Abstract
A major concern after laminectomy is formation of scar tissue, which may result in extradural compression or make subsequent surgery to the same area difficult and hazardous. The main purpose of this study was to investigate the usefulness of a polyvinyl alcohol hydrogel (PVAH) sheet as an interposition over the dura to prevent inflammatory and adhesive reaction after laminectomy. Wide laminectomy was performed at L5 in 60 adult cats. The dura was covered with a PVAH sheet of a free hyplen fat graft or was left without any interposition as a control. Animals were killed at 3 or 12 weeks or at 1 year. In the control group, adhesion of the exposed dura was apparent. Formation of thick fibrous connective tissue was observed between the dura and the paravertebral muscles. In the fat graft group, the dura was separated from the scar tissue by living grafted fat. However, the dura was adherent to the grafted fat and fibroblasts had migrated into the interstitial space. In the PVAH group, only a thin synovium-like layer had formed around the PVAH sheet. PVAH is made of water and alcohol and has been shown to be nontoxic. It is permeable to low molecular weight cells but impermeable to large cells, such as fibroblasts. Thus, the PVAH sheet prevents migration of inflammatory cells, and, subsequently, reduces formation of scar tissue and adhesive reaction in the intraspinal canal. Other beneficial properties are extreme elasticity and low friction, which eliminate mechanical reaction to the spinal cord. It is felt that the PVAH sheet is useful in preventing formation of scar tissue and does not interfere with the dynamic gliding movement of the spinal cord and nerve roots.
