A study of the hydroxyapatite orbital implant drilling procedure

The hydroxyapatite orbital implant has been introduced as a buried, integrated implant for use in the anophthalmic patient. The second stage of the procedure involves drilling the implant and inserting a motility peg that allows direct coupling of the artificial eye to the implant. Other authors have advocated an assessment of implant vascularity by imaging prior to drilling. We aimed to see whether our practice of drilling after a predetermined time interval without assessment of implant vascularity would result in a higher complication rate. We also aimed to determine how successful the drilling procedure was in improving both the motility and the stability of the artificial eye.

The notes of 41 consecutive patients who underwent drilling were studied to determine the time interval between implantation with a hydroxyapatite sphere and drilling, the nature of any complications and any further surgical procedures undertaken. A postal questionnaire was sent to all patients asking them to grade the motility of their implant before and after drilling, and to state whether or not there had been any improvement in the stability of their artificial eye.

The most frequent complication encountered was extrusion of the motility peg, which occurred in 3 patients. A total of 5 patients required redrilling. There was an 80% response rate to the questionnaire. Ninety-one per cent of patients felt that there had been an improvement in the motility of their artificial eye and 76% felt that the stability of their artificial eye had been improved.

Pegging of the hydroxyapatite implant improves both the motility and the stability of the artificial eye in the majority of cases. Complications are infrequent and minor. If sufficient time is allowed after implantation for full implant vascularity to occur, it is not necessary to perform imaging studies. This practice does not result in an increase in complications, and significantly reduces the expense of the procedure.