Neither a Lumbar Disc nor a Thoracic Disc; L1-L2 Disc Located in Region of Spine Biomechanical and Neural Transition Zone

Abstract

Introduction Although L1-L2 disc is anatomically located in lumbar region, its specific location poses a caveat to the surgeon for both conus medullaris present in this area and the great biomechanical standpoint in thoracolumbar region. Materials and Methods In our experience with this group of patients, we used trans-facet pedicle-sparing approach to care for conus medullaris. In addition, we performed short segment fusion to augment this highly demanding biomechanical region. Since the year 2008, we operated 13 cases with L1-L2 disc with this technique. Only two cases presented with severe L2 radiculopathy and the rest came with feature of cauda equine or conus problem. Axial back pain was crucial symptom in eight cases. Two patients had simultaneous disc problem in L2-L3 and one patient had T12-L1 disc protrusion. After operation, patients received Jewett hyperextension brace for 3 months. In one patient with central hard calcified disc, we performed thoracoabdominal approach and decompression from anterior. All surgery performed under high magnification of microscope and bone removal was done by powered drill. Results In six cases, decompression was performed bilaterally to reach the central portion of the disc. Pedicle screw was used for fixation in all patients. TLIF banana cage was used in five cases and spinous process bone used as interbody graft in four cases. There was no aggravation in neurological deficit and we have no problem with CSF leak or wound. Fusion achieved in all patients and axial back pain resolved successfully. Conclusion Although L1-L2 innately considered a lumbar disc, we suggest that they should be considered as thoracic disc and the surgeon should not solely rely on where the conus terminated in MRI. In this location, small traction can lead to catastrophic neurological damage; therefore, by using trans-facet pedicle-sparing under microscopic guide the cord should be decompressed by drill. In addition, to prevent neurological injury, Kerrison should not be placed under already stenotic canal. Disclosure of Interest None declared