Based on success of hip resurfacing, large head Metal on Metal (MoM) hip arthroplasty has gained significant popularity in recent years. There are growing concerns about metal ions related soft tissue abnormalities. The aim of this study was to define a correlation of metal ions with various functional outcome scores following large head MoM hip arthroplasty. Consecutive cohort of 70 patients (76 hips) with large head MoM hip arthroplasty using SL-Plus femoral stem and Cormet acetabular component were prospectively followed up. An independent observer assessed the patients which included serology for metal ion levels and collection of Oxford Hip, Harris hip, WOMAC, SF-36 & modified UCLA scores. Median serum cobalt and chromium levels were 3.10？ g/L (0.35–62.92) and 4.21？ g/L (0.73–69.27) with total of median 7.30？ g/L (2.38–132.19). The median Oxford, Harris, WOMAC, SF-36 and modified UCLA scores were 36 (6–48), 87 (21–100), 36 (24–110), 104 (10–125), and 3 (1–9), respectively. Seventeen patients had elevated serum cobalt and chromium levels ≥7？ g/L. There was no significant correlation between serum metal ion levels with any of these outcome scores. We recommend extreme caution during follow up of these patients with large head MoM arthroplasty. 1. Introduction Following the success of hip resurfacing procedures, large head metal-on-metal hip (MoM) arthroplasty has become popular due to perceived advantages of low wear rate of metal-on-metal bearings and reduced dislocation rate of utilising large heads (≥36？mm). Midterm clinical results of such device have been encouraging [1–6]. Systemic effects of metal ions and wear debris of metal-on-metal bearings leading to necrotic and inflammatory local soft tissue reactions are cause of concern [7]. Medicine and Healthcare products Regulatory Agency (MHRA) issued alert on most MoM bearings suggesting continued surveillance of such device with regular clinical outcome, metal ion level measurement and cross-sectional imaging if required [8]. There is ongoing debate about safe level of metal ions, relation to soft tissue abnormality, and its use in screening for MoM-bearing device followup. De Smet et al. recommended that metal ion measurement should be used as diagnostic tool to identify problems with MoM hip resurfacing based on their work of revision surgery for metal-on-metal bearing device [9]. It is now understood wear characteristics of large head MoM hip implants are significantly different and higher than those of resurfacing implants [10–12]. There are outcome scores that are routinely used in all
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