Correlation between serum metal ion levels and adverse local tissue reactions after Conserve® Plus hip resurfacing arthroplasty.

BACKGROUND: Adverse local tissue reactions (ALTR) have been associated with the use of metal-on-metal (MoM) bearings and the monitoring of cobalt (Co) and chromium (Cr) ion levels in blood or serum may be the best way to evaluate in vivo the wear of these bearings. However, the relationship between Co and Cr ion concentrations and the formation of ALTR remains unclear.

METHODS: We investigated the relationship between ALTR and serum Co and Cr ion levels and identified the clinical factors influencing the formation of ALTR in patients treated with MoM hip resurfacing arthroplasties. 228 patients with unilateral Conserve® Plus MoM hip resurfacing had serum metal ion studies performed more than 1 year after surgery. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) was performed on subjects at risk for ALTR as determined by a screening protocol.

RESULTS: 12 patients had ALTR. Logistic regression showed a strong association of ALTR with elevated ion levels and with low (<10 mm) contact patch to rim distance.

CONCLUSIONS: MoM bearings require enough functional coverage of the socket by design and then precise implantation to maximise functional coverage of the femoral ball, enhance lubrication, and avoid edge-loading wear.