Adjacent Segment Disease After Posterior Lumbar Interbody Fusion: A Case Series of 1000 Patients

STUDY DESIGN: Retrospective study. OBJECTIVE: There have been few reports of adjacent segment disease (ASD) after posterior lumbar interbody fusion (PLIF) with large numbers and long follow-up. The purpose of this study was to investigate (1) ASD incidence and time periods after primary PLIF, (2) repeat ASD incidence and time periods, and (3) ASD incidence and time periods by fusion length, age, and preoperative pathologies. METHODS: A total of 1000 patients (average age 67 years, average follow-up 8.3 years) who underwent PLIF for degenerative lumbar disorders were reviewed. ASD was defined as a symptomatic condition in which revision surgery was required. RESULTS: The overall ASD rate was 9.0%, and the average ASD period was 4.7 years after primary surgery. With respect to clinical features of ASD, degenerative spondylolisthesis at the cranial fusion segment was the most frequent. In terms of repeat ASD, second and third ASD incidences were 1.1% and 0.4%, respectively. As for ASD by fusion length, age, and preoperative pathologies, ASD incidence was increased by fusion length, while the time period to ASD was significantly shorter in elderly patients and those with degenerative lumbar scoliosis. CONCLUSIONS: In the present study, the overall ASD incidence was 9.0%, and the average ASD period was 4.7 years after primary operation. Second and third ASD incidences were 1.1% and 0.4%, respectively. Fusion length affected the ASD incidence, while aging factor and preoperative pathology affected the ASD time period.