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September 1997

Clinicopathological Correlation of Technetium Bone Scan in Vascularization of Hydroxyapatite Implants: A Primate Model

Author Affiliations

From The Wilmer Ophthalmological Institute (Drs Pacheco, Iliff, and Green and Mr D'Anna) and the Division of Nuclear Medicine, Department of Radiology (Drs Civelek and Natarajan), The Johns Hopkins University School of Medicine, Baltimore, Md.

Arch Ophthalmol. 1997;115(9):1173-1177. doi:10.1001/archopht.1997.01100160343013

Objectives:  To report the histopathological and bone scan characteristics of the stages of hydroxyapatite fibrovascular integration and to consider the implications for the timing of peg drilling in a primate model.

Design:  Three monkeys received hydroxyapatite implants covered only anteriorly with a fascia lata button to which the rectus muscles were sutured. Weekly bone scans were evaluated quantitatively and qualitatively. The orbits were harvested at 2,4, and 8 weeks and examined histopathologically.

Results:  Quantitatively, the implant's technetium uptake increased, then reached a plateau by 4 weeks. Peripheral uptake was present on the images and histologically at 2 weeks. When bone scan images suggested complete vascularization by the fourth week, the implant was 99% vascularized histologically. Completion of vascularization was ascertained at 8 weeks, without further discernible changes in the bone scans.

Conclusions:  The technetium bone scan is sensitive to the vascularization of the hydroxyapatite implant and discerns when complete vascularization is approached. This primate study models closely the clinical findings we have recently reported. We advocate at least a 4-week interval between the time the bone scan suggests full vascularization and peg drilling.

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