A total of 1441 patients in the HEALTH trial who received total hip arthroplasty or hemiarthroplasty for a femoral neck fracture were included in this sub-analysis assessing the incidence of serious adverse events and factors associated with serious adverse events. Of the 1441 patients analyzed, 370 patients experienced a serious adverse event. The most common serious adverse events were cardiac (n=105), respiratory (n=77) and neurological (n=52) events. 35.4% of serious adverse events occurred within the first 30 days post-operation. A BMI greater than 30, compared to a BMI between 18.5 and 29.9, was found to result in a lower risk of serious adverse events (p=0.04). Total hip arthroplasty was associated with a significantly higher risk of serious adverse events vs bipolar hemiarthroplasty (p=0.03). In addition, not using pre-operative traction was associated with a significantly higher risk of serious adverse events compared to pre-operative traction usage (p<0.01). Age, use of femoral cementing, and use of canal pressurization were not associated with an increased risk of serious adverse events.