Synthetic hydroxyapatite-based integrated orbital implants: a human pilot trial.

PURPOSE: Orbital implants are used as fillers following enucleation or evisceration surgeries to replace the lost volume for better cosmesis and motility of the artificial eye. Over the last decade porous hydroxyapatite (HAp) implants derived from the naturally occurring corals, are increasingly used. Recently synthetic HAp-based implants have been introduced. After fibrovasculrisation they have the added advantage of being directly integrated with the artificial shell, thereby increasing the motility to a great extent. The current study, evaluated the efficacy of two different models of synthetic HAp with 75% porosity and pore sizes ranging from 100 to 300 mm. METHODS: Synthetic HAp powders were prepared with a novel wet chemical route. Two models of porous orbital implants with the characteristic designs for both evisceration and enucleation surgery were developed, characterised and implanted to consecutive 25 human subjects, 17 following evisceration, and 8 following enucleation. The postoperative performances of these implants were evaluated in respect to the degree of volume replacement (implant + prosthesis), presence/absence of lagophthalmos and lower eye-lid laxity, status of socket and fornices. Magnetic resonance imaging assessed the stability of the implants within the socket and progressive fibro-vascularisation within the porous scaffold as a function of time. Finally, motility of the implants as well as the prostheses (horizontal movements by Lister Perimeter) and subjective cosmetic results (qualitative) were also evaluated. RESULTS: During the 2.5 years of follow-up study, no significant postoperative complications were noticed. One case, showed an anterior implant exposure of 3-4 mm, and was managed with donor scleral patch graft and one case of conjunctival thinning was corrected by re-suturing the conjunctival dehiscence. Fourteen of the 25 patients had a very good movement of the prostheses (> 20 degrees horizontal movement) and the other 11 patients had a fair motility (10 - 20 degrees). The degree of volume replacement (with prosthesis) was found to be very good in 21 patients and fair in other 4 patients. All patients reported cosmetic satisfaction. CONCLUSION: Synthetic HAp-based integrated orbital implants with this modified design were found clinically safe and cosmetically acceptable.