The Evaluation of Alpha Plaster of Paris as a Osteoconductive Material in the Adult Cat Calvarium

Spontaneous new bone formation does not occur in the adult calvarium. In humans, cranial defects may require repair for brain protection, headaches or cosmetic. Over the years the search for the ideal cranioplasty material to repair such cranial defects has been extensive. We report an evaluation of alpha plaster of paris as an osteoconductive material in a cat craniectomy defect. Adult cats of either sex were anesthetized with ketamine/halothane and a 15mm biparietal craniectomy defect created. The right side was filled with alpha plaster of paris and the left served as a control. There were 4 animals in each time cohort and animals were sacrificed at 6 weeks, 6 or 12 months. The cranium was removed, fixed, stained, histologically studied and analysised for the percentage of trabecular bone formation. At all durations the control defects were bridged by proliferative fibrous tissue membrane and less than 1% trabecular bone. At six weeks the plaster of paris filled defects were either totally or nearly totally replaced by new bone formation. The plaster was completely resorbed. At 6 wks there was 28% trabecular bone which increased to 93% at 52 wks. Our experiments demonstrate the oeteoconductive potential of alpha plaster of paris in the adult calvarium. This material needs to be evaluated in humans to ascertain its potential as a biocompatible cranioplasty material.