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How to measure tension in tissues in-vivo

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  • How to measure tension in tissues in-vivo

    Dear Biomech-L list members
    I am working on modeling the knee as my PhD project and I'm wondering if there are any in vivo information about the amount of tension in tissues around the knee, i.e. ligaments, menisci, and fascia. I would be grateful if you can provide me with some references. Also I would be grateful if you could advise me how we can do in-vivo experiments to find out the tissue tensions. I have already found this paper in which it has been suggested that we can use MRI machine to measure tissue stiffness. But how can we measure the tension?
    Jenkyn, T. R., R. L. Ehman, et al. (2003). "Noninvasive Muscle Tension Measurement Using the Novel Technique of Magnetic Resonance Elastography (MRE)." Journal of Biomechanics 36: 1917–1921.
    A novel method for direct measurement of the state of skeletal muscle contraction is introduced called magnetic resonance elastography (MRE). Such a technique is useful for avoiding the indeterminacy inherent in most inverse dynamic models of the musculoskeletal system. Within a standard MRI scanner, mechanical vibration is applied to muscle via the skin, creating shear waves that penetrate the tissue and propagate along muscle fibers. A gradient echo sequence is used with cyclic motion-encoding to image the propagating shear waves using phase contrast. Individual muscles of interest are identified and the shear wavelength in each is measured. Shear wavelength increases with increasing tissue stiffness and increasing tissue tension.
    Several ankle muscles were tested simultaneously in normal subjects. Applied ankle moment was isometrically resisted at several different foot positions. Shear wavelengths in relaxed muscle in neutral foot position was 2.34±0.47 cm for tibialis anterior (TA) and 3.13±0.24 cm for lateral gastrocnemius (LG). Wavelength increased in relaxed muscle when stretched (to 3.80±0.28 cm for TA in 45° plantar-flexion and to 3.95±0.43 cm for LG in 20° dorsi-flexion). Wavelength increased more significantly with contraction (to 7.71±0.97 cm in TA for 16Nm dorsi-flexion effort and to 7.90±0.34 cm in LG for 48Nm plantar-flexion effort).
    MRE has been shown to be sensitive to both passive and active tension within skeletal muscle making it a promising, noninvasive tool for biomechanical analysis. Since it is based on MRI technology, any muscle, however deep, can be interrogated using equipment commonly available in most health care facilities.
    Feras Hakkak
    PhD student
    Biomed. Engg. Dept.
    AmiKabir Univ. of Tech.
    Tehran, Iran