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Date of Final Oral Examination (Defense)
Type of Culminating Activity
Thesis - Boise State University Access Only
Master of Science in Mechanical Engineering
Mechanical and Biomechanical Engineering
Trevor Lujan, Ph.D
Clare K. Fitzpatrick, Ph.D
Cheryl Jorcyk, Ph.D
Mahmood Mamivand, Ph.D
The meniscus is a soft fibrous tissue that distributes cyclic loads across the knee joint. It is frequently injured, and one likely mechanism for failure is repeated exposure to low-magnitude loads, known as high-cycle fatigue. When a tear occurs, it causes a disruption of function, leading to swelling and pain, as well as an increase in the likelihood of development of osteoarthritis by six-fold. Though meniscus tears due to fatigue are clinically relevant, the fatigue properties of meniscus are poorly understood. In fact, current literature only describes fatigue properties of bovine meniscus up to 20,000 cycles at stress levels much higher than daily loading activities. This research aims to fill the gap in knowledge regarding high-cycle fatigue properties of human meniscus through three steps: 1) develop a test procedure that reduces the incidence of invalid clampsite failures, 2) perform quasi-static tests to correlate the ultimate tensile strength (UTS) of human meniscus to linear modulus, and 3) perform tension-tension fatigue testing at 20%, 35% and 55% of the predicted UTS until failure or a maximum of one million cycles is reached.
A test procedure was successfully developed that eliminated clamp site failures in 95% of meniscus tensile tests. This test procedure used specimen geometry based on ASTM test standards and used innovative cutting techniques to improve the tolerance of specimen width and thickness. The quasi-static tensile testing of meniscus from donors under 40 years old resulted in a good correlation between linear modulus and UTS (R2 = 0.75). Also, regional variability in material properties was present when comparing the anterior medial meniscus (UTS = 24.5 ± 2.6 MPa) to the posterior medial meniscus (UTS = 7.9 ± 4.9 MPa). Fatigue tests of human meniscus under 40 years old resulted in an average creep rate of 0.02% per 1000 cycles, and an average total creep of 2.4 mm for specimens that failed in fatigue. Results from the S-N curve indicated a strong log-linear correlation for fatigue life (R2=0.99). Interestingly, specimens tested at 20% UTS and one specimen tested at 35% UTS reached the maximum one million cycles without failing. For below 30% UTS, median fatigue failure was estimated to occur after 30 million cycles. This suggests that meniscus may have an effective endurance limit below 30% UTS. The creation of the S-N curve allows for cycles to failure estimations to be made based on applied stress during cyclic activities such as walking or running. Future work includes performing fatigue tests on human meniscus over 65 years old to determine the effect of age-related changes in the extracellular matrix on fatigue life.
Krentz, Madison Elizabeth, "High-Cycle Fatigue Life of Human Meniscus" (2018). Boise State University Theses and Dissertations. 1483.