The natural history of alloplastic implants in orbital floor reconstruction: an animal model.

We developed a new animal model to recreate the condition of an open fracture in communication with the maxillary sinus. We then studied wound healing of the sinus wall structures following fracture in the presence of an alloplastic implant. This model is designed to simulate the alloplastic repair of an orbital floor fracture in humans. The New Zealand White rabbit was used as the animal model. Standardized 8-mm defects were made bilaterally in the maxillary sinuses to include bone and mucosa in 21 rabbits. Two different implants were placed in the soft-tissue pockets to obturate the defects, exposing one surface of the implant to the open sinus. Medpor porous polyethylene and silicone implants were compared. Animals were killed at 1, 2, 3, and 4 weeks and at 2, 4, and 5 months after implantation. Gross examination of the specimens for the amount of mucosal closure and implant tissue fixation was performed. Histological sections were evaluated for bone and soft-tissue morphology juxtaposed to the implant. Complete closure of the mucosal defect was demonstrated with both types of implants. Medpor implants showed both vascular and soft-tissue ingrowth into its pores by week 1. Bone ingrowth was seen by week 3. Closure of the Medpor obturated defects occurred more rapidly than in the silicone group (p < 0.004 at week 4). The Medpor implants demonstrated bone and soft-tissue fixation, and mature overlying mucosa was reconstituted over the defects. Silicone implants demonstrated a fibrous tissue reaction within 1 week of implantation and they never became fixed to bone or soft tissue.(ABSTRACT TRUNCATED AT 250 WORDS)