Exposure rate of hydroxyapatite spheres in the anophthalmic socket: histopathologic correlation and comparison with silicone sphere implants.

We retrospectively reviewed enucleations and secondary anophthalmic socket sphere implantations for a 3 year period. We compared the incidence of exposure of hydroxyapatite implants to the incidence of exposure of silicone implants. We found that the incidence of hydroxyapatite exposure following enucleation was 3 of 27 (11.1%), and following secondary anophthalmic socket implantation was 3 of 32 (9.4%). The incidence of silicone sphere exposure following enucleation was 0 of 48 (0%), and following secondary implantation was 1 of 30 (3.3%). The difference in exposure rate between hydroxyapatite and silicone reached statistical significance in the enucleation group (p = 0.043) and in the combined enucleation and secondary implantation group (p = 0.033), but not in the secondary implantation group when considered separately. Osteoinduction and fibrovascular infiltration were found in all hydroxyapatite specimens examined histopathologically. In the exposed implants, liquefaction necrosis of the implant occurred. In the nonexposed implant, complete fibrovascular ingrowth was noted at 7 months. We believe that the hydroxyapatite anophthalmic sphere is associated with a higher incidence of exposure and postoperative inflammation when compared to silicone anophthalmic spheres. Patient selection and technique modification may reduce the incidence of hydroxyapatite implant exposure.