Evaluation of Adjacent Segment With Pre-Existing Degeneration Using the Cerebrospinal Fluid Occlusion Sign on MRI Before Posterior Lumbar Fusion: A Multi-Center Observational Cohort Study.

STUDY DESIGN Prospective cohort study. OBJECTIVE To evaluate whether pre-existing adjacent spinal canal stenosis (SCS) is associated with short-term outcomes after lumbar fusion surgery. METHODS We included patients with lumbar spinal stenosis treated surgically between July 2015 and December 2017 at 4 centers. All patients had the same pathology, with L4-S1 as the culprit sections. Patients were divided into 2 groups based on the cerebrospinal fluid occlusion sign on MRI at the adjacent L3/4 level. Patients without SCS (grade 0) and with mild SCS (grade 1) were classified into the non-stenosis (NS) and mild stenosis (MS) groups, respectively. All patients underwent PLIF and completed at least 1-year follow-up. The incidence of adjacent segment degeneration (ASDeg) and clinical outcomes were compared between the 2 groups. RESULTS A total of 308 patients (NS, 156; MS, 152) met the inclusion criteria. The incidence of ASDeg in the NS group (n = 40, 25.6%) was significantly lower than that in the MS group (n = 74, 48.7%; P < .001). The most frequent type of ASDeg in the 2 groups was the SCS-aggravated type. No significant difference was observed in adjacent segment disease incidence between the 2 groups (P = .243). The NS group had better outcomes according to the clinical function scores (P < .05). CONCLUSIONS The cerebrospinal fluid occlusion sign on MRI is valuable for evaluating the adjacent segment with pre-existing degeneration. Patients with mild SCS in adjacent segments were more likely to have ASDeg, and the most frequent type of ASDeg was the SCS-aggravated type at early follow-up.