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

Purpose: To identify risk factors for occurrence of symptomatic adjacent segment disease (ASD) after posterior lumbar instrumentation surgery. Methods: 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. Results: 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. Conclusions: 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.