Assessment of neuroforaminal decompression in degenerative spinal stenosis.

Surgical decompression of spinal stenosis is a balance between adequate removal of bone and soft tissue for an effective decompression of neural structures and a sufficient retention of bone to maintain mechanical stability of the spine. To develop an objective, reproducible technique for the assessment of neuroforaminal decompression in the adult lumbar spine, facet sparing laminectomies were performed from L1-S1 on the lumbar spines of 59 human cadavers. A series of semirigid probes in 0.5-mm increments were passed into each successive intervertebral foramen bilaterally, beginning at L2-L3. The minimum space available for the nerve root within the foramen of the lumbar spine is 3.5 mm at L2-L3, 3.9 mm at L3-L4, 4.3 mm at L4-L5 and 5.1 mm at L5-S1, as determined by three independent observers. There were no significant differences in interobserver or intraobserver measurements. There were no complications related to passage of the probes. This study provides a method for the intraoperative determination of the adequacy of neuroforaminal decompression.