Study design:

Retrospective comparative study OBJECTIVE: To identify the risk factors for the aggravation of sagittal alignment after single-level L5-S1 PLIF.

Methods:

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.

Results:

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.

Conclusions:

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.