Radiologic adjacent segment degeneration 2 years after lumbar fusion for degenerative spondylolisthesis

IntroductionLumbar fusion is now a currently accepted treatment for degenerative lumbar spondylolisthesis (DLSP), but may induce adjacent segment degeneration (ASD). The present study hypothesis was that there are radiological parameters associated with ASD. The study objective was to determine predictive factors of ASD.Material and methodsA single-center retrospective study included patients operated on between 2006 and 2013 for DLSP. Radiological parameters were analyzed on preoperative, immediate postoperative and final follow-up lateral X-ray. ASD was defined by the following adjacent segment criteria: > 3 mm anteroposterior translation, > 10° segmental kyphosis, or > 50% loss of disc height.ResultsOne hundred and seven patients were included: 79% female; mean age, 67 ± 10.2 years. Fusion involved 1 level in 67% of cases and 2 or more in 33%, with transforaminal lumbar interbody fusion (TLIF) in 27% of cases. There was overall significant gain in lumbar lordosis (mean, 3.1°; P = 0.04). At a mean 27.8 months’ follow-up, 29% of cases showed ASD and 10% required surgical reintervention. Preoperative anterior imbalance and long fusion (> 2 levels) were significantly associated with ASD (OR = 2.81, 95% CI [1.17–6.74] versus OR = 2.76, 95% CI [1.15–6.63]). There were no significant differences according to postoperative radiological parameters, or to TLIF (OR = 1.8, 95% CI [0.7–4.4]).ConclusionTwenty-nine percent of patients developed ASD, with a surgical revision rate of 10%. ASD risk factors comprised high number of instrumented levels and preoperative sagittal imbalance.Level of evidenceIV, retrospective cohort.