Development and internal validation of a clinico-radiological classification system for lumbar adjacent segment degeneration after TLIF.

BACKGROUND

Adjacent segment degeneration (ASD) following transforaminal lumbar interbody fusion (TLIF) lacks a standardized classification system that integrates both clinical and radiological parameters. We aimed to develop and internally validate a novel clinico-radiological classification system for lumbar ASD after TLIF and to evaluate its association with surgical intervention.

METHODS

We retrospectively analyzed 150 patients who underwent one- or two-level TLIF with a minimum follow-up of 5-years. Clinical variables (low back pain [LBP], radiculopathy, neurogenic claudication, and neurological deficit) and radiographic/magnetic resonance imaging (MRI) findings were assessed. Latent class analysis (LCA) identified 5 distinct classes, forming a five-grade system: Grade 0: Nil or occasional LBP with normal imaging; Grade 1: Continuous LBP with mild radiological degeneration without instability; Grade 2: Radicular pain with moderate degeneration and/or instability; Grade 3: Neurogenic claudication with advanced degeneration and severe central stenosis; and Grade 4: Neurological deficit and/or proximal junctional kyphosis or failure. Internal validation was performed in 30 independent cases using Fleiss' kappa. Firth's penalized logistic regression was used to identify predictors of surgical intervention.

RESULTS

The classification demonstrated substantial inter-observer agreement (κ = 0.74) and excellent intra-observer reliability (κ = 0.82). Surgical intervention was strongly associated with higher grades: 87% of patients in Grades 3-4 underwent surgery compared to 6.7% in Grades 0-2 (p < .001). High-grade ASD (odds ratio [OR] 24.30; p < .001) and diabetes mellitus (OR = 3.24; p = .005) were independent predictors of surgery. The average grading time was 2-3 minutes per case.

CONCLUSIONS

This novel clinico-radiological classification system for lumbar ASD after TLIF is reliable, practical, and strongly associated with surgical decision-making. It may aid in clinical stratification and follow-up planning. Prospective multicenter validation is warranted.