下颌骨骨折载荷和骨折移位方式的关系探讨

The relationship between different loads and displacement in mandibular fractures

目的:通过对单侧下颌骨移位骨折的临床分析,探讨下颌骨骨折的模式和生物力学原理。方法:回顾下颌骨单线骨折病例131例,其中男75例,女56例。就其移位方向和骨折部位进行分析。定义骨折线前部为前段骨折,骨折线后端为后段骨折;移位方向定义为舌侧移位、颊侧移位、向上移位、向下移位、轴向挤压、轴向拉伸。所有的骨折移位评价以骨折前段和下颌牙槽嵴为参照。采用SPSS13.0统计软件包对数据进行χ2检验。结果:131例下颌骨骨折病例中,下颌角骨折35例,下颌体骨折32例,颏孔区骨折23例,颏部骨折41例。其中颊、舌向移位90处,上、下向移位75处,挤压、拉伸42处。经确切概率法统计分析,KW=39.606,P=0.001<0.05。下颌骨骨折中,下颌骨承力的方式主要有3种,即弯曲载荷、剪切载荷和扭转载荷,分别作用于3个不同方向。弯曲载荷造成骨折断端的挤压和拉伸,剪切载荷造成下颌骨骨折断端的上、下方向移位,扭转载荷造成骨折断端的颊、舌向移位。结论:在下颌角和下颌体,剪切载荷的骨折效应明显,而在颏部和颏孔区,扭转载荷骨折效应明显。

PURPOSE： This study is aimed to investigate the displacement model of the mandible fracture and the biomechanieal principles based on an analysis of single fractures in 131 mandibles. METHODS： 131 cases with single mandibular fracture were included in the study, including 75 males, 56 females. The anterior and posterior fragments and 6 directions of displacement were defined. The anterior fragment and the superior margin of the mandible were defined as the frame of the reference to evaluate the displacement of the fractured fragment. SPSS 13.0 software package was used for Chi-square test. RESULTS： The fracture of the mandible resulted from three kinds of forces, i.e. bend, torsion and shear moment. The directions of these forces were different and resulted in various displacements, including compressiontension, lingual-buccal and caudal-cranial displacement. The fractures were located at the angle, body, mental foramen and symphysis, accounting for 35, 32, 23, 41, respectively. Lingual-buccal displacement occurred in 90, eaudal-eranial in 75 cases, and compression-tension in 42 cases. The value of KW by Chi-square test was 39.606, P=0.001 〈0.05. CONCLUSIONS： The effect of shear force was distinct at the angle and body fractures, while the effect of torsion moment was most apparent at the symphysis and mental foramen fractures. Supported by Shanghai Leading Academic Discipline Project （Grant No.Y0203）.