The clinical and radiographic impact of center of rotation lateralization in reverse shoulder arthroplasty: a systematic review

Reverse shoulder arthroplasty (RSA) has been widely adopted in the United States since its approval by the United States Food and Drug Administration in 2003. Advancements in metallurgy and design (including locking screws) have yielded clinically successful prostheses with a lateralized center of rotation (COR). This systematic review compared postsurgical outcomes and failure rates for lateral vs. medial COR RSA. We hypothesized that progressive lateralization of the COR results in greater ROM, improved clinical outcome scores, fewer acromial stress fractures, and less notching but a higher rate of glenoid implant baseplate failure and dislocation. PubMed, Embase, Web of Science, CINAHL, and Cochrane databases were searched from inception through June 7, 2017, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eighteen articles were included after final review. Studies were stratified on whether a prosthesis with a lateral or medial COR was used. Comparisons included shoulder range of motion (ROM), functional outcome scores, and reported complications. RSA demonstrated significant improvements in outcome scores postsurgery regardless of prosthesis type. Overall, this study found no clear difference in outcome scores between the lateralized and medialized COR groups. The lateralized COR group displayed increased postoperative ROM. There was a higher reported incidence of scapular notching with medial COR prostheses. Otherwise, there were no clear differences in complications between the 2 groups. The data suggest no significant differences exist between groups in outcome scores. The lateralized COR prosthesis showed increased postoperative external rotation and decreased scapular notching. Additional well-constructed randomized controlled trials would allow more effective comparison of these prosthesis designs.