Rate of vascularization of coralline hydroxyapatite spherical implants pretreated with saline/gentamicin, rTGF-beta...

Several authors have reported significant exposure rates using the hydroxyapatite orbital implant in the treatment of the anophthalmic socket. Histologic studies by ourselves and others have suggested that lack of fibrovascular ingrowth into the implants may contribute to conjunctival breakdown and exposure. Recently, much attention has been given to angiogenic factors, such as rTGF-beta 2 and those found in plasma, in accelerating wound healing and fibrovascular ingrowth. This pilot study compares the rate of vascularization of hydroxyapatite orbital implants pretreated with plasma, rTGF-beta 2, and a saline/gentamicin solution with that in untreated controls ina population of New Zealand albino rabbits. Hydroxyapatite orbital spheres were implanted subcutaneously and in enucleated orbits. Untreated implants were used as a control. Implants pretreated with plasma, rTGF-beta 2, and a saline/gentamicin solution were removed and examined histologically at weekly intervals for the first 3 weeks after implantation. Histologic studies demonstrated that the rate of vascularization significantly increased between 2 and 3 weeks postoperatively in all study groups. Pretreating the implants with rTGF-beta 2 in phosphate buffered solution (PBS) or autogenous plasma did not significantly increase the rate of vascularization in comparison with controls at weeks 1 and 2. However, pretreating the implants with a saline/gentamicin solution or PBS alone was associated with an increased rate of vascularization at weeks 2 and 3. No statistically significant difference in vascularization was noted between the subcutaneous and orbital implants at any week. Hydroxyapatite implants pretreated with saline/gentamicin or phosphate buffered solutions underwent more rapid vascularization at weeks 2 and 3 in comparison with controls. Additionally, all groups were noted to have a more rapid rate of ingrowth between weeks 2 and 3 than between weeks 1 and 2. Plasma and rTGF-beta 2 (at the dose used) did not significantly alter the rate of vascularization of hydroxyapatite implants during the first 2 to 3 weeks. The significance of these findings is discussed.