Bone remodeling, not inflammation, as the predominant pathology in modic type 1 lesions of the lumbar spine

Lesions of the vertebral endplates (Modic changes) are associated with low back pain (LBP), and different pathological processes, including inflammation, have been proposed as causative. This study aimed to explore the relationship between [18F]FDG uptake (inflammation) and [18F]NaF uptake (bone remodeling) and patient-reported back pain as well as conventional MRI detected endplate changes.

Participants were selected from an IRB-approved study, creating 2 arms: [18F]NaF (n = 11) and [18F]FDG (n = 11). Scans were performed on a 3.0 T PET-MRI scanner. An MSK radiologist rated endplates changes using Modic classification and a relative scale: None; only edema; edema > fat; edema=fat; edema< fat; only fat. Radiotracer uptake (SUVmax) in endplate-adjacent bone was measured using ROIs. VAS scores (0-10) for back pain were recorded before imaging. Generalized estimating equations assessed associations between pain and radiotracer uptake as outcomes and radiologic findings as predictors, adjusted for age, sex, and body mass index (BMI).

The study included 220 endplates from 22 patients (110 per arm). Overall, pain was positively associated with edematous lesions (beta 0.21, P = .024) but not with fatty changes (beta 0.10, P = .567). In the [18F]NaF arm, tracer uptake was associated with edematous lesions (beta 1.79, P = .001) and with pain (beta 0.18, P = .007). In the [18F]FDG arm, tracer uptake was negatively associated with edematous lesions (beta -0.11, P = .013) and showed no significant association with pain (beta -1.50, P = .064).

Our study shows that [18F]NaF-PET-MRI detected bone-remodeling is more closely linked to painful vertebral end-plate degeneration than inflammatory [18F]FDG signal.