Supine vs. Upright Weight Bearing MRI in the Evaluation of Patients With Lumbar Spondylolisthesis

Detailed Description Spondylolisthesis is a spinal condition in which one vertebral body has slid forward in relation to the vertebrae below and is sometimes associated with spinal instability. Lumbar spondylolisthesis is a relatively common problem and is generally diagnosed from radiographs. MRI is often used to evaluate the condition further and to determine if there is nerve root compression involved. One potential disadvantage with traditional MRI to evaluate spondylolisthesis is imaging is performed with the patient lying supine in the scanner. This creates a potential for the superior vertebra to slide posteriorly so that the extent of the slip may not be fully appreciated, if seen at all. Use of upright weight bearing MRI provides the opportunity to image the spine in the position that patients are most likely to experience symptoms and is similar to standing radiographs.

MRI Acquisition: Each patient will undergo MRI scanning in the supine and weight bearing positions during the same imaging session. If it is determined that a patient who has consented to participate in the study should not have an MRI made due to safety concerns (such as metallic implant or other contraindication to MRI not identified during recruiting), they will be discontinued from the study and another patient recruited to fulfill the planned number of images available for analysis.

The MRI procedure will be standard lumbar spine scanning protocol using the Esaote G-scan, an open unit. Patients will be scanned supine and then the unit rotated to 81 degrees from horizontal for the weight bearing scan. Immediately after each scan, the patient will complete visual analog scales (VAS) assessing back and leg pain.

Researcher(s) performing image assessments will be blinded to the position in which scans were made. Data to be recorded for each image is the Meyerding scale (1-4 scale rating the severity of the spondylolisthesis), amount of slip (mm), anterior and posterior disc space height (mm), foraminal area, anteroposterior (AP) distance at the most narrow part of the foramen, and disc space angulation. Area of the spinal canal and AP distance across the canal will be measured from axial images. The facet fluid sign, associated with spinal instability, will be assessed from axial MRI views using a 3-point scale with "none" indicating no evidence of fluid in the left or right facet joints; "possible" if there is some suggestion of fluid in the joints; or "definite" if there is at least a 2 mm wide layer of hyperintensity within either joint bilaterally at the level evaluated. Additionally, the width of the fluid fill of the facet joint taken perpendicular to the apparent joint line, and the largest value recorded as effusion size.

Clinical Assessments: VAS separately assessing back and leg pain will be completed immediately after the supine scanning and again immediately after weight bearing scanning. Analysis will be conducted to determine if differences in pain correlate with changes in images taken in the two positions.