Application of polyvinyl alcohol hydrogel membrane as anti-adhesive interposition after spinal surgery.

Abstract

Three inflammatory and adhesive changes inside the spinal canal were analyzed histopathologically in cats. To investigate the usefulness of a polyvinyl alcohol hydrogel sheet as an interposition over the dura to prevent inflammatory and adhesive reaction after laminectomy. A major concern after laminectomy is scar tissue formation that may result in extradural compression or make subsequent surgery to the same area difficult and hazardous. Wide laminectomy was performed at L5 in 30 adult cats. The dura was covered with a polyvinyl alcohol hydrogel sheet, free fat graft, or without interposition as a control. Animals were killed at 3 or 12 weeks. In the control group, adhesion of the exposed dura was apparent. 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 migrated into the interstitial space. In the polyvinyl alcohol hydrogel group, only a thin synovium-like layer was formed around the polyvinyl alcohol hydrogel sheet. Polyvinyl alcohol hydrogel is made of water and alcohol, and has been shown to be nontoxic to tissues. This is permeable to low molecular weight, but impermeable to large cells such as fibroblasts. Thus, the polyvinyl alcohol hydrogel sheet prevents migration of inflammatory cells and subsequently reduces intraspinal canal scar tissue formation and adhesive reaction. Other beneficial properties are extreme elasticity and low friction, which eliminate mechanical reaction to the spinal cord. The polyvinyl alcohol hydrogel sheet is believed to be useful in eliminating scar tissue formation and does not interfere with the dynamic gliding movement of the spinal cord and nerve roots.