Prediction of Postoperative Segmental Lordosis at L5 to S1 After Single-Level Anterior Lumbar Interbody Fusion

Anterior lumbar interbody fusion (ALIF) is used to improve spinopelvic alignment, most commonly by increasing segmental lordosis (SL) at L5 to S1. Achieving certain radiographic parameters is critical for good patient outcomes. However, the relationships between pre- and postoperative SL and interbody dimensions are inexact and have not been well studied. This study investigated the relationships between postoperative SL at L5 to S1, ALIF cage angle, and preoperative radiographic measurements to improve the predictability of surgical radiographic outcomes after L5 to S1 ALIF.

A single-center database was retrospectively reviewed for patients who underwent L5 to S1 ALIF from January 2017 to December 2022. Patients with posterior percutaneous instrumentation were included in the study, but patients with posterior decompression or facetectomies at L5 to S1 were excluded. Pre- and postoperative scoliosis films and patient surgical data were analyzed. A multilinear regression analysis was performed to create a predictive model of postoperative L5 to S1 SL.

This study evaluated 46 single-level L5 to S1 ALIFs. Using mixed-effects linear regression analysis, postoperative L5 to S1 SL can be predicted with statistical significance (P < 0.001) and power of 0.98 if the cage angle and preoperative L5 to S1 SL are known using the following formula: SL_post = 8.741 + (0.454 × C) + (0.595 × SL_pre), where SL_post is postoperative L5 to S1 SL in degrees, C is cage angle in degrees, and SL_pre is preoperative L5 to S1 SL in degrees.

Cage angle and preoperative L5 to S1 SL were predictive of postoperative SL after L5 to S1 ALIF. The ability to predict postoperative radiographic values is critically important for good patient outcomes, and efforts should be made to develop more sophisticated mathematical models.