Adjacent segment disease after posterior lumbar instrumentation surgery for degenerative disease: Incidence and risk factors

To identify risk factors for occurrence of symptomatic adjacent segment disease (ASD) after posterior lumbar instrumentation surgery. This retrospective study evaluated 630 patients who underwent posterior lumbar transpedicular instrumentation for degenerative lumbar disorders between April 2008 and April 2012. On the basis of developing ASD at follow-up, patients were categorized into two groups: the ASD group and the non-ASD (N-ASD) group. These two groups were compared for patient characteristics, surgical variables, and radiographic parameters to investigate the possible predictive factors of ASD. Of the 630 individuals participated in the study, 76 (12.1%) patients had ASD. Mean and standard deviation of age were 61.37 ± 4.12 years for the ASD group and 62.37 ± 3.9 for the N-ASD group (p = 0.79). The average follow-up period was 51 ± 2.2 months in the ASD group and 52 ± 2.3 months in the N-ASD group (p = 0.691). There were no significant differences between the two groups in terms of gender, diabetes mellitus (DM), hypertension, smoking, and osteoporosis, with all p > 0.05. The logistic regression analysis demonstrated that higher preoperative body mass index (BMI; odds ratio (OR) 1.233, p = 0.005), preoperative disc degeneration (OR 1.033, p = 0.024), decreased postoperative lumbar lordosis (OR 3.080, p = 0.011), fusion at more than four levels (OR 4.280, p = 0.014), and intraoperative superior facet joint violation (OR 7.480, p = 0.009) were independently associated with ASD. Patients with higher preoperative BMI, preoperative disc degeneration, decreased postoperative lumbar lordosis, fusion at more than four levels, and intraoperative superior facet joint violation have a statistically significant increased risk of developing ASD