Microsurgical Decompression of Lumbar Spinal Stenosis: Two Methods

Two operative procedures are described for microsurgical decompression of lumbar spinal stenosis with narrow canal syndrome: (1) a unilateral approach that achieves bilateral decompression by undercutting the midline structures to access and decompress the contralateral side, and (2) a midline approach which after removing the spinous processes, drills out the remaining bases of the processes and adjacent laminae through a relatively narrow midline exposure with minimal retraction of the paraspinous muscle masses. The former was used on acquired spinal stenosis which was primarily ligamentous and degenerative without marked congenital stenosis. The latter was used for decompression of more severe lumbar spinal stenosis that was associated with pronounced congenital narrowing of the lumbar spinal canal in addition to degenerative changes.

The unilateral approach for bilateral ligamentous decompression was achieved via an extension of laminotomies which drilled away the subiacent bases of spinous processes and allowed resection of hypertrophied ligamentum flavum in the midline and on the opposite side of the canal. This was done in such a way that the structural integrity of spinous processes was not compromised.

Visualization of the opposite side of the spinal canal was then possible by angulation of the operating microscope and lateral tilt of the operative table. In some cases one can even drill the medical aspect of contralateral facet joints if required. A 5.5 mm cutting burr on an Ultrapower Hall drill was used for both the midline and unilateral approached. A diamond burr was used whenever drilling a contralateral oteophyte from a unilateral exposure. Canal ligaments were removed with bone punches and ronguers.

These limited surgical exposures produced less post operative pain, reduced hospital stays, and avoided the potential for destabilization with traditional procedures. The downside of these methods was a modest increased in operative time, more difficult anatomical orientation when accessing the contralateral canal via a unilateral exposure, and an increased rish of dural laceration from the drill. Eight cases have been performed with good to excellent outcomes achieved in 88%.