Abstract
BACKGROUND: Adjacent segment disease (ASD) is a degenerative condition at the segment adjacent to a previously fused segment. Potential risk factors for ASD, such as posterior ligamentous complex (PLC) integrity between the upper instrumented vertebra (UIV) and the first unfused segment (UIV+1), have not been addressed. The objective of this study is to assess the PLC integrity between the UIV and UIV+1 following posterior lumbar decompression and fusion (PLDF). METHODS: A retrospective review of 122 patients who received a PLDF was performed. Patients were divided into groups based on the integrity of the PLC between the UIV and the UIV+1: PLC disrupted and PLC intact. The development of ASD was assessed using standard radiographic parameters, and reoperation rates were reviewed. RESULTS: Radiographic indicators for ASD were more common in patients of the PLC-deficient group-D and showed significantly higher mobility at the UIV+1 (p < 0.05). The overall surgical revision rate due to ASD was 7.4%, with group D (28 patients) exceeding the revision rate of group I (94 patients) by 4.3% (10.7% vs. 6.4%) over a mean follow-up of three years. The mean return to the operative report time at the UIV+1 was 2.4 years (± 1.7 years) after index surgery. CONCLUSION: We demonstrated a significant increase in mobility at the UIV+1 in lumbar fusion in patients with disrupted PLC. PLC deficiency at UIV+1 appears to contribute to the development of ASD through instability and is implicated in higher surgical revision rates.