CT-Based Local Soft-Tissue Composition Does Not Predict Early Clinical Outcomes After Primary Elective Reverse Total Shoulder Arthroplasty

OBJECTIVES: CT-based measurements of local muscle and adipose tissue have demonstrated more reliable predictive ability for select clinical outcomes after anatomic (aTSA) and reverse total shoulder arthroplasty (rTSA) compared with body mass index (BMI). However, the optimal method for assessment has yet to be established. METHODS: A retrospective analysis of consecutive primary short-stem rTSA undertaken at a single institution was conducted. Patient demographic and surgical outcome data, including age, BMI, five-item Modified Fragility Index (mFI-5), surgical time, length of stay (LOS), surgical site soft-tissue and osseous complications, all-cause 90-day ED return, and 90-day readmission, were collected. Local adipose and deltoid muscle areas, in addition to proximal humeral bone area, at predetermined axial cuts were determined using open-source medical imaging software. Regression analysis was used to assess the correlations of BMI, adipose-to-muscle ratio (AMR), and soft tissue-to-bone ratio (SBR) with postoperative clinical outcomes. RESULTS: A total of 200 cases were included in this study. The mean age of the cohort was 70.9 ± 7.9 years. The median BMI was 31.0 (IQR 27.6, 34.4). BMI correlated with AMR and SBR (r = 0.501 and r = 0.432, respectively, P < 0.001). After regression analysis, AMR, SBR, and BMI were not significantly correlated with surgical time, the development of in-hospital medical complications, and 90-day all-cause ED return (P > 0.05). Having an ED visit within 12 months preoperatively (OR 6.83, 95% CI, 3.0-15.59, P < 0.001) was associated with a significantly increased risk of experiencing an all-cause 90-day ED return. Anxiety was associated with both in-hospital medical complications (OR 2.54, 95% CI, 1.06-6.09, P = 0.036) and 90-day medically related ED return (OR 2.62, 95% CI, 1.08-6.35, P = 0.034). CONCLUSION: These findings suggest that additional study into the influence of both local shoulder adiposity and overall body habitus is needed to better understand their effect on postoperative clinical outcomes.