Are Metal Ion Levels a Useful Trigger for Surgical Intervention?

OrthoCarolina Hip and Knee Center, Charlotte, North Carolina 28207, USA.
The Journal of arthroplasty (Impact Factor: 2.67). 05/2012; 27(8 Suppl):32-6. DOI: 10.1016/j.arth.2012.03.020
Source: PubMed

ABSTRACT The purpose of this study was to determine if cobalt and chromium ion levels can predict soft tissue damage at total hip revision. This study included 90 metal-on-metal total hip patients with preoperative cobalt and chromium ion levels. Tissue damage noted at revision surgery was graded on a 4-point scale. Sensitivity, specificity, and predictive values were calculated for various threshold values. Receiver operating characteristic analysis was conducted. Using 7 ppb as a threshold, cobalt and chromium ion levels had poor sensitivity and specificity (Co, 65% and 56%; Cr, 29% and 75%). Positive predictive values for cobalt and chromium were only 48% and 26% respectively. The area under the curve was 0.37 for cobalt and 0.44 for chromium. The length of time to revision significantly correlated with tissue damage (P = .001). Ion levels are unreliable predictors of periarticular soft tissue damage and should not be used in isolation as surgical intervention triggers.

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