Bs. Sires et al., HISTOLOGICAL AND RADIOLOGICAL ANALYSES OF HYDROXYAPATITE ORBITAL IMPLANTS IN RABBITS, Ophthalmic plastic and reconstructive surgery, 11(4), 1995, pp. 273-277
To date, only anectodal clinical data exist pertaining to the histolog
ical changes of hydroxyapatite within an enucleated socket. This study
was conducted to determine the histological and radiological changes
in a coralline hydroxyapatite sphere placed into the central socket, i
n a controlled fashion. Rabbits underwent simple enucleation with impl
antation of an autologous sclera-wrapped hydroxyapatite spheres with e
xtraocular muscle reattachment. Preoperatively, the mineral density of
each sphere was determined using quantitative computed tomography (CT
) that was repeated 2- and 6 weeks postoperatively. The implants were
harvested at 2- and 6 weeks and submitted for light and electron micro
scopic analysis. The results demonstrated a uniform influx of fibrovas
cular tissue that did not reach the center of the implant, even at 6 w
eeks. A marked mixed-cell inflammatory response was noted at the inter
face between the fibrovascular tissue and the hydroxyapatite. Giant ce
lls were noted only at the scleral windows. This study demonstrated th
at the early response to hydroxyapatite implants was fibrovascular ing
rowth with mixed-cell inflammation. These histological observations co
rrelated with findings observed with quantitative CT. Quantitative CT
appears to be an ideal modality for observing the early temporal tissu
e density changes in hydroxyapatite implants.