ROOT DECOMPRESSION AND SEGMENTATION IN THE LUMBAR SPINE

Abstract

We compared magnetic resonance imaging (MRI) scans and plain antero-posterior (AP) and lateral radiographs of 100 randomly selected patients in order to detect segmental abnormalities of the lumbar spine. We started by identifying those who appeared to have a segmental defect of the lumbar spine on MRI scan. We then checked all 100 plain radiographs to detect the true rate of segmental abnormality. We detected 17 patients with a segmental abnormality that correlates well with other studies. We believe that MRI scanning alone is not sufficient to detect reliably all segmentation defects in the lumbar spine, and that a plain lateral and an AP x-ray is also required. Of those who do have a segmentation disorder we have identified a sub-group who are at risk of surgery at the wrong level, if the correct pre-operative work-up is not performed. The difficulty will occur when a segmental abnormality is present (as determined by plain radiographs) and it is missed by MRI scan, and plain films are not taken, and the correct level is determined by counting upwards from the lumbosacral take-off angle using the image intensifier in theatre. We believe that all patients undergoing nerve root decompression should have an AP and lateral plain film and an MRI scan as well as pre-operative image intensification in theatre. Although the number of patients that would be affected by this is small, the consequences of operating on the wrong level are well recognised and can be avoided by being aware of the potential problem and by adhering to the above recommendations.