The Shoulder Arthroplasty Smart Score Correlates Well With Legacy Outcome Scores Without a Ceiling Effect.

Abstract

The Shoulder Arthroplasty Smart (SAS) score is a new, validated machine learning-derived outcome measure that requires six input parameters. The SAS score has the potential to replace legacy shoulder outcome scores. We conducted a retrospective review of a multinational shoulder arthroplasty database of one platform shoulder prosthesis (used interchangeably for anatomic and reverse total shoulder arthroplasty). All primary shoulder arthroplasties with a minimum of two-year follow-up and an available SAS score were evaluated. Associations between scoring systems were assessed using Pearson correlations, with 95% confidence intervals stratified by time point (preoperatively and postoperatively at 2- and 5-year follow-ups, respectively) and procedure (anatomic verses reverse total shoulder arthroplasty). Conversion equations were developed using the best-fit line from linear regression analysis. Ceiling effects were assessed based on two definitions: (1) >15% of participants scoring the maximal possible score and (2) a standardized distance less than 1.0, whereby the standardized distance is calculated by subtracting the mean from the maximal score and dividing by the standard deviation. Two thousand four hundred six shoulders were evaluated at 4,553 clinical encounters. For preoperatively collected data, the SAS score correlated strongly with the Constant (R = 0.83), University of California at Los Angeles (R = 0.85), and Shoulder Pain and Disability Index (R = -0.70) scores and moderately with the American Shoulder and Elbow Surgeons (R = 0.69) and Simple Shoulder Test (R = 0.65) scores. The SAS score strongly correlated (R > 0.7) with all legacy outcome scores collected at 2- and 5-year postoperative visits. Score predictions made using the conversion equations between the SAS score and legacy outcome scores strongly correlated with their actual values. Neither the SAS nor the Constant score were influenced by ceiling effects. All other outcome scores evaluated demonstrated ceiling effects. The SAS score correlates well with legacy shoulder scores after primary shoulder arthroplasty while mitigating ceiling effects. Surgeons may decrease patient questionnaire burden by using the brief six-question SAS score.