| Start Date: | 9/21/2016 | Start Time: | 9:00 AM |
| End Date: | 9/21/2016 | End Time: | 11:00 AM |
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Event Description
BIOMED PhD Thesis Defense
Title:
Contact Mechanics and Mechanical Failure Characterization of Soft Arthroplasty Materials for Knee Cartilage Resurfacing
Speaker:
Mariya Tohfafarosh, PhD Candidate, School of Biomedical Engineering, Science and Health Systems
Advisor:
Steven Kurtz, PhD, Associate Research Professor, School of Biomedical Engineering, Science and Health Systems
Abstract:
Osteoarthritis is the most common cause of disability affecting millions of people worldwide. Total knee replacement is the current state-of-art treatment to alleviate pain and improve mobility among patients in the late stage of knee osteoarthritis. However, total knee replacements are not recommended for younger as well as elderly patients. This work explores the potential of using softer materials such as polycarbonate urethane, Bionate, and a novel hydrogel, Cyborgel, for use in an early intervention knee resurfacing device.
Both of the materials have shown cartilage-like mechanical and lubrication properties, as well as lower wear rates upon testing under physiological loads for several millions of cycles. Additionally, since an important aspect of medical device development is material sterilization, polycarbonate urethane has also been evaluated for the effect of gamma sterilization on its mechanical and chemical integrity. Similarly, this thesis will first evaluated the effect of e-beam and gamma radiation on the hydrogel swell ratio, and the mechanical, chemical and tribological behavior. Using finite element analysis, the hydrogel mechanical behavior was also modelled using a biphasic neo-Hookean material model with less than 2% uncertainty. The results showed no significant difference in the hydrogel swell ratio, mechanical and tribological properties of both sterilization methods, except for the minor changes in the chemical spectra of e-beam sterilized samples.
Polycarbonate urethane and the hydrogel were then investigated for the contact mechanics of soft-on-soft knee implant configuration using a finite element analysis approach. A simplified, axisymmetric, medial knee model was developed and validated, and a parametric analysis was carried out to evaluate the effect of conformity, implant thickness and material properties on the contact mechanics of a soft material knee resurfacing implant. The resulting contact mechanics were most sensitive to the changes in conformity, followed by material properties and implant thickness. Based on the results of this study, a femoral-tibial conformity of ≥ 95% and material strength greater than 10MPa was recommended for the design of soft arthroplasty material implant with as low as 2mm implant thickness. Finally, a battery of mechanical tests were carried out in order to evaluate the failure criteria of the two proposed materials under uniaxial tension, unconfined compression and plane strain compression at physiologically relevant strain rates. These results provided important information about the material behavior as well as insights on the failure mode that are critical while designing a knee cartilage replacement implant.
Overall, the potential of two soft materials, for use in knee resurfacing implant, was thoroughly examined and confirmed in this thesis, and the results provided base work for future testing and development of the implant. Such implant would be a promising treatment to prolong total knee replacement, especially among younger and elderly patients. |
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Location:
Bossone Research Center, Room 709, located at 32nd and Market Streets. |
Audience:
Undergraduate StudentsGraduate StudentsFacultyStaff |
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