Primary Reverse Shoulder Arthroplasty Did Not Result in Increased Blood Metal Ion Levels Regardless of Glenosphere Size: A Randomized Controlled Trial

Abstract Background The utilization of reverse shoulder arthroplasty (RSA) has increased over time. Toxic increases of metal ion levels have been reported selectively after hip arthroplasty. However, studies evaluating the effect of RSA on in vivo metal ion levels have not been evaluated. Therefore, the purposes of this study were (1) to determine in vivo levels of cobalt, chromium, and nickel in a randomized controlled trial of patients undergoing reverse total shoulder arthroplasty (RSA) with one of four glenosphere sizes, and (2) to identify possible factors affecting changes in metal ion levels. Methods Between May 2016 and September 2018, 72 shoulders with cuff tear arthropathy, massive irreparable cuff tears, or glenohumeral osteoarthritis with posterior subluxation were randomized to undergo underwent RSA using a single implant system and four possible glenosphere options based on size (36 or 40mm) and offset (+2mm, +6mm). In vivo metal ion levels (cobalt, chromium, nickel) and complete blood count (CBC) were assessed preoperatively, 3-months, and 1-year after surgery. Clinical evaluation included pain, motion, Subjective Shoulder Value, ASES scores, and Oxford Shoulder Scores. Results Reverse shoulder arthroplasty led to statistically significant improvements in all outcome measures considered (p Conclusion In this randomized controlled trial of patients undergoing reverse total shoulder arthroplasty with a single design, in vivo levels of cobalt, chromium, and nickel remained reassuringly low. In addition, increase in glenosphere size, offset, or both, did not appear to affect in vivo metal ion levels over the short-term. Longer term studies are needed to further assess the effects of implant modularity on metal ion levels and their potential adverse effects in patients undergoing reverse shoulder arthroplasty. Level of evidence Level I; Randomized Controlled Trial