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首页> 中文期刊> 《中国组织工程研究》 >儿童肱骨髁上骨折残留移位复位模型：力学响应的有限元分析

儿童肱骨髁上骨折残留移位复位模型：力学响应的有限元分析

         
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背景：远端骨折块的移位是造成儿童肱骨髁上骨折治疗后肘内翻畸形发生的原因之一，临症治疗时多强调纠正后尺侧偏移，复位经验是否具有力学上的优势，缺乏现有的实验依据。目的：建立伸直尺偏型肱骨髁上骨折有限元模型，探讨骨折整复后存在功能复位标准范围内残留移位情况下骨折端的力学响应情况，以此为“宁前勿后，宁桡勿尺”的复位经验法则提供力学证据。方法：选择新鲜7岁儿童右上肢尸体骨一副进行CT 扫描，建立残留移位骨折复位有限元模型，再根据骨折块移位的方向和接触面积的大小分组进行外力加载，记录骨折端面前后缘应力值及Baumann角，分析对比数据。结果与结论：后内侧移位下后侧缘应力值显著增高，后侧移位组次之，接触面积为75%时应力值显著高于其他组；前侧缘应力值对比中，前内侧移位与其他组应力值差异有显著性意义，85%接触面积下应力值普遍较高；前后侧缘应力对比示后侧移位时应力增幅明显高于前侧移位，内侧移位时载荷后Baumann角显著增高。提示移位方向改变应力集中的区域，相比较而言，后方移位下应力增量更加显著，骨折端接触面积减少，相应统计区域的应力明显升高，远端骨折块正内侧移位显著改变Baumann角，实验结果在力学上支持肱骨髁上骨折远端骨折块移位的假说，“宁前勿后，宁桡勿尺”的复位经验原则有一定力学上的依据。%BACKGROUND:Displacement of the distal fracture fragment is one of the most important facts that lead to cubitus varus fol owing pediatric supracondylar humeral fracture. Mainstream technique emphasized the restoration of posterior-ulnar deviation of the distal fragment. However, there is an absence of supportive evidences from biomechanical studies. OBJECTIVE:To establish models of extension-ulnar type of supracondylar humeral fracture and investigate the mechanical stability of reduced fracture with residual displacements within functional restoration standard, so as to provide mechanic evidences supporting the empirical rule of manipulative reduction-“better anterior than posterior, better radial than ulnar”. METHODS:The fresh cadaveric bone of right upper extremity from a 7-year-old child was scanned using CT. Models of supracondylar humeral fracture differing in contact area of the fracture site and displacement direction of the distal fragment were established and underwent loading tests. Stress in both anterior and posterior margin of the fracture site and Baumann angle were recorded, and data were analyzed and compared. RESULTS AND CONCLUSION:In comparison of stress in the posterior margin, the value was significantly greater in the posteromedial-displacement group than the others. Stress value in fracture with 75%contact area was significantly greater than the other three groups. In comparison of stress in the anterior margin, a significantly greater value was obtained in the posteromedial-displaced group. Stress value in fracture with 85%contact area was significantly greater. When comparing stress in posterior margin and anterior margin, the absolute increment of stress value was greater in posterior displacement group than in anterior displacement group. Baumann angle increased significantly when fragment displaced medial y. Above findings indicated that displacement direction altered the location of stress concentration. Stress augmentation was greater in posterior displacement group. Stress in related area significantly increased constantly when contact area of the fracture site reduced. Baumann changed obviously when fragment displaced medial y. The results preliminarily verify the hypothesis that displacement of the distal fragment was the main contributor to cubitus varus fol owing supracondylar humeral fracture. These findings provided certain evidences supporting the empirical rule“better anterior than posterior, better radial and ulnar”.

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