A biomechanical evaluation of internal lumbar laminoplasty: the preservation of spinal stability during laminectomy for degenerative spinal stenosis.

The long-term success of surgical management of spinal stenosis by decompressive lumbar laminectomy is predicated partly by the maintenance of intervertebral stability. Excessive bone removal, especially of the pars interarticularis, may predispose the spine to iatrogenic segmental instability and spondylolisthesis. Removal of too little bone may be inadequate to relieve stenotic or radicular symptoms. Wide decompression with concomitant arthrodesis has been advocated, but arthrodesis compounds the surgical complexity and increases the risks of surgical treatment. Internal lumbar laminoplasty obviates the problem of too little or too much bone removal in the surgical management of spinal stenosis. The spinal canal is enlarged internally by an undercutting facetectomy performed through a narrow central laminectomy. The pars interarticularis is left completely intact. Twenty five adult human cadaveric spinal units were subjected to biomechanical testing following hemilaminectomy, total laminectomy, internal laminoplasty, partial facetectomy, or disk transection and internal laminoplasty. Analysis was performed after video and computer acquisition of data from specimen testing on an Instron machine. Internal laminoplasty demonstrated more intrinsic stability than the other surgical procedures.