Radiopharmaceutical isotopes are widely used clinically to detect tumors of
osteogenic origin. One example is Technetium-99m methylene diphosphonate (
Tc-99m-MDP). When viewed with a gamma camera, the concentration of the isot
ope (increased gamma activity) indicates an area of increased bone activity
. This technology provides an opportunity to measure bone growth around imp
lants in vivo. The purpose of this study was to measure Tc-99m-MDP activity
around titanium alloy implants placed in the tibiae of rats. Some implant
sites were treated with a growth factor; other sites served as controls. Th
e hypothesis tested was that implants placed with a growth factor would hav
e greater associated Tc-99m-MDP activity. Twelve adult mate Sprague-Dawley
rats were anesthetized and surgical access to the medial proximal tibiae wa
s obtained. Titanium alloy screw implants were placed in six animals along
with 65 mug of acidic fibroblast growth factor (FGF-I); the other six anima
ls received implants only and served as controls. After five days, rats wer
e injected with 1500 mu Ci of Tc-99m-MDP After 3 hours, rats were imaged wi
th a gamma camera. The Tc-99m-MDP intensity associated with each implant wa
s quantified and the means for each group were compared using ANOVA. Implan
ts treated with FGF-1 demonstrated significantly more Tc-99m-MDP activity t
han implants alone. This suggests that Tc-99m-MDP analysis may be a useful
tool for determining bone growth around implants in laboratory animals in v
ivo.