Thromboembolic Events After Arthroscopic Knee Surgery: Increased Risk at High Elevation

Purpose To evaluate the incidence of thromboembolic events in patients undergoing arthroscopic surgery of the knee in centers located at elevations near sea level and compare those rates with the patients undergoing the same operations in centers at high elevation. Methods A retrospective review was conducted using a database of a major health care system with surgery centers located throughout the United States. More than 115 centers located in 15 different states were analyzed for any reported thromboembolic events including deep vein thromboses and pulmonary embolism (PE) in patients who had undergone knee arthroscopy over a 2-year period. The centers located at elevations lower than 1,000 ft were considered sea level centers. Centers located at elevations above 4,000 ft were considered high-elevation centers. Centers located between 1,000 ft and 4,000 ft elevation were excluded. Results A total of 35,877 patients underwent a knee arthroscopy at a low-elevation center and 10,181 patients underwent a knee arthroscopy at a high-elevation center between 2011 and 2012. During that same time period, 45 total venous thromboembolic events (VTEs) including 12 PEs occurred at centers considered low elevation, whereas 50 VTEs including 4 PEs occurred at centers considered high elevation. The incidence of VTE at low-elevation centers was 0.13%. The incidence of VTE at high-elevation centers was 0.49%. The difference was statistically significant, P < .0001. The relative risk of developing a VTE was 3.8 times higher at high elevation. There was no difference in PE incidence between high- and low-elevation centers (0.04% vs 0.03%, respectively; P = .78). Conclusions Patients undergoing arthroscopic procedures of the knee in centers at high elevation are at 3.8 times higher risk of developing a VTE than those undergoing the same procedures in centers at low elevations. There was no observed increased risk of PE. Level of Evidence Level III, retrospective comparative study. To evaluate the incidence of thromboembolic events in patients undergoing arthroscopic surgery of the knee in centers located at elevations near sea level and compare those rates with the patients undergoing the same operations in centers at high elevation. A retrospective review was conducted using a database of a major health care system with surgery centers located throughout the United States. More than 115 centers located in 15 different states were analyzed for any reported thromboembolic events including deep vein thromboses and pulmonary embolism (PE) in patients who had undergone knee arthroscopy over a 2-year period. The centers located at elevations lower than 1,000 ft were considered sea level centers. Centers located at elevations above 4,000 ft were considered high-elevation centers. Centers located between 1,000 ft and 4,000 ft elevation were excluded. A total of 35,877 patients underwent a knee arthroscopy at a low-elevation center and 10,181 patients underwent a knee arthroscopy at a high-elevation center between 2011 and 2012. During that same time period, 45 total venous thromboembolic events (VTEs) including 12 PEs occurred at centers considered low elevation, whereas 50 VTEs including 4 PEs occurred at centers considered high elevation. The incidence of VTE at low-elevation centers was 0.13%. The incidence of VTE at high-elevation centers was 0.49%. The difference was statistically significant, P < .0001. The relative risk of developing a VTE was 3.8 times higher at high elevation. There was no difference in PE incidence between high- and low-elevation centers (0.04% vs 0.03%, respectively; P = .78). Patients undergoing arthroscopic procedures of the knee in centers at high elevation are at 3.8 times higher risk of developing a VTE than those undergoing the same procedures in centers at low elevations. There was no observed increased risk of PE.