Prat J, Juan J A, Vera P, Hoyos J V, Dejoz R, Peris J L, Sánchez-Lacuesta J, Comín M
Instituto de Biomecánica de Valencia, València Parc Tecnològic, Spain.
J Biomech. 1994 Apr;27(4):469-78. doi: 10.1016/0021-9290(94)90022-1.
The fracture callus contribution to the total rigidity of external fixator-fractured bone element was analysed. This study was achieved from both theoretical and experimental perspectives. The theoretical study was done using the finite element method with a three-dimensional model. In this model, both the callus and the development of its elastic characteristics were considered. A series of 38 New Zealand-California white rabbits with tibial fractures treated with some external fixation system was used in this study. Such devices could reproduce either rigid or elastic features. The frame dynamization can be obtained at different fracture healing stages. Animals were classified into four series: (1) rigid fixators, (2) dynamized fixators two weeks after surgery, (3) three weeks after surgery and (4) four weeks after surgery. Tension tests were performed to evaluate callus strength. Theoretical results showed significant levels of callus load transmission (85.5%) when the callus elastic modulus is 1/100 of the elastic modulus of intact bone in an external fixator with rigid features. Experimental analysis of the callus obtained with different external fixator systems did not show differences among them. This fact implies that the immature callus theoretically modelled (E = 100 N mm-2) appears early in the rabbit fracture model (before two weeks, when first dynamization was made), for this reason no differences were found between the two types of treatment (rigid and dynamized systems). This fact questions the reliability of the dynamization process in external fixation of fractures and it implies accurate investigations in the clinical field.
分析了骨折骨痂对外固定器-骨折骨单元总刚度的贡献。本研究从理论和实验两个角度进行。理论研究采用三维模型的有限元方法。在该模型中，考虑了骨痂及其弹性特性的发展。本研究使用了38只新西兰-加利福尼亚白兔，它们的胫骨骨折采用了某种外固定系统进行治疗。这种装置可以重现刚性或弹性特征。在不同的骨折愈合阶段可以实现框架动力化。动物被分为四个系列：(1)刚性固定器，(2)术后两周动力化固定器，(3)术后三周动力化固定器，(4)术后四周动力化固定器。进行拉伸试验以评估骨痂强度。理论结果表明，在具有刚性特征的外固定器中，当骨痂弹性模量为完整骨弹性模量的1/100时，骨痂载荷传递水平显著(85.5%)。对不同外固定系统获得的骨痂进行的实验分析未显示它们之间存在差异。这一事实意味着，理论建模的未成熟骨痂(E = 100 N/mm²)在兔骨折模型中出现较早(在两周前，即首次进行动力化时)，因此在两种治疗方式(刚性和动力化系统)之间未发现差异。这一事实质疑了骨折外固定中动力化过程的可靠性，这意味着需要在临床领域进行准确的研究。
