Date of Award

7-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

Benson, Lisa

Committee Member

LaBerge , Martine

Committee Member

Bateman , Ted

Abstract

Biomechanical evaluations of fracture fixation devices attempt to determine implant performance by approximating the in vivo conditions. This performance is affected by many factors and relies on the complex bone-implant interface. Biomechanical tests can be designed in a variety of ways in order to evaluate device performance with respect to any number of these bone-implant interactions. Standardized tests, designed by groups such as the American Society for Testing and Materials (ASTM), are often designed either to determine the performance of a specific type of fixation device or for direct comparison between different devices. Additionally, many biomechanical evaluations are designed for direct comparison between the devices being evaluated. Often times these tests utilize bone analogs in order to eliminate variability. Finally, the method and location of load application greatly influences device performance outcomes. Cyclic tests determine fatigue performance whereas quasi-static tests are used to define device limits (i.e. - Young's modulus, and ultimate/yield properties). Physiologically equivalent loading patterns expose fixation devices to combined loading modalities most closely resembling the in vivo conditions.
This paper will explore the variety of ways in which biomechanical testing of fracture fixation devices are performed. Specific focus will be given to the design and application of biomechanical tests which simulate physiologically relevant loading. Physiologically relevant/equivalent loading refers to the simulation of in vivo loads with respect to anatomic alignment. This examination will include details regarding the differences in biomechanical test designs between weight-bearing (i.e. - lower limb) and non-weight-bearing (i.e. - upper limb) fixation devices. These concepts will then be put to use for the purpose of evaluating the biomechanical performance of two methods of humeral shaft fixation. The results of this study have been submitted for publication in the Journal of Surgical Orthopaedic Advances.

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