Urinary Excretion Levels of Metal Ions in Patients Undergoing Total Hip Replacement with a Porous-Coated Prosthesis: Preliminary Results

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Abstract
Porous-coated prostheses implanted without bone cement are currently being evaluated for use in patients undergoing total joint replacement (TJR). One parameter under study is the potential release of metal ions from these prostheses. In order to determine if there is a systemic increase in cobalt, chromium, or nickel levels within the body subsequent to total joint replacement with a porous-coated prosthesis, 24-h urine specimens were collected from patients prior to and subsequent to TJR with a PCA total hip prosthesis. Metal ion analysis was achieved using flameless atomic absorption spectroscopy. Increases in urinary cobalt and nickel excretion were detected in several patients at six months and in most patients at one year after surgery. However, these differences were not statistically significant. No differences between the preoperative and postoperative time periods (one week, six months, and twelve months) were detected for urinary levels of chromium. Although the metal ion levels for all of the patients studied appear to be in the range handled by the body's systemic compensatory mechanisms, which adjust levels of trace elements, continued follow-up is needed to determine the patterns and the long-term significance of metal ion release.
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