The chronic local effects of sublaminar wires. An animal model.

An animal model was established to determine the chronic effects of sublaminar wires. Nine dogs were instrumented with sublaminar wires, sacrificed at intervals up to 155 days, then subjected to wire removal under cineradiographic myelography and histologic analysis. Common dural sac indentation by the wires during extraction averaged 47% of the total myelographic column width, with no correlation to time implanted. Epidural, subdural, and intramedullary hemorrhage, epidural adhesions, dural lacerations, cord indentations, and neural damage were all present with no correlation to time implanted. Dural thinning was more pronounced in later specimens. These data suggest that sublaminar wires are not innocuous to the dural sac and its contents in this canine experimental model.