Developing a toolkit for comparing safety in spine surgery.

Safety information in spine surgery is important for informed patient choice and performance-based payment incentives, but measurement methods for surgical safety assessment are not standardized. Published reports of complication rates for common spinal procedures show wide variation. Factors influencing variation may include differences in safety ascertainment methods and procedure types. In a prospective cohort study, adverse events were observed in all patients undergoing spine surgery at two hospitals during a 2-year period. Multiple processes for adverse occurrence surveillance were implemented, and the associations between surveillance methods, surgery invasiveness, and observed frequencies of adverse events were examined. The study enrolled 1,723 patients. Adverse events were noted in 48.3% of the patients. Reviewers classified 25% as minor events and 23% as major events. Of the major events, the daily rounding team reported 38.4% of the events using a voluntary reporting system, surgeons reported 13.4%, and 9.1% were identified during clinical conferences. A review of medical records identified 86.7% of the major adverse events. The adverse events occurred during the inpatient hospitalization for 78.1% of the events, within 30 days for an additional 12.5%, and within the first year for the remaining 9.4%. A unit increase in the invasiveness index was associated with an 8.2% increased risk of a major adverse event. A Current Procedural Terminology-based algorithm for quantifying invasiveness correlated well with medical records-based assessment. Increased procedure invasiveness is associated with an increased risk of adverse events. The observed frequency of adverse events is influenced by the ascertainment modality. Voluntary reports by surgeons and other team members missed more than 50% of the events identified through a medical records review. Increased surgery invasiveness, measured from medical records or billing codes, is quantitatively associated with an increased risk of adverse events.