Influence of nonbiologic implants on laminectomy membrane formation in dogs
Authors: Trotter E. J. , Crissman J. , Robson D. , Babish J. 
Published: February 2025

The effects of various surgical implants, spinal cord hypothermia, and glucocorticoid administration on formation of the laminectomy membrane were evaluated in 32 preconditioned chondrodystrophoid dogs. Modified dorsal laminectomies and full-length durotomies, from T12 to L1, were performed on all dogs. Dogs were allotted to 2 groups. Group-1 dogs (n = 20) were further allocated to 4 subgroups (a, b, c, and d) consisting of 5 dogs each. Group-1a dogs received no implant, group-1b dogs had absorbable gelatin sponges implanted, group-1c dogs had absorbable gelatin films implanted, and group-1d dogs had absorbable gelatin sponges and absorbable gelatin films implanted. Daily neurologic examinations permitted correlation of neurologic dysfunction with secondary spinal cord compression in those dogs in which it developed. The influence of these implants on laminectomy membrane formation and dural healing was assessed by gross and microscopic evaluation of transverse sections of the vertebrae and spinal cord after euthanasia of one member of each subgroup at 1, 2, 4, 8, and 16 weeks after surgery.

Group-2 dogs (n = 12) were further allotted to 3 subgroups (a, b, and c) consisting of 4 dogs each. One dog in each group-2 subgroup underwent the same surgical procedures described for the group-1 subgroups (ie, 4 procedures/group-2 subgroup). The additional effects of 3 conventional supportive techniques (selective regional spinal cord hypothermia, glucocorticoid administration, or spinal cord hypothermia and glucocorticoid administration) on laminectomy membrane formation and on immediate postoperative recovery were examined in groups 2a, 2b, and 2c, respectively. Neurologic examinations were performed daily until this time. All dogs in group 2 were euthanatized 1 week after surgery for gross and microscopic examination of transverse sections of the vertebrae and spinal cord.

Qualitative histopathologic effects of the different implants and supportive techniques on formation of the laminectomy membrane were determined. Statistical analysis of the degrees of secondary spinal cord compression was performed in group-1 dogs by measuring and comparing ratios of the vertical to the horizontal diameters or the transverse spinal cord sections from locations within (T12 to L1 and out of (T11, T11-12, L1-2, and L2) the region of surgical intervention. The vertical/horizontal diameter ratios measured from transverse sections from T11 to L2 in size-matched, untreated control dogs formed the standards for a mean roundness index of the spinal cord in the various anatomic locations of the vertebral column.

A significant difference was not detected between measurements from dogs in which there was no implantation and those from dogs in which absorbable gelatin sponge was implanted, or between measurements from dogs receiving absorbable gelatin film and those from dogs receiving both absorbable gelatin sponge and absorbable gelatin film. There were, however, significant (P < 0.05) differences between measurements from dogs that did not receive an implant and those from dogs in which absorbable gelatin film was implanted, between dogs that did not receive an implant and those in which absorbable gelatin sponge/absorbable gelatin film was implanted, between dogs in which absorbable gelatin sponge was implanted and those in which absorbable gelatin film was implanted, and between dogs in which absorbable gelatin sponge was implanted and dogs in which absorbable gelatin sponge/absorbable gelatin film was implanted. No implant or absorbable gelatin sponge implantation resulted in less compression of the spinal cord than did the other implants.

The ancillary supportive techniques resulted in readily identifiable microscopic changes in the healing patterns of the laminectomy defects, but did not significantly alter the spinal cord compression or the transient postoperative neurologic deficits.