颞下颌关节继发性强直与幼年期髁状突纵行骨折的关系

背景髁状突骨折作为一种较严重的颞下颌关节(temporomandibular joint,TMJ)损伤受到学者们关注.但是,受诊断方法限制,学者们一直对髁状突横断骨折研究较多,而对髁状突纵行骨折研究较少,对儿童髁状突纵行骨折了解更少.目的探讨幼年期髁状突纵行骨折对TMJ继发性强直的影响.设计随机对照的实验研究.单位解放军总医院口腔科.材料实验在解放军总医院实验动物中心完成.选择北京农业大学实验动物研究所培育的中国实验用小型猪12头,两三个月龄,体质量5～5.5kg,混合饲料喂养,随机分为3组.方法小型猪于术前12 h禁食水,以5.0～15.0 mg/kg噻胺酮腹腔麻醉.麻醉成功后取右侧卧位,常规消毒,左耳前切口,横行切开关节囊,暴露髁状突,牵拉髁状突向下,用宽5 mm小骨凿沿内侧1/3处纵行劈骨,造成前后矢状骨折.于术后3个月与6个月分批处死动物,取其髁状突标本进行观察.主要观察指标①肉眼观察3组动物髁状突标本的形态学变化.②光镜观察3组动物髁状突标本的组织学改变.结果术后3个月组可见关节盘与髁状突明显粘连(下称盘突粘连),其中1例可见关节窝、关节盘、髁状突之间均出现粘连,2只动物形成双髁状突畸形,未见关节盘穿孔.术后6个月组见盘突粘连紧密,3只动物形成双髁状突畸形,关节盘则明显增厚.光镜检查骨折后3个月见盘突粘连明显,粘连部位与周围组织的界限不清,粘连区由纤维结缔组织组成,内含大量的软骨细胞,部分粘连区纤维结缔组织与骨小梁紧密结合,关节盘纤维排列紊乱,出现血管及脂肪细胞.骨折后6个月粘连组织内可见血管、大量的成纤维细胞及散在的软骨细胞.关节盘胶原纤维排列呈旋窝状内含大量脂肪细胞并可见血管.在未粘连部位可见髁状突表面纤维软骨增厚,表面纤维排列紊乱.关节盘表面呈增生改变.结论幼年期髁突纵行骨折对TMJ造成严重继发性损伤,髁突纵行骨折与关节强直关系密切.

Relationship between secondary ankylosis of temporomandibular joint and childhood longitudinal fracture of mandibular condyle

BACKGROUND: Much attention has been focused on mandibular condyle fracture, which has long been considered as a severe injury to the temporomandibular joint(TMJ). Restricted by diagnostic methods, many studies have been conducted on transverse fracture whereas little attention has been paid to longitudinal fracture of the mandibular condyle. Even less is known about longitudinal fracture in young children.OBJECTIVE: To evaluate the effects of childhood longitudinal fracture of the mandibular condyle on secondary ankylosis of TMJ.DESIGN: A randomized controlled study.SETTING: Department of Stomatology, General Hospital of Chinese PLA.MATERIALS: The experiment was completed in the Center for Experimental Animals, General Hospital of Chinese PLA. Twelve young Chinese experimental miniature pigs bred by the Institute of Experimental Animals, Beijing Agriculture University, aged 2 -3 months and weighing(5 -5.5) kg, were used and raised with mixed feed, and then divided into 3 groups randomly.METHODS: Food and water was forbidden for the miniature pigs 12 hours before operation. Under anesthesia with(5.0 - 15.0) mg/kg ketamine/xylazine abdominally injected, conventional disinfection was performed in the right lateral decubitus position and layer-by-layer preauricular incisions were made on the left side of the miniature pigs. The joint cyst was incised transversely and the lower cavity of TMJ was exposed and dragged downwards. The mandibular condyle was cleaved into two vertically along the inner 1/3 part of it with a 5.0 mm-wide bone chisel to cause inferior and posterior sagittal fractures. The miniature pigs were executed 3 months and 6 months after operation, and their condyles were cut for observation.MAIN OUTCOME MEASURES:①The morphological changes of mandibular condyle specimens in the three groups observed with the naked eyes.②The pathological changes of mandibular condyle specimens under light microscope.RESULTS: The articular disc was adhered to the mandibular condyle after 3months. Temporal fossa adhered to the articular disc and mandibular condyle could still be observed in one specimen. Bifid condylar deformity was found in two specimens and no disc perforation was found. The adhesions became more severe after 6 months and bifid condylar deformity was formed in all the 3 specimens, with distinctly thickened discs. Light microscope observation:Three months after fracture, the adhesion between disc and condyle was obvious. There was no clear boundary between the surrounding tissues. The adhesion was composed of fibro-connective tissues, with a large number of chondrocytes in it. Fibro-connective tissues tightly adhered to the trabeculae were found in some adhesions. The fiber of disc became deranged and blood vessels and fatty cells were seen. Six months after fracture, blood vessels, a large number of fibroblasts and sparse chondrocytes were seen in the adhesions. The collagen fibers of the discs were arranged in whirlpool shape. There were a large number of fatty cells and blood vessels within it. The fiber-cartilage of the condylar surface was found thickened and the fiber deranged in the unadhered tissues. Proliferative changes were seen on disc surfaces.CONCLUSION: Childhood longitudinal fracture of the mandibular condyle causes severe secondary injury to TMJ, suggesting a close correlation between longitudinal fracture of the mandibular condyle and TMJ ankylosis.