The Effects of Freezing on the Properties of Bovine Meniscus

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The Effects of Freezing on the Properties of
Bovine Meniscus

• Scott Morgan

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What Is Meniscus?

• Semi-lunar fibrocartilage
• Lateral
• Medial

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Importance?

• Provide smooth, low friction articulating
  surfaces
• Serve as shock absorbers and stabilizers
• When injured and/or removed
• Degeneration leading to osteoarthritis
• Knee movement becomes more difficult

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Why freezing?

• Literature review (Proctor et al, J of Ortho R,
  1989)
• Experimental menisci described as fresh
• Frozen to microtome twice during slicing
• Menisci are roughly 70 water
• No studies to determine effect of freezing on
  material properties

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Materials Methods
Lateral
Medial

• Bovine menisci
• Obtained from local slaughterhouse
• Medial meniscus only ? to reduce variability

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Methods

• Treatment Groups ?5
• Control (Fresh)
• 4 Freeze/Thaw Cycle (FTC) Group
• 1 FTC 5 days frozen, 2 days thawed
• 2 FTC
• 3 FTC
• 4 FTC

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Methods
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Methods

• 12 Menisci per treatment
• Minimum of 5 slices
• Maximum of 15 slices
• Thickness measured
• Dial caliper
• Sandpaper glued to ends
• Facilitated gripping in fixture
• Provided gage length

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Methods

• MTS servohydraulic mechanical testing system
• Computerized data acquisition
• Custom gripping jig
• Performed tensile test

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Methods

• Tensile test
• 1 N preload
• Photograph for later digital analysis for
  specimen dimensions
• 0.5 mm/min crosshead speed
• Tensile tested until failure

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Methods

• Data analysis
• Digital image analysis
• Specimen dimensions from photos
• Calculate stress strain
• Plot stress-strain curve

(Wainwright, 1976)
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Statistical Analysis

• Compared menisci within each treatment
• Look for individual variability
• Compared treatment groups
• ANOVA
• Multiple comparisons Tukey-Kramer

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Conclusions

• Large variability between specimens
• Increasing FTCs lead to increasing variabilitity
• There appears to be little to no effect of
  multiple FTCs on the tensile strength of the
  circumferential collagen fibers

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Current

• Changes in the specimens
• Texture
• Ease of slicing
• Creep Relaxation Testing
• Design of new apparatus
• Compression indenter
• New experimental procedure
• Meniscus from other species
• Ovine
• Porcine

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Acknowledgments

• Dr. Carolyn Skurla
• Daniel Bland
• Zachary Kelm
• Erik Schaefer
• Christopher Towe
• David Webster