Validation of adverse events after hip arthroplasty: a Swedish multi-centre cohort study.

Objectives Preventing adverse events (AEs) after orthopaedic surgery is a field with great room for improvement. A Swedish instrument for measuring AEs after hip arthroplasty based on administrative data from the national patient register is used by both the Swedish Hip Arthroplasty Register and the Swedish Association of Local Authorities and Regions. It has never been validated and its accuracy is unknown. The aim of this study was to validate the instrument's ability to detect AEs, and to calculate the incidence of AEs following primary hip arthroplasties. Design Retrospective cohort study using retrospective record review with Global Trigger Tool methodology in combination with register data. Setting 24 different hospitals in four major regions of Sweden. Participants 2000 patients with either total or hemi-hip arthroplasty were recruited from the SHAR. We included both acute and elective patients. Primary and secondary outcome measures The sensitivity and specificity of the instrument. Adjusted cumulative incidence and incidence rate. Results The sensitivity for all identified AEs was 5.7% (95% CI: 4.9% to 6.7%) for 30 days and 14.8% (95% CI: 8.2 to 24.3) for 90 days, and the specificity was 95.2% (95% CI: 93.5% to 96.6%) for 30 days and 92.1% (95% CI: 89.9% to 93.8%) for 90 days. The adjusted cumulative incidence for all AEs was 28.4% (95% CI: 25.0% to 32.3%) for 30 days and 29.5% (95% CI: 26.0% to 33.8%) for 90 days. The incidence rate was 0.43 AEs per person-month (95% CI: 0.39 to 0.47). Conclusions The AE incidence was high, and most AEs occurred within the first 30 days. The instrument sensitivity for AEs was very low for both 30 and 90 days, but the specificity was high for both 30 and 90 days. The studied instrument is insufficient for valid measurements of AEs after hip arthroplasty.