Do we need to reconsider how we gauge success after anatomic total shoulder arthroplasty? A study of thresholds optimized for patient satisfaction using the Simple Shoulder Test.

BACKGROUND

Clinically important improvement after total shoulder arthroplasty is often assessed with shoulder-specific patient-reported outcome measures (PROMs) quantifying reduction in pain and restoration in function. It is unclear if commonly used thresholds such as minimal clinically important difference (MCID), substantial clinical benefit (SCB), or patient acceptable symptom state (PASS) represent optimal improvement from the patients' perspective. The objectives of this study were to use the Simple Shoulder Test (SST) to (1) compare commonly used thresholds for change in score and final score to thresholds optimized to patient satisfaction using receiver operating characteristic (ROC) curve analysis, and (2) determine the impact of using different thresholds on reporting of independent predictors of successful outcome in terms of patient satisfaction.

METHODS

This study included 406 anatomic total shoulder arthroplasty (aTSA) patients from a longitudinally maintained database with 2-year follow-up. Surveys included the SST and a satisfaction questionnaire. SST thresholds were calculated by commonly described techniques for MCID, SCB, %MPI (percentage of maximal possible improvement), and PASS. ROC curves were constructed to determine the optimal threshold of SST change in score (Change-ROC), final SST score (Final-ROC), and %MPI (%MPI-ROC) based on patient satisfaction. Youden index (J) was calculated to determine each threshold's performance in maximizing sensitivity and specificity. Multivariable analysis was performed to determine predictors of surpassing selected threshold values.

RESULTS

The thresholds with the highest Youden index correlating best with patient satisfaction were %MPI-ROC (aTSA, 61%, J = 0.49) and Final-ROC (aTSA, 9.5, J = 0.48). Commonly used thresholds including MCID of 2.0 (J = 0.21) and SCB of 2.7 (2.7) had the lowest Youden index of the thresholds studied. Characteristics predictive of success varied substantially according to the selected threshold.

CONCLUSIONS

Current thresholds commonly used to gauge success after aTSA have limited ability to predict success based on patient satisfaction using the SST. Given that focus in health care value is shifting toward patient satisfaction, optimal thresholds used to measure success after shoulder arthroplasty may require reconsideration.