Posterior lumbar interbody fusion for degenerative spondylolisthesis; slippage reduction can be a risk factor for adjacent segment disease.

Several risk factors for adjacent segment disease (ASD) after posterior lumbar interbody fusion (PLIF) have been reported. However, the reducing the slipped vertebra has not been investigated as a risk factor for ASD. The objective of this study is to identify the risk factors for ASD following single-segment PLIF in patients with L4 spondylolisthesis, with a particular focus on the reduction of vertebral body slippage. Fifty-two patients who underwent PLIF at the L4-L5 level for L4 degenerative spondylolisthesis were investigated. Patients were divided into two groups: the ASD group and the non-ASD group. The ASD group consisted of 12 of the 52 patients (23.1%). %Slip before surgery and at follow-up, Δ%Slip (Δ%Slip = %Slip before surgery - %Slip at follow-up), L4-L5 interbody height, and L4-L5 lordosis angle were evaluated. Stepwise multivariate regression analysis revealed Δ%Slip to be a risk factor for ASD (odds ratio: 1.22, 95% confidence interval: 1.04–1.43, p = 0.015). In the receiver operating characteristic analysis, the cutoff value for Δ%Slip was 7.3% (sensitivity: 75.0%, specificity: 67.5%, area under the curve = 0.725). Our findings suggest that the reduction of L4 slippage may contribute to the development of ASD in patients with L4 spondylolisthesis.