Red Cell Distribution Width as a Novel Predictor of Mortality and Complications After Primary Shoulder Arthroplasty.

INTRODUCTION: Variability in red blood cell volume can occur in disease states and is quantified using a simple equation, yielding the relative distribution of width (RDW). Recent literature has correlated RDW with outcomes in many cardiac disease states, hip fractures, and even revision hip arthroplasty. The association with outcomes in total shoulder arthroplasty (TSA) is yet to be delineated. The purpose of this study was to investigate the possible relationship between preoperative RDW levels and mortality and other adverse outcomes after primary TSA. METHODS: Patients who underwent primary TSA and had RDW values on record were identified in a national database. Patients were then grouped by RDW, and the incidence of complications was calculated for each group, including mortality within 1 year, periprosthetic infection within 1 year, acute venous thromboembolism within 30 days, and readmission to a hospital within 30 days. A threshold value of RDW for increased complications was established using receiver operator characteristic (ROC) curves. RESULTS: Five thousand two hundred forty-five patients who underwent TSA with a recorded RDW were included in the study. An RDW cutoff of 16% was found to be significantly associated with mortality at 1 year (P < 0.0001), readmission (P < 0.0001), and infection (P = 0.013) on ROC analysis. When controlling for demographic and comorbidity values, a high RDW was markedly associated with a higher mortality rate (odds ratio 2.0, 95% confidence interval 18 to 2.2) and readmission rate (odds ratio 1.5, 95% confidence interval 1.3 to 1.8). A high RDW was not markedly associated with increased infection or venous thromboembolism rate in the multivariate analysis. DISCUSSION: Increasing preoperative RDW is associated with increasing complication rates after TSA. This value can be used as an indirect, real-time preoperative predictor of adverse outcomes and most importantly one-year mortality and hospital readmission. LEVEL OF EVIDENCE: III retrospective cohort study.