Predicting outstanding results after reverse shoulder arthroplasty using percentage of maximal outcome improvement

Abstract

The purpose of this study was to determine whether thresholds regarding the percentage of maximal improvement in the Simple Shoulder Test (SST) score and American Shoulder and Elbow Surgeons (ASES) score exist that predict excellentpatient satisfaction after reverse shoulder arthroplasty (RSA). Patients undergoing RSA with a single implant system were evaluated preoperatively and at a minimum 2-year follow-up. Receiver operating characteristic curve analysis determined thresholds to predict excellentpatient satisfaction by evaluating the percentage of maximal improvement for SST and ASES scores. Preoperative factors were analyzed as independent predictors for achieving SST and ASES score thresholds. There were 198 (SST score) and 196 (ASES score) patients who met inclusion criteria. For SST and ASES scores, receiver operating characteristic curve analysis identified 61.3% (P < .001) and 68.2% (P < .001) maximal improvement as the threshold for maximal predictability of excellentsatisfaction, respectively. Significant positive correlation between the percentage of maximum score achieved and excellentpatient satisfaction for both groups was found (r = 0.440[P < .001] for SST score; r = 0.417 [P < .001] for ASES score). Surgery on the dominant hand, greater baseline visual analog scale pain score, and cuff arthropathy were independent predictors for achieving the SST and ASES score threshold. Thresholds for the achievement of excellentsatisfaction after RSA were 61.3% of maximal SST score improvement and 68.3% of maximal ASES score improvement. Independent predictors of achieving these thresholds were dominant-sided surgery and higher baseline visual analog scale pain scores for the SSTscore and rotator cuff arthropathy for the ASES score.