OPTIMIZATION FIXATOR STIFFNESS DURING FRACTURE HEALING

骨折愈合期间优化固定器刚度

• 批准号: 2081296
• 负责人: ALFRED F BEHRENS
• 金额: $ 17.66万
• 依托单位: UNIV OF MED/DENT OF NJ-NJ MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-15 至 1995-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2081296
• 关键词: biological models; bone regeneration; dogs; fracture fixation; human subject; human therapy evaluation; immobilization of body part; limb fracture; nonhuman therapy evaluation

The cost of treating complications of severe open and closed long bone fractures amounts to more than a billion dollars a year. Many of these fractures are managed with external fixators which permit optimal care of associated soft tissue injuries, but provide mechanical conditions neither ideal for primary nor secondary bone healing. It is the long- term goal of this proposal to decrease healing times and healing failures in complex fractures by optimizing the mechanical properties of external fixators. While it is accepted that fixator rigidity and fracture consolidation are related, clinical and experimental attempts to determine optimal fixator rigidities have led to equivocal results. It is our hypothesis that: 1) fixator rigidities substantially lower than the bending stiffness of the corresponding long bone will result in a more rapid increase in callus stiffness, faster callus proliferation and shorter healing times than the use of stiffer external fixators, and that (2) optimal fixator rigidity in the early part of fracture healing is different from optimal rigidity in the latter part of the healing process. To test these hypotheses and further develop our assessment methods, we have designed four studies: (1) We shall immobilize the tibia in a canine fracture model with 4 fixators of widely varying stiffness. The healing process is assessed weekly by recording changes in callus volume radiographically and changes in callus stiffness with a 6-degrees-of-freedom instrumented external fixator in conjunction with a finite element model (FEA) of the fixator-bone construct. The resulting curves of changing callus dimensions reflect the intensity of callus proliferation and the curves of changing callus stiffness allow us to determine the time relationship of fixator stiffness to callus consolidation. (2) Based on the findings of the initial study, we shall determine the in vivo healing curves in two fixator regimens that exchange low fixator stiffness in the early part of the healing course with high fixator stiffness later and vice versa. (3) With the help of the same technology, we shall determine in vivo healing curves in humans with severe tibial fractures and develop a protocol to optimize fixator stiffness in humans. (4) We shall enhance the performance of the FEA model by incorporating nonlinear behavior and further develop it to gain insight into problems at the pin-bone interface and the mechanics of complex fractures. We believe that the combination of a carefully controlled animal model, the ability to make repeated, sensitive in vivo measurements of callus volume and callus stiffness, and the use of a finite element model that represents the whole fixator-bone construct, will allow us to clarify the long-standing, but clinically important issue of optimal fixator stiffness for the treatment of severe fractures. Later we shall adapt the same technology to explore how other mechanical, metabolic or pharmacological modalities can further accelerate the fracture healing process.

严重长骨开放与闭合并发症的治疗费用 骨折造成的损失每年超过十亿美元。 许多这些 骨折用外固定器治疗， 相关的软组织损伤，但提供机械条件 对于原发性或继发性骨愈合都不理想。 它是漫长的- 这项建议的长期目标是减少愈合时间和愈合 通过优化复合材料的力学性能， 外固定器 虽然公认固定器刚度和骨折巩固 是相关的，临床和实验的尝试，以确定最佳的 固定器的刚性导致了不确定的结果。 我们假设 1）固定器刚度显著低于弯曲 相应长骨的刚度将导致更快速的 愈伤组织硬度增加，愈伤组织增殖更快， 愈合时间比使用更硬的外固定器要长，并且（2） 骨折愈合早期最佳固定器刚度为 与愈合后期的最佳刚度不同 过程 为了验证这些假设并进一步发展我们的评估方法，我们 设计了四项研究： (1)我们将胫骨固定在犬齿骨折模型中， 刚度变化很大的固定器。 评估愈合过程 每周通过放射学记录骨痂体积的变化， 骨痂硬度的变化与6自由度内固定 外固定器结合有限元模型（FEA）， 固定器-骨结构。 由此产生的变化愈伤组织的曲线 维数反映了愈伤组织增殖的强度， 改变骨痂硬度使我们能够确定时间关系 外固定支架硬度与骨痂巩固的关系。 (2)根据初步研究的结果，我们将确定 两种更换下固定器的固定器方案中的体内愈合曲线 高位外固定器愈合早期僵硬 硬度较低，反之亦然。 (3)在相同技术的帮助下，我们将在体内确定 严重胫骨骨折患者的愈合曲线， 优化人体内固定器刚度的方案。 (4)我们将通过结合 非线性行为，并进一步发展它，以深入了解问题 以及复杂骨折的力学机制。 我们相信，结合精心控制的动物模型， 对愈伤组织进行重复、灵敏的体内测量的能力 体积和骨痂刚度，并使用有限元模型， 代表了整个固定器-骨结构，将使我们能够澄清 长期存在的，但临床上重要的问题，最佳固定器， 用于治疗严重骨折的硬度。 稍后我们将适应 同样的技术来探索其他机械、代谢或 药理学方法可以进一步加速骨折愈合 过程