Investigating the International Normalized Ratio Thresholds for Complication in Shoulder Arthroplasty

Background: In patients on warfarin anticoagulation therapy, elective shoulder arthroplasty surgeons must carefully balance bleeding and embolic risks. Currently, an international normalized ratio (INR) threshold of 1.5 is supported in the setting of elective surgery. However, no previous study has investigated the optimal preoperative INR target specifically in shoulder arthroplasty. The purpose of this study was to evaluate the association of preoperative INR with rates of transfusion, complication, and readmission/revision surgery in shoulder arthroplasty. Methods: Patients who underwent elective shoulder arthroplasty were identified in a national database. The primary outcome of interest was the risk for all-cause complication at 30 days postoperatively. Major and minor complication, revision surgery, and readmission rates were also investigated. Results: From 2006 to 2016, 1,014 procedures were identified who had undergone elective shoulder arthroplasty with a perioperative INR lab result within 24 hours of surgery. In our cohort, 550 patients (54.2%) were women, with an average age of 71.0 +/- 9.8 years. After controlling for confounders, patients with a preoperative INR > 1.5 were 18.9 times as likely to have a major complication as those with a preoperative INR <= 1.0 (P = 0.003). Patients with an INR of 1.25 < INR <= 1.5 did not have a statistically significant risk of minor or major complication in comparison with those with an INR <= 1.0 (P = 0.23, P = 0.67). Discussion: Although recent hip and knee arthroplasty literature has found that an INR < 1.25 may be an optimal preoperative INR goal, our results did not find an increased risk for bleeding and complication with an INR <= 1.5 for shoulder arthroplasty. These results support current guidelines recommending a preoperative INR <= 1.5 for shoulder arthroplasty.