Rate of vascularization and exposure of silicone-capped porous polyethylene spherical implants: an animal model.

PURPOSE: This pilot study examines the rates of exposure and fibrovascular ingrowth of silicone-capped, porous, polyethylene orbital implants in the New Zealand white rabbit animal model. METHODS: Unwrapped, silicone-capped, porous, polyethylene orbital spheres were implanted in 16 enucleated rabbit orbits. Four implants were removed at 3, 6, 9, and 12-month intervals and submitted for histopathologic analysis. A board-certified pathologist reviewed and graded vascular ingrowth, inflammation type, and severity for all specimens. RESULTS: Fibrovascular ingrowth in the center of all implants occurred as early as 3 months. No fibrovascular ingrowth occurred at the interface between the silicone cap and the porous polyethylene implant. The overlying Tenon's and conjunctival tissues remained intact without significant host inflammatory response. No implant exposure occurred at any time point. CONCLUSIONS: Silicone-capped porous polyethylene orbital implants appear to offer an inexpensive, easy-to-manufacture implant that resists exposure without the need for a wrapping material and achieves successful biointegration soon after implantation.