Clinical Study of Vacularization of Hydroxyapatite Ocular Implants by 99mTc-MDP Bone Scan

ABSTRACT

Hydorxyapatite ocular implants, which are used to replace the volume of the orbit following enucleation and evisceration, allow the artificial eye to move. For this advantage, drilling is required to integrate peg into implant for transfer of motion. The earlier drilling, the earlier good results in cosmesis, but it should be done in the conditon of complete vascularization to reduce infection and exposure. To evaluate the proper timing for drilling and the difference of vascularization rate between standard eevisceration(group A) and modified evisceration(group B), we attempted to evaluate implant vascularization by using 99mTc-MDP bone scan prospectively at various intervals from 10 to 23 weeks(6 patients at 10-12 weeks, 29 patients at 13-16 weeks, 31 patients at 1720 weeks, and 7 patients as 21-23 weeks) after implantation. In 7 out of 73 patients postcontrast MRI was performed on the same day of 99mTc-MDP bone scan, we compared the degree of enhancement with that of uptake in each patients. In group A the ratio of complete graft vascularization was seen in 0% at 1012 weeks, 33% at 13-16 weeks, 50% at 17-20 weeks, and 67% at 21-23 weeks. On the other hadnd in group B it was seen in 50% at 10-12 weeks, 55% at 13-16 weeks, 55% at 17-20 weeks, and 75% at 21-23 weeks. It was increased with time. The time of complete vascularization was not different between group A and B. In 7 patients studied with both 99mTc-MDP bone scan and MRI, the degrees of vascularization were very similar on the two examinations in each patients. We would like to suggest that it is proper to perform 99mTc-MDP bone scan at 21 weeks after implantation regardless of surgical methods. 99mTc-MDP bone scan is more economic than postcontrast MRI for evaluation of complete vascularization in hydroxyaptite implant.