Impact of Patient-specific Factors and Spinopelvic Alignment on the Development of Adjacent Segment Degeneration After Short-segment Lumbar Fusion

Prospective cross-sectional cohort study. OBJECTIVES: The main purpose of this study was to evaluate the association between demographical, surgery-related and morphologic parameters, and the development or progress of adjacent segment degeneration (ASD) after short-segment lumbar fusions. SUMMARY OF BACKGROUND DATA: ASD is a major long-term complication after lumbar fusions. Possible risk factors are related to the patients’ demographics, spinopelvic anatomy, or preoperative lumbar intervertebral disk conditions, but the role of these parameters is still not clear. METHODS: A prospective cross-sectional study of 100 patients who underwent 1- or 2-level open lumbar transforaminal interbody fusions due to a lumbar degenerative pathology was conducted. Demographical, radiologic findings, and magnetic resonance imaging features were analyzed to identify factors associated with ASD in 5-year follow-up. RESULTS: ASD patients showed higher level of pain (P=0.004) and disability (P=0.020) at follow-up. In univariate analysis, older age (P=0.007), upper-level lumbar fusion (P=0.007), lower L4-S1 lordosis (P=0.039), pelvic incidence-lumbar lordosis mismatch (P=0.021), Pfirrmann grade III or higher disk degeneration (P=0.002), and the presence of disk bulge/protrusion (P=0.007) were associated with ASD. In multivariate analysis, the presence of major degenerative sign (disk degeneration and/or disk bulge) was the significant predictor for developing ASD (odds ratio: 3.85, P=0.006). CONCLUSION: By examining the role of different patient- and procedure-specific factors, we found that preoperative major degenerative signs at the adjacent segment increase the risk of ASD causing significantly worse outcome after short-segment lumbar fusion. On the basis of our results, adjacent disk conditions should be considered carefully during surgical planning.