Prone Position MRI of the Lumbar Spine in Patients With Low Back Pain and/or Radiculopathy Refractory to Treatment.

BACKGROUND: There are patients with limiting low back pain (LBP) with or without radicular pain in whom conventional supine magnetic resonance imaging (MRI) show no causative pathology. Despite the limitations of dynamic axially loaded MRI examinations, these imaging studies have shown a striking ability to diagnose pathology unrecognized by conventional MRI. The difference in findings between supine and prone MRI with patient symptom correlation has not been studied. METHODS: Nineteen patients suffering from chronic moderate-to-severe LBP and/or radicular pain nonresponsive to conventional therapy or interventional treatment, were included in this study. Both supine and prone MRIs were performed and analyzed by a neuroradiologist. Specific supine and prone measurements were registered, including spinal canal area, lateral recess diameter, foraminal area, and ligamentum flavum thickness. Three-dimensional  MRI reconstructions of varying pathology patterns were created. RESULTS: The mean patient age was 48.7 years (range [R]: 30-69), 63% of patients were women. The mean numeric pain score  was 6.5 (R: 4-8). In 52.6% of cases, disc pathology/increased disc pathology was seen only on prone imaging. We observed significant buckling and increased thickness of the ligamentum flavum in 52.6 % of cases in the prone position that was absent from the supine MRIs. We also documented varying grades of spondylolisthesis and facet joint subluxation resulting in significant foraminal stenosis in 26.3% of prone cases not seen from supine MRIs. CONCLUSIONS: Four patterns of pathological findings have been identified by MRI performed in the prone position. These findings were not observed in the supine position. Prone MRI can be a significant and useful tool in the diagnosis and treatment of patients with back pain refractory to treatment whose conventional supine MRIs appeared unremarkable.