The iLLIF score: a predictive success scoring system for indirect decompression in lateral lumbar interbody fusion

Lateral lumbar interbody fusion (LLIF) is a minimally invasive technique for degenerative lumbar disease, but selecting appropriate candidates for indirect decompression remains challenging. This study developed and internally validated the iLLIF score to estimate the likelihood of successful indirect decompression without additional intervention.

A retrospective cohort study was conducted on 200 patients who underwent LLIF between 2014 and 2024. Patients were categorized based on clinical outcomes: successful (no intervention or reoperation at the index level within 12 months) versus unsuccessful. Independent preoperative predictors of success were identified using multivariate logistic regression. A five-point scoring system (iLLIF Score) was derived from significant predictors and validated using the area under the receiver operating characteristic curve (AUC).

Among the 200 patients, 168 (84%) achieved successful outcomes. Multivariate analysis identified five independent preoperative predictors of success: (1) rest symptoms less than 50%, (2) reducible disc height greater than 13%, (3) radiographic instability, (4) absence of severe lateral recess stenosis, and (5) no history of previous surgery at an adjacent level. Each factor was assigned one point, yielding a score ranging from 0 to 5. A cutoff of ≥ 3 provided the best balance between sensitivity and specificity. The scoring model demonstrated high predictive performance (AUC 0.973; 95% CI 0.946-1.000).

The iLLIF Score is a simple, internally validated preoperative tool that may help estimate the likelihood of successful indirect decompression following LLIF. It may assist in patient selection and surgical planning, although external validation is required before routine clinical implementation.