A higher altitude is an independent risk factor for venous thromboembolisms following total shoulder arthroplasty.

INTRODUCTION: High altitudes lead to physiological changes that may predispose to venous thromboembolisms (VTE) including deep vein thrombosis (DVT) and pulmonary embolism (PE). No prior study has evaluated if there is also a higher risk of VTEs after total shoulder arthroplasties (TSAs) performed at higher elevations compared to lower elevations. The purpose of this study was to identify if undergoing TSA at a higher altitude center (>4000 feet above sea level) is an independent risk factor for a postoperative VTE.
METHODS: A retrospective review was performed from 2005 to 2014 using the Medicare Standard Analytical Files of the Pearl Diver database (Pearl Diver Technologies, West Conshohocken, PA, USA). The inclusion criteria for the study group consisted of all patients in the database undergoing primary TSAs at an altitude above 4000 feet. Patients were queried using the International Classification of Disease 9th revision codes (ICD-9). All patients undergoing primary TSA were queried using ICD-9 procedure code 81.80. Patients were filtered using the zip codes of the hospitals where the procedure occurred and were separated into high (>4,000 ft) and low (<100 ft) altitudes. Patients undergoing TSA in altitudes <100 ft represented the control group. Patients with a history of VTE, DVT, PE, and coagulation disorders were excluded from the study. Patients in the study group were randomly matched 1:1 according to age, gender, and comorbidities. Two mutually exclusive cohorts were formed and rates of VTE, DVT, and PE were analyzed and compared. Statistical analysis was performed using the programming language R (University of Auckland, New Zealand). An alpha value less than 0.05 was considered statistically significant.
RESULTS: In the first 30 postoperative days, patients undergoing TSA at a higher altitude experienced a significantly higher rate of PEs (odds ratio [OR], 39.5; P = <0.001) when compared to similar patients at lower altitudes. This trend was also present for PE (OR, 2.02; P < 0.03) at 90 days postoperatively.
CONCLUSION: TSAs performed at higher altitudes (>4000 feet) have a higher rate of acute postoperative PEs in the first 30 days and 90 days postoperatively when compared to matched patients receiving the same surgery at a lower altitude (<100 feet). TSA patients at high altitude should be counseled on these increased risks.