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What determines whether an avulsion fracture or a ligament rupture will occur?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Oct 2, 2014.

  1. markjohconley

    markjohconley Well-Known Member

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    If you pull out a weed slowly you get the roots, if quickly it will most likely snap off along the stem; however this analogy doesn't hold for ligaments, the quicker the stress is applied the more likely the avulsion fracture, yes/no?
  2. markjohconley

    markjohconley Well-Known Member

    Anyone, bump
  3. Lab Guy

    Lab Guy Well-Known Member

    The analogy does not hold up as weeds do not exhibit viscoelastic properties.

    If the stress is high and applied quickly, then it's less likely an avulsion fracture will occur. Instead, the collagen fibrils of the ligament will quickly become very stiff, not elongate and go to ultimate failure resulting in a severe sprain or rupture.

    If the stress slowly and steadily increases, the collagen fibrils will elongate but before the ligament goes to ultimate failure, the bone, with it's higher stiffness/elastic Modulus will fail first resulting in an avulsion fracture.

    It is also more likely that tearing of the ligament will happen when stress is applied quickly or slowly in patients with thin ligaments, or had previous injuries as the visco elastic characteristics have been compromised.

    Let me know if I am off track.

  4. Depends of what is the weakest, and the relative force , and where the force is coming from ie lever arm type of idea.

    whatever goes 1st will generally protect the others from going, not always ofc.

    a classic example of this is Bo Jackson


    Muscles were so strong supporting the hip joint , the wrong things got damaged ended a career in the NFL and andshortened one iin baseball
  5. markjohconley

    markjohconley Well-Known Member

    hip dislocation > avascular necrosis (had to google that one)
  6. Yep, but at the time Dr were saying Bo Jackson leg should nhave broken, but the muscles supporting the pelvic region and femur were so strong, the femur did not break, but something had to give
  7. efuller

    efuller MVP

    I agree. If you pull on a chain, the weakest link will break. Although my wife keeps on putting up a hanging basket in the kitchen and filling it with onions. It keeps breaking at the top link. The link at the top is the one that keeps breaking. The top link has to hold the additional weight of all the links below it. The links are pretty small, so I'm just going to go with the top one being the weakest.

    Then there is perforated toilet paper.....


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