# Predictive factors for segmental lordosis angle restoration in oblique lumbar interbody fusion at L4/5

## TL;DR

This study identifies factors that influence the restoration of spinal angle after a specific type of back surgery, showing that pre-surgery angle and cage placement are important.

## Contribution

The study identifies predictive factors for segmental lordosis angle restoration after OLIF surgery at L4/5.

## Key findings

- Preoperative segmental lordosis angle (SLA) strongly predicts the final SLA after surgery.
- Anterior cage placement increases SLA more than posterior placement.
- Cage subsidence reduces the final SLA by approximately 3°.

## Abstract

Retrospective study.

To identify the factors that determine segmental lordosis angle (SLA) at L4/5 after oblique lumber interbody fusion (OLIF).

A total of 65 patients who underwent single-level L4/5 OLIF (6°-lordotic cage) with posterior pedicle screw fixation without posterior osteotomy for lumbar degenerative disease were analyzed. The SLA was measured preoperatively (pre), postoperatively (post), and at the last follow-up (last) (at least 12 months) on the midline sagittal CT views. Demographics, surgical, and radiological factors were included. Clinical outcomes (ODI and VAS) were assessed.

The mean preoperative SLA at L4/5 increased from 7.1 ± 3.9° preoperatively to 9.8 ± 3.4° postoperatively (P < 0.001) and was maintained as 9.1 ± 3.5° at the last follow-up (P < 0.001). Multiple regression analysis revealed that Pre-SLA, cage position and cage subsidence were predictors of Last-SLA. Small-angle group (Pre-SLA < 6°) showed a stronger capacity in the increase of SLA (Pre-SLA – Post-SLA) and change of SLA (Last-SLA – Pre-SLA) than large-angle group (Pre-SLA ≥ 6°). Anterior cage position is associated with the more increase of SLA than posterior cage position. Cage subsidence led to approximately 3° in decrease of SLA (Last-SLA – Post-SLA). No significant correlation was observed between Last-SLA and clinical outcomes.

The Last-SLA is strongly associated with the Pre-SLA condition and OLIF has a higher capability to restore SLA in patients with a smaller preoperative SLA. To achieve a greater SLA, surgeons should try to insert cage in the anterior disc space and reduce the occurrence of cage subsidence.