Incidence of adjacent segment disease requiring reoperation after lumbar laminectomy without fusion: A study of 398 patients

BACKGROUND: Adjacent segment disease (ASD) has not been described after lam-inectomy without fusion. OBJECTIVE: To determine the incidence of ASD after a 1- or 2-level lumbar laminectomy. METHODS: We retrospectively reviewed medical records of all patients who underwent 1- or 2-level, bilateral lumbar laminectomy without fusion for degenerative spinal disease (all follow-up ≥1 year). ASD was defined as clinical and/or radiographic evidence of degenerative spinal disease that required reoperation at the level above or below the index laminectomy. RESULTS: Of the 398 patients, the incidence of ASD requiring reoperation was 10%. The 39 ASD cases were almost equally distributed at L2-L3 (31%), L3-L4 (26%), and L5-S1 (31%), and to a lesser extent at L4-L5 (15%) (P = .51). The ASD incidences of 10% and 9% were equivalent after a 1- and 2-level laminectomy, respectively (P = .76). Rostral ASD was statistically more common than caudal ASD after both the 1- (P < .001) and 2- (P < .001) level laminectomy. Of the 39 ASD cases, 95% required laminectomy, 26% dis-cectomy, and 49% fusion. Average time to ASD was 4 years. After a Kaplan-Meier analysis, time to reoperation for ASD was equivalent among the 1- and 2-level lam-inectomy cohorts (log-rank test, P = .13). CONCLUSION: The cumulative incidence of ASD requiring reoperation was 10% over a mean of 4 years. Both the 1- and 2-level laminectomy cohorts experienced equivalent incidences and rates of ASD. Of the 39 operations for ASD, about half required a fusion.