三维有限元法分析横形斜形骨折对骨折愈合的影响

目的采用三维有限元法比较横形骨折、斜形骨折在同一部位、相同条件下骨折愈合的速度,为临床判断骨折愈合解除外固定时间提供理论依据。方法以三维有限元法分析肱骨中段横形、斜形骨折在骨痂同样充满断端且骨痂力学性能相同条件下,分别在肢体远端纵轴、水平轴和矢状轴方向上施加相同载荷,比较两种骨折断端间的最大应力值和最大位移量,及肢体远端的最大位移量。结果在肢体远端各种加载条件下横形骨折的断端在同一平面上受力和位移相差不多,要使之破坏加载力必须达到较高的值。而斜形骨折因骨折断端不在同一平面上,所受应力和位移相差较大,近端受力大、位移小,远端受力小、位移大,要使之破坏只要较小的加载力,骨折近端即可首先出现断裂,继之因应力集中而波及整条骨折线,使骨骼再次骨折。纵轴加压或拉伸对肢体远端的位移影响少,而水平轴和矢状轴方向尽管加载力较小,仍能产生肢体远端的较大位移。结论在相同部位、相同力学条件下,横形骨折比斜形骨折愈合快。

Analysis of the affects by transverse or oblique fractures on the bone healing with 3-D limited elementary method

Objective To provide theoretical basic for clinical judge of bone healing and to determine the removing time of the outer fixator by comparing the healing speed of transverse fracture with that of oblique fracture in the same locality under the same condition. Method Using three-dimensional limited elementary analytic method to analyze the maximum stress values, the maximum shifting quantity and the maximum quantity between the two far endings of extremities in the middle of the skeleton under the same condition as the callus with the same mechanical function filling up the both endings when placing the same loads on the perpendicular axis, transverse axis and the sagittal axis, and to compare the differences between the two kinds of fractures-transverse fracture and oblique fracture. Result At the far ends of the extremities under various kinds of loans, the stress and shifting shows little difference in the same surface for the transverse fracture. To make it broken, the loads need to reach fairly high value. For the oblique fracture, the stress and shifting appeared on them are rather distinctive because the two endings of the fracture were not in the same surface. The near end received more power and appeared less shifting while the far end received less power but larger shifting. Only bythe less loads could make it broken .The near end would become broken first, and affected the whole fracture line because of the dense of stress, then caused afresh fracture. Pressure or extension placed upon the perpendicular axis induced less shifting on the far end of the extremities while pressure placed upon the horizontal axis and the sagittal axis could cause larger shifting even though with the less pressure. Conclusion In the same locality and under the same condition of mechanical function, the transverse fracture could be concrescence faster than that of the oblique fracture.