Influence Of Periosteum On Local Morphology And Histology After Outer Cortex Osteotomy Of Mandibular Body:an Experimental Study In Young Miniature Pigs

Background:Mandibular outer cortex osteotomy is an emerging clinical technique. Is it feasible to perform mandibular outer cortex osteotomy in children? Will the removal of the mandibular outer cortex in children affect the normal growth of the mandible? Very few animal studies and clinical experiments have addressed these issues. In the previous study, we used young miniature pigs as experimental animals. Unfortunately, some animals (37.5%) exhibited mandible deviation after outer cortex osteotomy of mandibular body. The aim of this study was to evaluate the role of periosteum on the healing and growth of mandible after the operation and the relation of periosteum and mandible deviation.Methods:This experimental study included two parts. In the first part, three-month-old miniature pigs were used as experimental animals and were randomised into four groups. Experiment A:The osteotomy was performed on both sides. At the same time, the periosteum around mandibular body was excised on the left side. Experiment B:The osteotomy was performed on the left side with periosteum excised. Experiment C: Subperiosteal stripping was performed on the right side. Experiment D:Blank control. The morphology of skull and mandible was analysed using3D-CT technique before and after surgery to evaluate the relation of periosteum and mandible deviation. In the second part, the experimental animals were randomised into two groups. Experiment A:The osteotomy was performed on both sides. At the same time, the periosteum around mandibular body was excised on the left side. Experiment B:The osteotomy was performed on the left side with periosteum excised. The histologic analysis of HE stain, immunohistochemical staining and electronic microscope scanning was evaluated at4,12and24weeks after surgery. From the view of bone formation/bone resorption, apoptosis and osteoimmunology, the role of periosteum on the healing and growth of mandible and the relation of periosteum and mandible deviation were evaluated.Results:In the first part, some animals (66.7%) exhibited obvious mandible deviation after surgery in experiment A, which occurred on3-6months after surgery. In experiment B and D, no mandible deviation was observed. All the animals exhibited slinghtly mandible deviation after surgery in experiment A, which occurred at3months after surgery. The influence of periosteum on the development of mandible after surgery occurred in the body of mandible. In the second part, we found the bone wound healed well on the side with periosteum while poor without periosteum. The osteogenesis mode was intramembranous ossification on the side with periosteum and endochondral ossification without periosteum. During the bone wound healing and bone remodeling, the expression of bone morphogenetic protein-4, osteoprotegerin, receptor activator for nuclear factor kappa B ligand, caspase-3and so on was different from normal. The balance between bone formation and bone resorption was unable to maintain after surgery and the imbalance interfered with normal bone growth, especially on the side without periosteum.Conclusion:Firstly, periosteum played an important role on the bone wound healing and bone remodeling. Secondly, mandibular outer cortex osteotomy would inhibit the development of mandible. The periosteum was one of the major factors causing post-operative mandible deviation.