Is the Simple Shoulder Test a valid outcome instrument for shoulder arthroplasty?

Abstract

The Simple Shoulder Test (SST) is a brief, inexpensive, and widely used patient-reported outcome tool, but it has not been rigorously evaluated for patients having shoulder arthroplasty. The goal of this study was to rigorously evaluate the validity of the SST for outcome assessment in shoulder arthroplasty using a systematic review of the literature and an analysis of its properties in a series of 408 surgical cases. SST scores, 36-Item Short Form Health Survey scores, and satisfaction scores were collected preoperatively and 2 years postoperatively. Responsiveness was assessed by comparing preoperative and 2-year postoperative scores. Criterion validity was determined by correlating the SST with the 36-Item Short Form Health Survey. Construct validity was tested through 5 clinical hypotheses regarding satisfaction, comorbidities, insurance status, previous failed surgery, and narcotic use. Scores after arthroplasty improved from 3.9 ± 2.8 to 10.2 ± 2.3 (P < .001). The change in SST correlated strongly with patient satisfaction (P < .001). The SST had large Cohen's d effect sizes and standardized response means. Criterion validity was supported by significant differences between satisfied and unsatisfied patients, those with more severe and less severe comorbidities, those with workers' compensation or Medicaid and other types of insurance, those with and without previous failed shoulder surgery, and those taking and those not taking narcotic pain medication before surgery (P < .005). These data combined with a systematic review of the literature demonstrate that the SST is a valid and responsive patient-reported outcome measure for assessing the outcomes of shoulder arthroplasty.