundAdverse soft tissue reactions in metal-on-metal (MoM) hip replacements are associated with cobalt (Co) and chromium (Cr) ions in blood. We report the prevalence and risk factors for elevated blood Co and Cr levels in patients with a unilateral MoM hip.MethodsFrom a single institution, blood Co and Cr levels were analyzed in 1748 patients (692 hip resurfacings and 1056 total hip arthroplasties [THAs]). Concentrations exceeding 7 ppb were considered elevated, and the risk factors for elevated levels were calculated with binary logistic regression.ResultsElevated blood metal ion levels were more common in MoM THA than in resurfacing patients (17.4% vs 5.9%, P < .001), and in 5 of the 7 THA brands, more than 20% of patients had elevated metal ion concentrations, whereas the proportion was less than 10% in all hip resurfacings. In resurfacings, small femoral head (odds ratio [OR] 1.30 per millimeter decrease [CI, 1.12-1.49]), high acetabular inclination (OR 1.15 per degree increase [CI 1.09-1.22]), and young age (OR 1.05 per year decrease [1.02-1.10]) were independent risk factors for elevated ions. In the THA group, female gender (OR 2.04 [CI 1.35-3.06]), longer time between surgery and ion measurement (OR 1.19 per year increase [CI 1.05-1.34]), and large headsize (OR 1.07 per millimeter increase [CI 1.01-1.13]) were risk factors for elevated ions.ConclusionGiven the high percentage of elevated levels, the systematic surveillance of especially large diameter MoM THAs seems justified.

Original publication

DOI

10.1016/j.arth.2015.11.045

Type

Journal article

Journal

The journal of arthroplasty

Publication Date

06/2016

Volume

31

Pages

1261 - 1266

Addresses

Coxa Hospital for Joint Replacement, Tampere, Finland.

Keywords

Humans, Ions, Chromium, Cobalt, Metals, Range of Motion, Articular, Arthroplasty, Replacement, Hip, Multivariate Analysis, Risk Factors, Hip Prosthesis, Adult, Aged, Middle Aged, Female, Male, Metal-on-Metal Joint Prostheses