Analysis of risk factors affecting lumbosacral pseudoarthrosis in multi-segmental fusion: a CT-based study

This study aimed to evaluate factors influencing the occurrence of pseudoarthrosis in L5-S1 fusion during long-level fusion.

A retrospective analysis was conducted on 88 patients who underwent L5-S1 interbody fusion with minimum 2 years of follow up. The fusion status of the lumbosacral joint was evaluated using computed tomography of postoperative two year and patients were divided into union and nonunion group. The study assessed sagittal parameters, clinical outcomes, and radiological findings. Univariate and multivariate analyses were employed to identify predictors of pseudoarthrosis in lumbosacral joint.

Among 88 patients, 70 achieved union, while 18 (20.5%) had pseudoarthrosis. Multivariate analysis identified male gender and prior fusion in other segments as nonunion predictors (p = 0.034, OR = 3.665; p = 0.045, OR = 3.099, respectively). S1 screw loosening was significantly higher in the nonunion group (p = 0.002).

Interbody fusion at the lumbosacral joint demonstrates a relatively high rate of nonunion, especially in males and patients with prior fusion in other segments. Caution is warranted in performing interbody fusion at the lumbosacral joint in such cases due to an elevated risk of nonunion. Loosening of S1 screw warrants careful consideration to prevent pseudoarthrosis.