Advanced biomechanics of physical activity kin 831 l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 64

Advanced Biomechanics of Physical Activity (KIN 831) PowerPoint PPT Presentation


  • 334 Views
  • Uploaded on
  • Presentation posted in: General

Advanced Biomechanics of Physical Activity (KIN 831). Lecture 2 Biomechanics of Tendons and Ligaments * Material included in this presentation is derived primarily from two sources:

Download Presentation

Advanced Biomechanics of Physical Activity (KIN 831)

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Advanced biomechanics of physical activity kin 831 l.jpg

Advanced Biomechanics of Physical Activity (KIN 831)

Lecture 2

Biomechanics of Tendons and Ligaments

*Material included in this presentation is derived primarily from two sources:

Enoka, R. M. (1994). Neuromechanical basis of kinesiology. (2nd ed.). Champaign, Il: Human Kinetics.

Nordin, M. & Frankel, V. H. (2001). Basic Biomechanics of the Musculoskeletal System. (3rd ed.). Philadelphia:

Lippincott Williams & Wilkins.


What do you know about the macroscopic structure and function of tendons and ligaments l.jpg

What do you know about the macroscopic structure and function of tendons and ligaments?


What do you know about the microscopic structure and function of tendons and ligaments l.jpg

What do you know about the microscopic structure and function of tendons and ligaments?


Functions of ligaments and joint capsules l.jpg

connect bone to bone

act as static restraint to:

help with joint stability

guide joint motion

prevent excessive motion

Functions of Ligaments and Joint Capsules


Functions of tendons l.jpg

connect muscle to bone

transmit tensile loads from muscle to bone to:

produce joint torque

stabilize joint during isometric contractions and in opposition to other torques

cause joint motion during isotonic contractions

act as a dynamic joint restraint

interact with ligaments and joint capsule to mitigate loads that they receive

-----------------------------------------------------

Interesting points:

tendon extends the reach of muscle

tendon may conserve muscle tissue mass (i.e., muscle tissue not required to extend from origin to insertion)

Functions of Tendons


Tendons and ligaments l.jpg

Dense connective tissues (parallel-fibered collagenous tissues)

Sparsely vascularized

Composed primarily of collagen (fibrous protein which gives tendons and ligaments strength and flexibility)

Consist of relatively few cells or fibroblasts (≈ 20% of total tissue volume)

Contain abundant extracellular matrix

≈80% of total tissue volume

≈70% of extracellular matrix is water and ≈30% solids (collagen (≈75% of extracellular matrix), ground substance, and small amount of elastin)

Structure and chemical composition identical to other animal species (extrapolate behavior from animals)

Tendons and Ligaments


Tendons and ligaments7 l.jpg

Tendons

Join muscle to bone

Organization of collagen fibers to accommodate specialized function

Fibers longitudinal and parallel

Transmit tensile muscle forces

Ligaments

Join bone to bone

Organization of collagen fibers to accommodate specialized function

Fibers generally longitudinal and parallel, some oblique and spiral

Primarily transmit forces in functional direction, but also multidirectional

Tendons and Ligaments


How can you make string able to support a large load l.jpg

How can you make string able to support a large load?


How do manufacturers of string make it able to support a large load l.jpg

How do manufacturers of string make it able to support a large load?


Collagen molecule l.jpg

Collagen Molecule

  • Synthesized by within fibroblast as procollagen (precursor to collagen)

  • Consists of 3 polypeptide chains ( chains) each coiled in left hand helix

  • 3  chains combined in a right handed triple helix

  • Bonding (cross-linking) between  chains enhances strength of collagen molecules

  • Develops extracellularly into collagen molecules


Collagen l.jpg

Collagen

  • Groups of 5 collagen molecules form microfibrils

  • Cross links formed between collagen molecules that aggregate at the fibril level

  • Cross links between collagen molecules give strength to tissues (e.g., tendons and ligaments) they compose

