Ipsilateral decompression on one side
After the access has been created, the bony structures are exposed. It may be helpful to start decompression at the caudal end of the descending facet. Depending on the pathology, decompression is then commenced with resection of parts of the medial descending facet, the cranial and caudal lamina, and the ligamentum flavum. The extent of decompression generally continues cranially at least until the tip of the ascending facet and caudally to half of the pedicle. The medial portions of the ascending facet and the ligamentum flavum are then resected until sufficient decompression of the neural structures can be clearly seen - cranially, caudally and laterally. In the case of a central stenosis, the ligamentum flavum generally needs to be resected medially to the midline. Finally, it may be necessary to remove protruding annulus parts and osteophytes in the ventral epidural space
Contralateral decompression in over-the-top technique
If bilateral symptoms occur with a central stenosis, a unilateral approach is carried out with "over-the-top" access using the undercutting technique to the opposite side. For this purpose, bone in the ventral area of the spinous process is resected until the contralateral side can be accessed dorsally up to the dura of the spinal cord. If possible, the ligamentum flavum is initially left in place to protect the dura and bony decompression is again carried out by laminotomy and partial facetectomy. The ligamentum flavum is then completely resected. Finally, the contralateral recess needs to be extended. The decompression is completed when the dura and the spinal nerves have been clearly decompressed.