AXIAL LOADING OF THE SPINE DURING CT AND MR IN PATIENTS WITH SUSPECTED LUMBAR SPINAL STENOSIS

Purpose: To evaluate the effect of compressive axial loading in imagin g of the lumbar spine in patients with clinically suspected spinal ste nosis. Material and Methods: A total of 84 patients were examined, 50 with CT (after intrathecal contrast administration) and 34 with MR. Fi rst the dural sac cross-sectional area (CSA) was determined with the p atient in the supine psoas relaxed position (PRP). Then the CSA was de termined during supine axial compression in slight extension (ACE), ob tained with a specially designed loading device. A measurement error s tudy was performed. Results. A minimum difference in CSA of 15 mm(2) b etween PRP and ACE was found to be significant. In 40/50 (80%) of CT-e xamined patients and in 26/34 (76%) of MR-examined patients a signific ant difference in CSA was found. In 25/84 (30%) of the patients there was a significant difference at more than one level.Conclusion. For an adequate evaluation of the CSA, CT or MR studies should be performed with axial loading in patients who have symptoms of lumbar spinal sten osis.