Impact of patient-specific factors and spinopelvic alignment on the development of adjacent segment degeneration after short-segment lumbar fusion

Abstract Objectives: The main purpose of the study was to analyse the different demographical, morphological, and surgery-related parameters influencing the development or progress of degeneration in adjacent segments after routine, short-segment lumbar fusions.Summary of Background data: Adjacent segment degeneration (ASD) considered as a major long-term complication after lumbar fusions. Possible risk factors are related to the patients’ demographics, spinopelvic anatomy or preoperative lumbar intervertebral disc conditions. The current literature lacks of well-designed prospective studies focusing on the multidimensional nature of the condition.Methods: A prospective cohort of 100 patients who underwent one- or two-level lumbar transforaminal interbody fusions due to lumbar degenerative pathology was conducted. Demographical, radiological findings (spinopelvic parameters, adjacent segmental radiological as well as magnetic resonance imaging (MRI) features) and long-term outcome data (5-year) were analysed to identify factors associated with ASD. Results: ASD patients showed higher level of pain (p=0.004) and disability (p=0.020) at follow-up. In univariate analysis, older age, upper-level lumbar fusion (p=0.007), lower L4-S1 lordosis (p=0.039), PI-LL mismatch (p=0.021), Pfirrmann grade III or higher disc degeneration (p=0.002) and the presence of disc bulge/herniation were (p=0.007) associated with ASD. Final result of multivariate analysis showed major degenerative sign (disc degeneration and/or disc bulge) as a risk factor (OR 3.85, CI 1.43-10.37, 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. Adjacent disc conditions should be considered carefully during surgical planning.