A preliminary report of percutaneous craniofacial osteoplasty in a rat calvarium.

OBJECTIVE: To evaluate the potential for injectable, permanent bone augmentation by assessing the biocompatability and bioactivity of subperiosteal hydroxylapatite (Radiesse) deposition in a rat model. STUDY DESIGN: Randomized controlled animal model METHODS: Fourteen adult Sprague Dawley rats were injected in the parietal skull with 0.2 ml of hydroxylapatite (10 animals) or a carrier gel control (4 animals), using a subperiosteal injection technique on the right and a subcutaneous injection technique on the left. At 1, 3, and 6 months, 3 rats (1 negative control, 2 variables) were sacrificed and calvaria were harvested. At 12 months, the remaining 5 rats were sacrificed. After each harvest, the specimens were processed and then examined under both light and polarized microscopy for new bone growth at the injection sites. RESULTS: The inflammatory response was limited with both hydroxylapatite and carrier injections. Injectables were still present 12 months after the injection. New bone formation was only seen when the injection was located deep to a disrupted periosteum The odd of new bone formation was 48.949 times higher (95% CI (2.637, 3759.961), p = 0.002) with subperiosteal hydroxylapatite injections compared to all other combinations of injection plane and injectable. CONCLUSION: This preliminary report of subperiosteal hydroxylapatite (Radiesse) injection in a rat model has verified the biocompatibility of injectable hydroxylapatite at the bony interface and suggests the potential for new bone formation