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Mean chromium ion levels were significantly increased in patients with failed TKR
Savarino L. J Bone Joint Surg Br. doi:10.1302/0301-620X.92B5.23452.
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Measuring the serum level of chromium ions may be a new tool for detecting total knee implant loosening, according to Italian researchers.
Measurements of serum aluminium, titanium and cobalt ion levels had no diagnostic value, the researchers noted.
Lucia Savarino, BSc, Laboratory for Orthopaedic Pathophysiology and Regenerative Medicine Istituto Ortopedico Rizzoli, Bologna, Italy, and colleagues studied what role ion release plays in the assessment of total knee replacement (TKR) implant fixation.
The researchers enrolled 59 patients who underwent unilateral surgeries. They measured their serum aluminum, titanium, chromium and cobalt ion levels. The researchers were blinded to the clinical and radiological outcome, which was considered to be the reference standard.
To determine the detection cut-off levels, the researchers measured the ion levels in 41 healthy blood donors who did not have implants. The patients were then divided into two groups — stable (n=24) or loosened (n=35) implants — based on clinical and radiological evaluation.
The mean level of chromium (Cr) ions increased significantly in patients with failed implants (P=.001). “The diagnostic accuracy was 71%, providing strong evidence of failure when the level of Cr ions exceeded the cut-off value,” the authors wrote.
The researchers were able to distinguish loosening from other failure causes; when they considered only patients with failure attributable to loosening, the diagnostic accuracy reached 83%.