The size of the vertebral canal and the significance of epidural fat in lumbar spinal stenosis.

Measurements of mid sagittal diameter (MSD) and interpedicular diameter (IPD) in patients operated on for central lumbar spinal stenosis were compared to the control group. Both groups can be matched in terms of gender and age. We found that in the stenotic patients the MSD and the IPD were smaller than in the control group, all of the measurements except the IPD in male stenotic patients was statistically different. Sagittal and axial MR images of the stenotic patients were used to evaluate the status of the posterior epidural fat which was graded as normal, small, very small and absent. All the patients were surgically treated for lumbar stenosis, imaging studies and intraoperative finding were correlated. Reduction or absence of the posterior epidural fat (PEF) by the imaging studies were found to be related to the intraoperative findings and the duration of symptoms. PEF may be used as an intraoperative indicator for optimal surgical decompression.