Management of exposed hydroxyapatite orbital implants

Porous coralline hydroxyapatite orbital implants have gained significant popularity for use in anophthalmic sockets. Several reports have noted increased rates of early implant exposure.

Six patients with exposure complications of primary hydroxyapatite implants after enucleation or evisceration were studied.

The hydroxyapatite implant exposures occurred 2 to 8 weeks after implantation. Magnetic resonance imaging scans with gadolinium enhancement obtained in two patients demonstrated a "cold" zone anteriorly with failure of fibrovascular ingrowth in the region of anterior exposure. Several different surgical procedures were used to regain implant coverage, including freshening the edge of the conjunctival defect and observing for spontaneous closure, burring away the anterior surface of the hydroxyapatite implant, and placing autogenous free tissue grafts of hard-palate mucosa or thin dermis-fat graft over the exposed hydroxyapatite. Repeated exposure after free graft was noted in several patients, and three of the six patients followed have an intact surface but very thin conjunctiva overlying hydroxyapatite spicules.

Although small areas of hydroxyapatite exposure (< 3 mm) may close spontaneously, larger defects do not tend to close spontaneously and should be actively managed. Based on our experience, optimal results are obtained with free autogenous tissue grafts combined with burring of the anterior hydroxyapatite surface. Steps should be taken at the time of primary implantation to minimize implant exposure, including choosing appropriately sized implants and obtaining careful coverage with good vascularized tissue under minimal tension.