  • Fibrils aggregate further to form collagen fibers

  • Fibers aggregate to form bundles


Collagen fiber arrangement in tendons and ligaments l.jpg

Collagen Fiber Arrangement in Tendons and Ligaments


Macroscopic and microscopic structure of tendon and ligaments l.jpg

Macroscopic and Microscopic Structure of Tendon and Ligaments


Macroscopic and microscopic structure of tendon and ligaments14 l.jpg

Macroscopic and Microscopic Structure of Tendon and Ligaments


Macroscopic and microscopic structure of tendon and ligaments15 l.jpg

Macroscopic and Microscopic Structure of Tendon and Ligaments

  • Epitendidium -outer covering

  • Fascicle - bundle of fibrils

  • Fibril - basic load bearing unit of tendon and ligaments

  • Microfibril - 5 rows of triple helixes in parallel (see figure)


Schematic illustration depicting the hierarchical structure of collagen in ligament midsubstance l.jpg

Schematic illustration depicting the hierarchical structure of collagen in ligament midsubstance


Macroscopic and microscopic structure of tendon l.jpg

Macroscopic and Microscopic Structure of Tendon


Slide19 l.jpg

Schematic representation of the microarchitecture of a tendon


Slide20 l.jpg

Structural hierarchy of a tendon. Connective tissue layers or sheaths envelop the collagen fascicles (endotenon), bundles of fascicles (epitenon), and the entire tendon (paratenon)


Macroscopic and microscopic structure of tendon and ligaments21 l.jpg

Macroscopic and Microscopic Structure of Tendon and Ligaments

  • Collagen molecule - triple helix in series; 5 rows stacked side-by side (parallel)

  • Triple helix - cross links occur both between and within rows of triple helixes  strength (# and state of cross links influence strength)  determined by age, gender, and activity level


Elastin l.jpg

Elastin

  • tendons and ligaments contain protein elastin

  • influences elastic properties of tendons and ligaments (↑ elastin  ↑ elasticity)

  • proportion varies by function

    • little in tendons and extremity ligaments

    • much present in ligamentum flavum between laminae of vertabrae

      • protect spinal nerve roots

      • pre-stress the motion segment

      • provide intrinsic stability to spine


Ground substance l.jpg

Ground Substance

  • amorphous material in which structural elements occur

  • in connective tissues, composed of proteoglycans, plasma constituents, metabolites, water, and ions between cells and fibers

Ground Substance in Tendons and Ligaments

  • Proteoglycans act as cement-like substance between collagen microfibrils contributing to overall strength of tendons and ligaments


Water and proteoglycans l.jpg

Water and Proteoglycans

  • Forms a gel

  • Viscosity decreases with activity

    • Thixotrophy (property seen in catsup)

    • Increased ability to accommodate higher velocity stretches

    • Advantage of a warm-up


Vascularization of tendons and ligaments l.jpg

Vascularization of Tendons and Ligaments

  • Ligaments

    • Vascularity

      • Originates from ligament insertion sites

      • Small size and limited blood flow

  • Dual Pathway for Tendons

    • Vascular (tendon surrounded by paratenon)

      • receives blood supply from vessels in perimysium, periosteal insertion, and surrounding tissues

    • Avascular (tendon surrounded by tendon sheath)

      • Synovial diffusion

      • Healing and repair in the absence of blood supply

----------------------------------------------------------------

Take home message:

  • Amount of tissue vascularization is directly related to rate of tissue metabolism and healing

  • Tendons and ligaments have limited vascularization


Macroscopic and microscopic structure of tendon and ligaments26 l.jpg

Macroscopic and Microscopic Structure of Tendon and Ligaments

  • Ligaments surrounded by very loosely structured connective tissue (not named)

    • Vascularity

      • Originates from ligament insertion sites

      • Small size and limited blood flow

  • Tendons surrounded by loose connective tissue (paratenon)

    • Paratenon forms sheath

      • Protects tendon

      • Enhances gliding

    • Epitenon

      • Synovial-like membrane beneath paratenon in locations of high friction

      • Absent in low friction locations

      • Surrounds several fiber bundles

    • Endotendon

      • Surrounds each fiber bundle

      • Joins musculotendinous junction into perimysium


Tendon insertion in bone l.jpg

Tendon Insertion in Bone


What comes to mind when you hear the word toe l.jpg

What comes to mind when you hear the word “toe”?


