Late infection of hydroxyapatite orbital implants

Background: Exposure and minor complications of hydroxyapatite orbital impl ants are common. infection appears to be rare and fibrovascular ingrowth in to hydroxyapatite implants may make infection and extrusion less likely tha n with other types of orbital implant. Methods: We describe three cases of chronic low-grade infection of hydroxya patite implants, occurring late after apparently uncomplicated surgery, wit h tiny or inapparent areas of conjunctival loss or exposure. Results: Two of the three cases grew Staphylococcus aureus on culture. All three implants ultimately needed to be removed. A characteristic histologic al pattern was seen, with abrupt transition between vascularized and absces sed implant. Conclusions: Chronic infection of hydroxyapatite implants can occur late, i n the absence of large conjunctival defects, or other obvious risk factors, While exposure of the implant to pathogens through a breach in the conjunct iva may have been a factor; it appeared that the infection may have arisen in an avascular portion of the implant prior to the conjunctival breakdown in one or more of these cases.