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Improved Healing of Large, Osseous, Segmental Defects by Reverse Dynamization: Evaluation in a Sheep Model

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Technical Report,30 Sep 2013,29 Sep 2017

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Mayo Clinic Mayo Clinic United States

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This project was designed to determine whether reverse dynamization promoted the healing of critical size defects in sheep, as demonstrated in our earlier rat studies. It had two components. In Specific Aim 1,a novel external fixator was designed and subjected to rigorous testing to establish its mechanical properties and suitability for reverse dynamization. This was supplemented by finite element analysis and the use of a strain gauge. This aim was successfully completed, with the external fixator providing 293 Nmm stiffness in the low stiffness position, and 562 Nmm in the high stiffness position. In Specific Aim 2 it was intended to use a 3 cm tibial defect model to compare healing under conditions of high and low stiffness, dynamization and reverse dynamization. However, persistent hardware failuresrequired the sheep to be euthanized. This occurred whether or not the sheep were supported by a sling. Strain gauge data suggested that the peak cycle forces across the defect normally remained below 500N which, according to our mechanical testing data, was well within the capability of the fixator to support. However, CCTV data and strain gauge data suggest that the sheep would sporadically kick, and this led to catastrophic failure of the metal-ware.

Subject Categories:

  • Medicine and Medical Research
  • Anatomy and Physiology
  • Mechanics

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