Compartmentalized bone regeneration of cranial defects with biodegradable barriers--effects of calcium sodium phosphate surface coatings on LactoSorb.

Abstract

In bony defects of the cranium, bone healing may be complicated by prolapse of surrounding tissue into the defect. This tissue acts as a potential obstruction to the migration of osteogenic cells, resulting in impaired bone formation. It has been shown in previous studies that when a membrane composed of resorbable polymers (LactoSorb) is placed over a cranial bone defect, it inhibits connective tissue from entering the wound and improves the rate and quality of the bony regenerate. This study is an extension of this work and specifically evaluated the effects of differing calcium-based surface coatings on membrane-covered cranial defects in the rabbit model. In non-critical size, full-thickness defects of the mature rabbit calvarium, four differently treated LactoSorb membranes were evaluated in each animal model over a 1-year postoperative period. The surface coatings (three treated, one untreated) consisted of a base-powdered material of calcium sodium phosphate (Osteostim, EBI, NJ), which were applied by different methods (pressed, brushed, one-sided versus two-sided). Evaluation consisted of cross-sectional histologic assessment of the cranial detects determining the quantitative bony fill and the presence of residual polymer material and calcium sodium phosphate. This study produced the following findings: (1) cranial defect regeneration occurs faster with calcium-coated membranes and is complete by 3 months; (2) no difference could be seen between the different methods of calcium sodium phosphate coating; (3) the calcium sodium phosphate coatings did not inhibit resorption of the biodegradable membranes for those systems that had coatings on one side; however, systems completely covered showed delayed resorption; and (4) the calcium sodium phosphate coatings did not produce any inflammatory reactions. These findings suggest that, in addition to inhibiting connective tissue from entering the wound site, the calcium coatings on resorbable devices may have beneficial effects in selected clinical conditions, especially in conditions where faster bone regeneration is necessary.