Background: Review of the literature revealed several experimental studieson the effects of selective COX-2 inhibitors on fracture healing, but no reports were encountered regardingthe effects of these compounds on experimental heterotopic bone formation, so the present study was conducted.Material/Methods: Thirty adult male Wistar rats were divided into three groups of ten animals each. Tibialand femoral bones were collected from the rats, cleaned and demineralized, and diaphyseal parts wereimplanted in muscle pouches created in the right gluteal region, one into each rat. Group 1 receivedDFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone), a highly selectiveCOX-2 inhibitor, at a dose of 1.1 mg/kg/day. Group 2 received 2 mg/kg/day of indomethacin. The drugswere administered by oral gavage with 0.5% methyl cellulose as a delivery vehicle for eleven days, beginningon the first postoperative day. Group 3 received only methyl cellulose. Results: Thirty days after theimplantation of the demineralized bone matrix, 6/10 of DFU-treated, 9/9 of the indomethacin-treated,and 8/9 of the control rats displayed new bone formation. Conclusions: The results of this study suggestthat no form of non-steroidal anti-inflammatory drug has inhibitory effects on heterotopic bone formationin rats. In our opinion, bone formation is a quite complex process that requires several events and isregulated by several factors, so further investigations other than those using non-steroidal anti-inflammatorydrugs are required.

Keywords: Anti-Inflammatory Agents, Non-Steroidal - therapeutic use, Cyclooxygenase 2 Inhibitors - therapeutic use, Furans - therapeutic use, Indomethacin - therapeutic use, Ossification, Heterotopic - pathology