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2022, Vol. 26 ›› Issue (14): 2172-2178Parathyroid hormone promotes bone healing in rabbits after free reduction of mandibular condyle fracturesHuang Zhicai, Xie Liuqin, Wang Guangsu, Zhang Guoxing, Tang Zhenglong
Abstract: BACKGROUND: Surgical reduction and internal fixation are used as the main treatments for severe displacement of condylar fracture. If a bone fragment is disintegrated due to the peeling of the external pterygoid muscle, complications such as delayed healing of condylar fracture block may occur after surgery. Therefore, how to promote bone healing after free reduction of condylar fracture is of concern to clinicians in maxillofacial surgery. OBJECTIVE: To study the effect of intermittent administration of parathyroid hormone on bone healing after free reduction of condylar fracture in rabbits. METHODS: Forty-eight New Zealand rabbits were randomly divided into experimental group and control group, 24 rabbits in each group. An experimental model of free reduction and fixation of mandibular condylar fracture was established in rabbits. The experimental group and control group were respectively subcutaneously injected with 20 μg/kg parathyroid hormone and 1 mL of normal saline on the next day after surgery, respectively. The animals were sacrificed 1, 2, 3 and 4 weeks after surgery. Bone samples at the surgical site were taken for bone healing observation. The expression of osteoprotegerin and receptor activator of nuclear factor kappa B ligand (RANKL) in the fracture area was detected by immunohistochemical staining and real-time fluorescence quantitative PCR. RESULTS AND CONCLUSION: There were more osteoblasts and new callus formed faster in the fracture area with a higher density in the experimental group. In the first 4 weeks after surgery, the number of osteoclasts in the experimental group was less than that in the control group (P < 0.05). The mean absorbance value and mRNA expression level of osteoprotegerin were higher in the experimental group than the control group within 4 weeks after surgery. The mean absorbance value and mRNA expression level of RANKL were lower in the experimental group than the control group within 4 weeks after surgery (P < 0.05). All these findings indicate that the application of parathyroid hormone on the second day after free reduction of mandibular condylar fracture could up-regulate osteoprotegerin and inhibit RANKL expression in the fracture area at the early postoperative stage, thereby promoting the formation of new bone in the fracture area. Key words: mandibular bone, condylar fractures, parathyroid hormone, osteoprotegerin, receptor activator of nuclear factor kappa B ligand |