Total shoulder arthroplasty, originally used by Pean in 1893 to treat tuberculous arthritis1 and subsequently modernized by Neer et al. in the 1950s for the treatment of three and four-part proximal humeral fractures2, has demonstrated clinical efficacy when used for the treatment of primary and secondary degenerative conditions of the shoulder. The overall number of shoulder replacements has increased in parallel to the total number of total joint arthroplasties. Approximately 7000 total shoulder replacements were performed annually in the United States from 1996 through 2002. This represents a 40% increase compared with the 5000 arthroplasties per year performed from 1990 through 19923-11. Despite the increase in the annual volume of shoulder arthroplasties, data have suggested that nearly three-fourths of the operations are performed by surgeons who do two or fewer procedures a year12,13. The favorability of the clinical outcomes of total shoulder arthroplasty as well as the decision to proceed with a total shoulder replacement instead of a hemiarthroplasty have been shown to depend on surgeon experience and hospital volume12-16. Patient readmission rates, complication rates, and lengths of hospital stays have all been shown to …