Comparison of 90-day complications and two-year reoperation rates between anterior and posterior interbody fusion for single-level degenerative spondylolisthesis.

Background: For the surgical treatment of single-level degenerative spondylolisthesis (DS), patients can be treated with either an anterior or posterior interbody fusion. Prior studies have shown that patients with symptomatic degenerative spondylolisthesis treated surgically maintain substantially greater pain relief and improvement in function when compared to those treated non-operatively, but no consensus has emerged between which approach results in the best outcomes. Methods: The PearlDiver MARINER database was queried for patients with single-level DS who underwent either an anterior or posterior lumbar interbody fusion. Both populations were compared on multiple outcomes, including reoperation, post-operative complications, and readmission rates at 90 days, as well as rates of reoperation and cauda equina syndrome two-years postoperatively. Results: At 90 days patients who underwent anterior interbody were found to have higher rates of DVT (OR 2.53, 95% CI 1.74 - 3.70, p<0.001), ileus (OR 1.43, 95% CI 1.25 - 1.64, p<0.001), and readmission (OR 1.28, 95% CI 1.19 - 1.38, p<0.001). Patients who underwent posterior interbody fusion were found to have higher rates of revision procedures (OR 0.63, 95% CI 0.59 - 0.66, p<0.001), transfusion (OR 0.68, 95% CI 0.58 - 0.78, p<0.001), acute kidney injury (OR 0.84, 95% CI 0.75 - 0.95, p=0.0046), and cauda equina syndrome (OR 0.53, 95% CI 0.40 - 0.69, p<0.001). At 2 years, patients who underwent posterior fusion required revision procedures (OR 0.70, 95% CI 0.67 - 0.74, p<0.001) and developed cauda equina syndrome (OR 0.62, 95% CI 0.50 - 0.77, p<0.001) at a higher rate than those who underwent anterior fusion. Conclusions: Patients who underwent anterior interbody fusion for treatment of degenerative spondylolisthesis were found to have increased rates of DVT, ileus, and were more likely to be readmitted to the hospital within 90 days, while patients who underwent posterior interbody fusion were found to have higher rates of reoperation, transfusion, AKI, and cauda equina syndrome. Increased rates of reoperation and development of cauda equina in the posterior fusion group persisted at 2 years post-operatively.