Effects of Intermittent Low-Dose Parathyroid Hormone Treatment on Rapid Mandibular Distraction Osteogenesis in Rabbits.

PURPOSE: To determine whether low-dose recombinant human parathyroid hormone (rhPTH) would have a beneficial effect on regenerate healing and surrounding bone in a rabbit model of rapid mandibular distraction osteogenesis (DO). MATERIALS AND METHODS: Twenty-eight rabbits underwent unilateral mandibular lengthening at a rapid rate of 2 mm per day for 5 days. From the first day of DO, the experimental group received daily subcutaneous injections of rhPTH 10 mug/kg for 30 days and the control group received the same volume of saline (n = 14 in each group). At 6 weeks after completion of DO, the distracted callus was examined by micro-computed tomography (micro-CT), histology, and the 3-point bending test. Moreover, bone mineral density of the anterior pin region was evaluated by dual-energy x-ray absorptiometry. RESULTS: Under rapid distraction, poor bone healing was observed in the distracted callus from the control group. In contrast, more mature and abundant bone formation was found in the distracted callus from the experimental group by histologic and micro-CT examinations. Quantitatively, the PTH-treated animals had superior parameters in bone volume fraction, trabecular number, and trabecular thickness and mechanical properties compared with controls (P < .05). Bone mineral density of the anterior pin region was greater in the experimental than in the control group (P < .05). CONCLUSION: Low-dose intermittent rhPTH administration not only enhances new bone formation but also can prevent fixator-related osteoporosis of surrounding segments after rapid mandibular DO in rabbits.