MRI and Ultrasound of the Thoracolumbar Fascia in the Settings of Degenerative Spinal Diseases

Background and Objectives: The thoracolumbar fascia (TLF) has been implicated in low back pain, but imaging-based characterization in specific degenerative lumbar pathologies—particularly in surgical cohorts—remains limited. To evaluate TLF thickness on Magnetic resonance imaging (MRI) and Ultrasound (US) across common lumbar pathologies, examine associations with age, body mass index, disability, and assess MRI–US agreement for TLF thickness. Materials and Methods: In this prospective single-centre cohort, adults scheduled for elective lumbar surgery underwent preoperative US (short- and long-axis at L3) and review of routine lumbar MRI (axial and sagittal T1-weighted measurements at L3) using standardized protocols. Disability was assessed using the Oswestry Disability Index (ODI). Group comparisons, correlation analyses, and intraclass correlation coefficients were used to evaluate between-diagnosis differences, patient-factor associations, and MRI–US agreement. Results: Thirty-seven patients were eligible (15 lumbar spinal stenosis, 5 discs herniations, 4 spondylolisthesis, 2 scoliosis, 9 revision surgeries, 2 trauma comparators). Median TLF thickness was 0.86 mm (0.16–1.40) on axial MRI, 1.12 mm (0.47–2.33) on sagittal MRI, 2.38 mm (1.01–5.91) on US short-axis, and 2.87 mm (1.12–5.74) on US long-axis. Axial MRI thickness differed across groups (p=0.010), driven by thinner measurements in trauma versus disc herniation (p=0.031); no significant group effects were observed on sagittal MRI or US. Age correlated positively with axial MRI thickness (p=0.021). No significant correlations were detected between ODI and TLF thickness on MRI or US. MRI–US agreement was poor, indicating the modalities are not interchangeable for TLF thickness measurement. Conclusions: TLF thickness measured on MRI and US did not consistently differentiate diagnostic groups and was not associated with disability. Thickness estimates differed substantially by modality, with poor MRI–US agreement. Larger studies with standardized acquisition and reliability testing are needed to clarify the clinical and mechanistic relevance of TLF imaging in degenerative lumbar disease and to determine whether it can support phenotype-based stratification within degenerative spine disease.