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

Background and Objectives: The thoracolumbar fascia (TLF) has been implicated in low back pain, but imaging-based characterization in degenerative lumbar disorders, particularly in surgical cohorts, remains limited. To describe MRI-derived and US-derived TLF thickness estimates in a heterogeneous degenerative lumbar surgical cohort and explore preliminary imaging patterns and associations with selected clinical variables. Materials and Methods: In this prospective single-center 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. Twenty-six patients were included (15 with lumbar spinal stenosis, five with lumbar disc herniation, four with spondylolisthesis, and two with scoliosis). Disability was assessed using the Oswestry Disability Index (ODI). Exploratory subgroup comparisons, correlation analyses, and Bland–Altman agreement analysis were used to examine subgroup patterns, patient–factor associations, and MRI–US agreement. Results: Interpretable data were available for 19 axial MRI, 18 sagittal MRI, 19 short-axis US, 15 long-axis US, and 19 ODI assessments; paired MRI–US measurements were available in 11 cases for sagittal/long-axis analysis and 12 for axial/short-axis analysis. Mean TLF thickness was 0.89 ± 0.33 mm on axial MRI, 1.16 ± 0.48 mm on sagittal MRI, 2.53 ± 1.44 mm on short-axis US, and 2.49 ± 1.14 mm on long-axis US. Exploratory subgroup analyses showed a between-diagnosis difference only for axial-MRI-derived TLF thickness (p = 0.007), with lower thickness in disc herniation than in stenosis (p = 0.008), while sagittal MRI and US thickness measures did not differ between groups (p ≥ 0.301). ODI was not consistently associated with TLF thickness on MRI or US. Conclusions: In this exploratory surgical cohort, US-derived TLF thickness values were higher than those previously reported in the literature, suggesting possible fascial alteration in degenerative lumbar disease. However, TLF thickness was not consistently associated with disability, and MRI- and US-derived measurements should be interpreted as modality-specific estimates rather than interchangeable values. Given the small heterogeneous cohort and measurement constraints, these findings are descriptive and preliminary, but they provide an imaging framework to guide future standardized studies.