Study design: Retrospective follow-up study of patients undergoing multiple (two or more) reoperations after initial lumbar discectomy using an administrative database. OBJECTIVES: To identify the population-based risk of multiple reoperations after lumbar discectomy and to analyze factors associated with the risk.

Summary of background data: Although multiple reoperations after initial lumbar discectomy are likely uncommon, research to better understand reasons for and outcomes of reoperations is needed because of the large number of discectomies performed.

Methods: Data on all lumbar spine operations during 1987-1998 were obtained from the Finnish Hospital Discharge Register. The patient's initial disc operation during the study period was linked to subsequent operations, and patients with two or more reoperations were analyzed further. The risk of multiple reoperations was determined using the methods of event history analysis. RESULTS: Among 35,309 patients undergoing an initial discectomy, 4943 (14.0%) had at least one reoperation and 803 (2.3%) had two or more reoperations. A total of 63% of the second reoperations were discectomies, 14% were fusions, and the remaining 23% were decompressions. Patients with one reoperation after lumbar discectomy had a 25.1% cumulative risk of further spinal surgery in a 10-year follow-up. Reduced risk was seen when the first reoperation took place more than 1 year after the initial discectomy (relative risk 0.83, 95% confidence interval 0.72-0.96), in patients for whom the first reoperation had been a fusion (relative risk 0.27, 95% confidence interval 0.12-0.61), and in patients 50-64 years of age (relative risk 0.62, 95% confidence interval 0.48-0.79).

Conclusion: Patients with one reoperation after lumbar discectomy are at considerable risk of further spinal surgery.