Intraosseous infusion of prostaglandin E₂ prevents disuse-induced bone loss in the tibia

We investigated whether intraosseous injection of prostaglandin E₂ would preserve tibial bone mass in the skeletally unloaded limb of a large animal model. Skeletal unloading of one rear limb was produced by unilateral Achilles tenectomy in the goat. Prostaglandin E₂ was injected 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 surgically placed in the proximal tibial metaphysis. Thirty-five days after surgery, the tibiae were harvested for measurement of static and dynamic bone parameters and mechanical characteristics using transmission ultrasound. Prostaglandin E₂ produced a dose-dependent increase in the formation of woven new bone at all bone envelopes. The 1.0 mg dosage prevented and partially reversed the effects of skeletal unloading and added new bone (p<0.05) compared with the unloaded tibiae. Because prostaglandin E₂ increased both bone formation and resorption and the new bone produced was primarily woven bone, the material properties of the tibiae infused with prostaglandin E₂ did not increase significantly during the study compared with the unloaded and weight-bearing tibiae.