Load deformation relationships in collagenous tissues l.jpg

Load Deformation Relationships in Collagenous Tissues

  • Toe - collagen fibrils stretched to line up, from zigzag to straighten

  • linear region - elastic capability of tissue; elastic modulus

  • failure region - fibers disrupted

  • Hysteresis – failure to return to resting length


Stress strain relationship in collagenous tissues l.jpg

Stress-Strain Relationship in Collagenous Tissues


Collagen fibers unloaded toe and loaded elastic region l.jpg

Collagen Fibers – Unloaded (Toe) and Loaded (Elastic Region)


Typical load elongation curve l.jpg

Typical Load-Elongation Curve


Load elongation curve of ligaments with high levels of elastin l.jpg

Load-Elongation Curve of Ligaments with High Levels of Elastin

  • Elastin (protein) scarcely present in tendons and extremity ligaments

  • Ligamentum flavum:

  • Substantial proportion of elastin

  • Connect laminae of adjacent vertebrae

  • Function to protect spinal nerve roots

  • Provide intrinsic stability to spine


Load deformation relationships for connective tissues l.jpg

Load-Deformation Relationships for Connective Tissues

* 1kN = 224.8 pounds

Note that text gives value of failure of ACL between 76.4 and 87.67 lbs (340-390 N)


Is there any movement in isometric contractions l.jpg

Is there any movement in isometric contractions?


Physiological loading of tendons and ligaments l.jpg

Physiological Loading of Tendons and Ligaments

  • P (max) of ligaments and tendons not achieved during normal activities

  • normally 30% of P (max) achieved

  • upper limit during running and jumping  2 - 5 % P (max)


Ligament and tendon injury mechanisms l.jpg

Ligament and Tendon Injury Mechanisms

  • Injury mechanisms similar in tendons and ligaments

  • Microfailures take place before yield point

  • After yield point, gross failure results and joint begins to displace abnormally

  • Joint displacement can also damage surrounding structures (e.g., joint capsule, other ligaments, blood vessels)


Anterior drawer loading the acl to failure l.jpg

Anterior Drawer Loading the ACL to Failure


Anterior drawer loading the acl to failure42 l.jpg

Anterior Drawer Loading the ACL to Failure

  • Microfailure begins before physiological loading range is exceded


Slide43 l.jpg

What is the numerical categorization system used by athletic trainers to differentiate between levels of ligamentous injury?


Categorization of ligamentous injury l.jpg

Categorization of Ligamentous Injury

  • Negligible clinical symptoms, some pain, microfailure of some collagen fibers

  • Severe pain, clinical detection of some joint instability, progressive collagen fiber failure resulting in partial ligament rupture, strength and stiffness may decrease 50% or more, muscle guarding, perform clinical testing under anesthesia


Categorization of ligamentous injury45 l.jpg

Categorization of Ligamentous Injury

3.Severe pain, joint completely unstable, most collagen fibers ruptured, loading joint produces abnormally high stress on the articular cartilage  correlated with osteoarthritis


Additional factors in injuries to tendons l.jpg

Additional Factors in Injuries to Tendons

  • Amount of force of contraction produced by muscle attached to tendon

    • Tensile stress on tendon directly related to force of muscle contraction

    • High levels of tensile stress can be produced by eccentric contraction, possibly reaching failure


Additional factors in injuries to tendons47 l.jpg

Additional Factors in Injuries to Tendons

  • Cross sectional area of tendon in relation to cross sectional area of its muscle

    • Cross sectional area of muscle directly related to force of contraction

    • Cross sectional area of tendon directly related to tensile strength

    • Tensile strength of healthy tendon may be more than twice that of force of muscle contraction (clinically, muscle ruptures more common than tendon ruptures)

    • Large muscles usually have large tendons


Viscoelastic behavior rate dependency in tendons and ligaments l.jpg

Viscoelastic Behavior (Rate Dependency) in Tendons and Ligaments

  • Increased strain  increased slope of stress-strain curve (i.e., greater stiffness at higher strain)

  • Higher strain rate  more energy stored, require more force to rupture, undergo greater elongation


Slide49 l.jpg

Typical loading (top and unloading curves (bottom) from tensile testing of knee ligaments. The two nonlinear curves, called the area of historesis, represents the energy losses within the tissue.


