INTRAOSSEOUS INFUSION OF PROSTAGLANDIN E(2) PREVENTS DISUSE-INDUCED BONE LOSS IN THE TIBIA

We investigated whether intraosseous injection of prostaglandin E(2) w ould preserve tibial bone mass in the skeletally unloaded limb of a la rge animal model. Skeletal unloading of one rear limb was produced by unilateral Achilles tenectomy in the goat. Prostaglandin E(2) was inje cted at 0.5 or 1.0 mg (1 ml of volume) twice daily, beginning on day 7 and continuing for 10 days, through an implant that had been surgical ly placed in the proximal tibial metaphysis. Thirty-five days after su rgery, the tibiae were harvested for measurement of static and dynamic bone parameters and mechanical characteristics using transmission ult rasound. Prostaglandin E(2) produced a dose-dependent increase in the formation of woven new bone at all bone envelopes. The 1.0 mg dosage p revented and partially reversed the effects of skeletal unloading and added new bone (p < 0.05) compared with the unloaded tibiae. Because p rostaglandin E(2) increased both bone formation and resorption and the new bone produced was primarily woven bone, the material properties o f the tibiae infused with prostaglandin E(2) did not increase signific antly during the study compared with the unloaded and weight-bearing t ibiae.