BackgroundBoth anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA) are the standard of care for various end-stage degenerative conditions of the glenohumeral joint. The purpose of this prospective study was to compare clinical outcomes of aTSA and rTSA using the same platform total shoulder arthroplasty system at a minimum follow-up of 8 years. MethodsAn international multicenter data registry was used to identify patients undergoing primary aTSA or rTSA with a minimum of 8-year follow-up. Patients were scored preoperatively and at latest follow-up using 6 outcome and 4 range of motion metrics. Patients graded global shoulder function on a 0-10 scale. Patient satisfaction was classified as much better, better, unchanged, or worse. Pain was graded using the Visual Analog Scale. A student’s 2-tailed paired t-test, Chi-squared test, or Wilcoxon rank-sum test were used when appropriate, where P < .05 indicates significant differences. ResultsA total of 364 aTSA patients and 278 rTSA patients were included. rTSA had greater mean age (aTSA 65.1, rTSA 71.2, P < .0001) and shorter mean follow-up (aTSA 115.2 months, rTSA 109.7 months; P = .0002). Postoperatively, all patients demonstrated significant improvements in pain and function. Preoperatively, aTSA patients had greater active abduction and forward elevation, global function, Constant Score, and the University of California, Los Angeles score. At latest follow-up, aTSA had greater active abduction, forward elevation, external rotation, and Simple Shoulder Test scores. There were no postoperative differences in patient satisfaction, shoulder function, pain, or any other outcome measure between the groups. aTSA patients had a greater revision rate (aTSA 5.8%, rTSA 1.8%; P = .0114), with no difference in complication rates. Humeral radiolucent lines were present in 20.9% of aTSA patients and 37.1% of rTSA patients (P = .0011). Glenoid radiolucent lines were present in 48.0% of aTSA patients (average score of 1.5). Scapular notching was present in 14.5% of rTSA patients (average grade of 0.26). ConclusionThis study is one of the largest to date that compares aTSA and rTSA with a minimum follow-up of 8 years. Significant improvements are seen in both aTSA and rTSA. For both groups, the complication rate was lower than previously reported in the literature. At the latest follow-up, pain relief and global function were significantly improved with high patient satisfaction in both groups, with no statistical differences found. This study provides physicians with information to help guide them when advising patients as to what they can expect at a minimum of 8 years after aTSA and rTSA.