MRI-Based Shoulder Osteoarthritis Severity score (SOAS) is predictive of functional improvement following total shoulder arthroplasty

BackgroundTotal shoulder arthroplasty (TSA) is an increasingly common treatment for end-stage glenohumeral osteoarthritis. Current established radiographic measures and classification systems do not predict patient-reported outcomes from TSA. We hypothesized that the MRI-based Shoulder Osteoarthritis Severity (SOAS) Score would correlate with subjective improvement following TSA.MethodsPatients undergoing TSA with preoperative shoulder MRIs and pre- and postoperative ASES scores with minimum 2-year follow-up were included from a prospectively collected institutional shoulder arthroplasty database. SOAS scores, which is measured from 0 to 100 with an increasing score reflecting greater global degenerative changes, were assessed by two independent reviewers, and Samilson-Prieto grade and Walch classification were scored by one reviewer. Average SOAS scores were correlated with demographic factors and pre-, post-, and change (Δ) in ASES scores. Statistical analysis was performed with STATA with Pearson's correlation, one-way ANOVA, and ROC analysis, with significance defined by p <.05.Results30 patients (age 63 ± 10 years, 14 females, 16 males) who underwent primary anatomic TSA were included. The intraclass correlation coefficient (ICC) for total SOAS scores calculated by reviewers was 0.91. SOAS score correlated significantly with ΔASES (r = 0.61, p = .0003) and preoperative ASES (r = -0.37, p = .042), with greater MRI-based degenerative change associated with greater improvement after TSA and lower preoperative ASES score. No significant relationship was found between either Samilson-Prieto or Walch classification and SOAS or ASES scores. No significant relationship was found between SOAS scores and age, sex, or BMI. Using an MCID of 21 as previously reported, an ROC curve was generated and found to have an AUC of 0.96. A SOAS score cut-point of 36.25 was found to maximize sensitivity and specificity in predicting reaching MCID.ConclusionWe observed a significant positive correlation between the MRI-based SOAS score and functional improvement following TSA measured using change in ASES scores, indicating that patients with more advanced degenerative changes on MRI had greater improvement after shoulder replacement surgery. We found that the correlation strength was highest when comparing total SOAS score to ΔASES as opposed to any individual sub-component of the SOAS score. The MRI-based SOAS score for shoulder osteoarthritis may be a valuable tool for predicting patient outcomes following TSA.Level of evidenceLevel III; Retrospective Cohort Comparison; Prognosis Study