Biomechanics of 6-pin unilateral external skeletal fixation devices /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1992.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | External skeletal fixation devices are commonly used in human and veterinary orthopedics. Although they have proven their effectiveness over the years, they still are associated with many complications including premature pin loosening, implant breakage, and pin tract infection. A more thorough understanding of the biomechanics of external fixation is needed before patient morbidity can be minimized. This study utilizes different analytical and experimental techniques to predict the performance of a 6-pin unilateral external fixator in terms of deflection, load carrying capacity, and loads transferred to the pins and bone at the pin/bone interface for an axial load on the bone, which is the primary load experienced by a fixator in this application. The four techniques utilized were analytical analysis, finite element analysis (FEA), and in vitro and in vivo experimentation. FEA proved to be a very versatile and accurate tool with an accuracy of 97.5% when compared to the analytical analysis of simplified cases. Furthermore, unlike the analytical analysis. FEA allowed modeling the bar and the bone as non-rigid members. One surprising result, observed in both the FEA and in vitro experiments, was that in each side of a 6-pin unilateral fixator under a purely axial load, the middle pin experienced tension and the outer pins compression. Additionally, increasing the stiffness of the external bar decreased the axial loads, and more evenly distribute the end shear loads and end moments in the pins. The axial loads on the pins that were determined in this study were, for the most part, below the values that have been documented in the literature for pullout resistance of pins. However, for non-threaded pins, the axial loads found would come very close to and sometimes surpass pullout resistance. With respect to local failure of the surrounding bone, the ultimate compressive strength of bone could be reached if care is not taken in regards to proper pin insertion, maintaining allowable loads, and pin insertion in sufficiently large and homogeneous bone. However, this does not guarantee that the pins will not loosen since other considerations must be taken into account including local stress concentrations. The key to a successful fixator remains proper design selection, pin insertion, and maintenance after surgery. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Bioengineering." |
| Physical Description: | xi, 132 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |