The minimal clinically important differences of the Simple Shoulder Test are different for different arthroplasty types

Preoperative and postoperative patient self-reported measures are the key to understanding the benefit of shoulder arthroplasty for patients with different diagnoses and having different surgical approaches. The minimal clinically important difference (MCID) for patient-reported outcomes such as the Simple Shoulder Test (SST) is often used to document the amount of improvement that is of importance to the patient; however, the MCID may differ for different types of shoulder arthroplasty. The objective of this study was to report the MCID of the SST and the MCID of the percentage of maximal possible improvement (%MPI) for 5 different arthroplasty types.Eight hundred eighty-seven patients undergoing shoulder arthroplasty with preoperative SST scores, 2-year postoperative SST scores, and patient satisfaction were included. The sample comprised 368 patients undergoing anatomic total shoulder arthroplasty (aTSA), 330 patients undergoing ream-and-run arthroplasty (RR), 80 patients undergoing reverse total shoulder arthroplasty (rTSA), 53 patients undergoing cuff tear arthropathy arthroplasty, and 56 patients undergoing hemiarthroplasty. For each type of arthroplasty, the anchor-based method was used for calculating the MCID for both absolute SST scores and %MPI.Significant improvements in SST values were seen for all arthroplasty types. The MCID for SST change was 2.3 overall but ranged from 1.6 for aTSA, to 2.6 for RR, to 3.7 for rTSA. The MCID for %MPI was 32% overall but ranged from 22% for aTSA to 42% for hemiarthroplasty. The percentage of patients exceeding the MCID threshold was highest for aTSA at 96% and lowest for hemiarthroplasty at 61%.The same MCID value may not be appropriate for different types of shoulder arthroplasty. This study reports MCID thresholds that can be used when assessing the effectiveness for each of the common types of shoulder arthroplasty.