Two standard tests of viscoelastic behavior l.jpg

Two Standard Tests of Viscoelastic Behavior*

  • Stress-relaxation test

    • Loading halted in safe region of stress-strain curve

    • Strain kept constant over extended period of time

    • Stress decreases rapidly at first, then gradually

    • Decrease in stress less pronounced with repeat tests

*Viscoelastic – variation in mechanical properties of tissue with different rates of loading


If you were asked to develop a creep test what would you use to make measurements l.jpg

If you were asked to develop a creep test, what would you use to make measurements?


Two standard tests of viscoelastic behavior53 l.jpg

Two Standard Tests of Viscoelastic Behavior

2.Creep test

  • Loading halted in safe region of stress-strain curve

  • Stress kept constant over extended period of time

  • Strain increases rapidly at first, then gradually

  • Clinically used in casting club foot and bracing in scoliosis


Slide54 l.jpg

Schematic creep curve for ligament


Influence of loading rates on bone ligament bone complex l.jpg

Influence of Loading Rates on Bone-Ligament-Bone Complex

  • At slow loading rates (60 sec.; much slower than in vivo injury mechanism), avulsion produced

  • At fast loading rates (0.6 sec.; simulates in vivo injury mechanism), ligamentous injury typical


Factors affecting biomechanical properties of tendons and ligaments l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Maturation and aging

    • Up to 20 years of age,

      • number and quality of cross-links in collagen molecules increases  increased tensile strength

      • Collagen fibril diameter increased  increased tensile strength

    • After maturation,

      • Collagen content of tendon and ligaments decreases  decreased tensile strength


Factors affecting biomechanical properties of tendons and ligaments58 l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Pregnancy and postpartum period

    • Clinical observation – increased laxity of tendons and ligaments in pubic area during latter stages of pregnancy and during early postpartum period  hormonal influence

    • Research studies of rats– increased laxity of tendons and pubic symphasis during latter stages of pregnancy and during postpartum period; stiffness of these structures later returned


Factors affecting biomechanical properties of tendons and ligaments59 l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Pregnancy and postpartum period (continued)

    • Hormones may have influence on ligament laxity in women at various stages of menstrual cycle  influence ligamentous injury rates in females (e.g., higher incidence of injury in women in basketball and soccer in comparison to men)


Factors affecting biomechanical properties of tendons and ligaments60 l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Mobilization and immobilization

    • Tendons and ligaments remodel in response to mechanical demands

      • Become stronger and stiffer when subjected to increased stress

      • Become weaker and less stiff when stress removed

    • Physical training found to increase tensile strength of tendons and ligament-bone interface


Factors affecting biomechanical properties of tendons and ligaments61 l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Mobilization and immobilization

    • Immobilization found to decrease tensile strength of ligaments

    • Immobilization decreased mechanical properties of bone-ligament-bone complex in knee of primates (8 weeks of casting)

    • Considerable reconditioning required in primate knees to regain former complex strength (approx. 12 months) (see figure)


Influence of immobilization on primate acl ligament l.jpg

Influence of Immobilization on Primate ACL Ligament


Influence of immobilization on primate acl ligament63 l.jpg

Influence of Immobilization on Primate ACL Ligament


Factors affecting biomechanical properties of tendons and ligaments64 l.jpg

Factors Affecting Biomechanical Properties of Tendons and Ligaments

  • Nonsteroidal Anti-Inflammatory Drugs (NSAID) (e.g., aspirin, acetaminophen, indomethacin)

    • In animal studies, short term administration of NSAIDs (indomethacin) found to increase the rate of biomechanical restoration of tissues (tendons)


  • Login