Effect of teriparatide on bone regenerate after distraction osteogenesis

Objective: To determine the effect of teriparatide on new bone formation in a rat model of distraction osteogenesis. Methods: The experimental study was conducted at the Aga Khan University Hospital, Karachi, in November-December 2010, and comprised male Sprague-Dawley rats weighing 250gm each who were allocated to two treatment groups, teriparatide and saline, both given subcutaneously for 7 weeks. Femoral distraction was done for 3 weeks at the rate of 0.4mm/day, followed by a further 4 weeks for consolidation. New bone formation was assessed using X-ray scoring system, bone densitometry and histology. Results: The 12 rats in the study were divided into two groups of 6(50%) each. All rats in the teriparatide group showed new bone formation whereas bone formation was present only in 2(33.3%) rats in the saline group. Bone densitometry showed that area (size) of the new bone formed adjacent to the margins of the osteotomy site as well as the total bone mineral content of the new bone was significantly higher (p<0.05) in the teriparatide group. Histological analysis showed larger but statistically insignificant (p>0.05) area of woven and trabecular new bone in the teriparatide group. Conclusion: The results suggested a promising role of parathyroid analogue therapy in distraction osteogenesis for promoting bone formation and consolidation. This may have strong clinical implications in cases of limb lengthening and bone transport.