Structural Changes in Thoracolumbar Disks Following Lateral Fenestration A Study of the Radiographic, Histologic, and Histochemical Changes in the Chondrodystrophoid Dog

Abstract

Lateral fenestrations of intervertebral disks T12–13 through L2–3 were performed on 16 1‐year‐old chondrodystrophoid dogs. The disks of five dogs were fenestrated by removing the core of disk material with a 20 gauge spinal needle, six were fenestrated in the same manner with a 14 gauge spinal needle, and five were fenestrated with a 14 gauge spinal needle and a tartar scraper. Forty‐two of 48 disks had radiographic evidence of narrowing following surgery. Microscopic examination of the disks indicated that the nucleus pulposus was nonreactive tissue and that fenestration did not incite an inflammatory response that resulted in dissolution of the nucleus pulposus. Results of histochemical analyses of the fenestrated disks were not different from those of control disks. The only effects observed during a 24 week period following fenestration were disruption of the annulus fibrosus and nucleus pulposus by the fenestration device, removal of varying amounts of the nucleus pulposus, and vascular and fibrous tissue invasion of the lateral annulus fibrosus. These findings suggest that the effectiveness of fenestration is governed by the amount of nucleus pulposus removed.