Risk Factors for the Aggravation of Sagittal Balance After L5–S1 Posterior Lumbar Interbody Fusion

Abstract

Retrospective comparative study OBJECTIVE: To identify the risk factors for the aggravation of sagittal alignment after single-level L5-S1 PLIF. Eighty-six patients who underwent L5-S1 PLIF were divided into two groups according to the postoperative changes in the segmental angle (SA; group I: increase; group D: decrease). The two groups were compared in terms of demographic, clinical, and radiological outcomes. Multivariate logistic regression analysis was performed to identify the risk factors for aggravation of sagittal alignment. Of the study patients, 39 (45%) were categorized as group I and 47 (55%) as group D. The demographic and clinical parameters were not significantly different between the two groups. Group D showed postoperative deteriorations in the local sagittal parameters, including lumbar lordosis (LL; p=.034), sacral slope (p=.012), and pelvic tilt (p=.003). In contrast, group I showed improved LL after surgery (p=0.021). Large preoperative values of lumbosacral angle (LSA; odds ratio [OR], 1.287; p=.001), SA (OR, 1.448; p<.001), and flexion LSA (OR, 1.173; p=.011) were independent risk factors for the aggravation of sagittal balance. Surgeons treating patients with large preoperative SA, LSA, and flexion LSA at L5-S1 level should be cautious of the possible aggravation of sagittal balance after L5-S1 PLIF and may consider different surgical approaches such as anterior or oblique lumbar interbody fusion.