Adjacent Segment Disease After Single Segment Posterior Lumbar Interbody Fusion for Degenerative Spondylolisthesis

Study Design. A retrospective study. Objective. The aim of this study was to investigate the incidence of adjacent segment disease (ASD) at 2, 5, and 10 years after primary posterior lumbar interbody fusion (PLIF), and clinical features of ASD. Summary of Background Data. Few reports have examined ASD after PLIF with more than 10 years of follow-up. Furthermore, no reports have examined limited conditions of preoperative pathology, fusion segment, and fusion method with long follow-up. Methods. Data were reviewed for 128 patients who underwent single-segment PLIF for L4 degenerative spondylolisthesis and could be followed for at least 10 years. Mean age at the time of surgery was 63 years, and mean follow-up was 12.4 years. Follow-up rate was 62.4%. ASD was defined as radiological ASD (R-ASD), radiological degeneration adjacent to the fusion segment by plain X-rays and magnetic resonance imaging (MRI); symptomatic ASD (S-ASD), a symptomatic condition due to neurological deterioration at the adjacent segment degeneration; and operative ASD (O-ASD), S-ASD requiring revision surgery. Results. Incidences of each ASD at 2, 5, and 10 years after primary PLIF were 19%, 49%, and 75% for R-ASD, 6%, 14%, and 31% for S-ASD, and 5%, 9%, and 15% for O-ASD, respectively. O-ASD incidence was 24% at final follow-up. O-ASD peak was bimodal, at 2 and 10 years after primary PLIF. O-ASD was mainly observed at the cranial segment (77%), followed by the caudal segment (13%) and both cranial and caudal segments (10%). With respect to O-ASD pathology, degenerative spondylolisthesis was observed in 52%, spinal stenosis in 39%, and disc herniation in 10%. Conclusion. Incidences of R-ASD, S-ASD, and O-ASD at 10 years after primary PLIF were 75%, 31%, and 15%, respectively. With respect to O-ASD pathology, degenerative spondylolisthesis at the cranial segment was the most frequent. Level of Evidence: 4