Lumbar adjacent segment degeneration after spinal fusion surgery: a systematic review and meta-analysis

Introduction: Adjacent segment degeneration is among the most recognized longterm complications of lumbar surgery for degenerative spine pathologies with a relevant impact in spine surgical and clinical practice. It is reported a incidence of clinical adjacent segment disease between 5-30% of patients undergoing spinal fusion. We aimed to evaluate the main clinical and surgical risk factors for developing adjacent segment disease. Evidence acquisition: A systematic review and meta-analysis of the pertinent literature was performed, according to PRISMA and PICO guidelines, focusing on clinical and radiological adjacent segment disease. We exclusively included studies reporting demographic and clinical data, and surgical details published from 30 September 2015 to 30 September 2020. The effect of considered risk factors on the presence of adjacent segment disease was explored with a random-effects model. Evidence synthesis: A total of 15 scientific publications, corresponding to 6253 patients, met the inclusion criteria for the qualitative and quantitative analysis. 720 of the patients developed a clinical and/or radiological adjacent syndrome disease, and 473 have been surgically managed. Ten articles qualified for the comparative geographical analysis. Advanced age and obesity are relevant risk factors for developing lumbar adjacent segment degeneration. Our data also reported a higher prevalence of adjacent segment degeneration in Western populations than in Eastern populations. The interbody fusion has a protective role toward lumbar adjacent segment degeneration. Conclusions: This study highlighted multifactorial issues regarding adjacent segment disease: clinical, anatomical, biomechanical, and radiological features. In view of increasing life expectancy and spinal surgery procedures, extensive multicenter studies will be needed to define the correct management of the adjacent segment disease.