Ligaments And Tendons Flashcards
A bone-ligament or bone-tendon complex.
Enthesis
What is the overall function of an enthesis?
The progressive change from ligament/tendon to
bone protects against injury by allowing
better stress absorption and
transmission
What are the structural (mechanical) jobs of ligaments?
- Stabilize joints (at end range)
- Guide joint motion
- Prevent excessive motion
What are the functional (sensory) jobs of ligaments?
- detect rate and vectors of load via mechanoreceptors
- detect tissue damage via nociceptors
What are the structural (mechanical) jobs of tendons?
- 99.9% collagen for strength, stiffness, ductility
- Parallel arrangement to transmit tensile strength
What are the functional (sensory) jobs of tendons?
- Attach muscle to bone
- transmit tensile loads from muscle to bone for the purpose of joint motion and stabilization
The quality whereby a material exhibits large plastic deformation before FAILURE.
FAILURE > 5% total elongation of
material
Ductility
The quality whereby a material exhibits little plastic deformation before FAILURE.
FAILURE < 5% total elongation of
material
Brittleness
What is a deformation of a viscoelastic material
with time, when the load remains constant that results in a gradual rearrangement of collagen,
proteoglycans and water molecules?
Creep
What is the creep-relaxation phenomenon?
The deformation of viscoelastic material over time due to constant load. Over time, the tissue relaxes into its new length to decreases load over time. Results from stretching of tissue.
Ex: force needed to hold down a branch over time will decrease.
What are short term effects of a sprain?
- temporary changes like hysteresis and slow return to baseline length
- pain
What are long term effects of a sprain?
- hypermobolity and instability
- degeneration of joints
- susceptibility to further injury
Strength of a ligament depends on what factors?
- fiber composition (more collagen = stronger)
- size and shape of fibers (increased fiber diameter and # of fibers = increased strength)
- orientation of fibers (fibers parallel to direction of tension = more strength)
- speed of loading (strength of tissue increases with speed of loading)
Of tendons, ligament and skin, rate them in order from strongest to weakest
Tendons > ligaments > skin
What types of injury can occur to ligaments?
- sprain (% deformation has reached the plastic range and results in permanent deformation)
- tear (% deformation exceeds plastic range/maximum stretch and tissue fails, resulting in lose of original form and energy)
NOTE: microfailure of collagen can occur in the elastic range and is the beginning of a grade 1 sprain but does not actually sprain until plastic region
Progressive failure of collagen fibers with no change in gross appearance is seen in what type of ligament damage?
Grade 1 sprain
Tensile failure of collagen fibers and shear failure between fibers is seen is what type of ligament injury?
Grade 2 sprain - gross failure of ultimate loading. This injury results in:
- partial rupture
- joint instability
- 50% decrease in strength
- severe pain and swelling
Complete rupture, instability and dislocation is seen in what type of ligament injury?
Grade 3 sprain - complete failure with tissue loading that is characterized by severe pain initially but followed by little to no pain.
How does loading speed affect injury?
Both the magnitude of the load and the rate that the load is applied affects injury. The strength of tissue (both bone and ligament) increases with speed but the bone increases more than the strength of the ligament, therefore the ligament fails first
What are the characteristics of physiological loading of tendons and ligaments?
- Under normal physiological conditions, the tensile load (stress) is only about 1/3 of its strength capacity.
- But high loads (trauma) or repetitive loads or sustained loads can result in injury.
What are the characteristics of the ligamentum flavum?
- composed of 2/3 elastic fibers
- functions to absorb shock and protect nerve roots and spinal cord
- elongation reaches 50% before stiffness significantly increased
- failure is at 70% elongation
A high loading speed to the ACL will result in what type of damage?
- ligament tears 2/3s of the time
- bone allusion in 1/3s of the time
A low loading speed (1 minute) to the ACL will result in what type of damage?
- bone avulsion
Why is exercise needed during ligament remodeling?
Recovering ligament/tendon becomes:
- stronger and stiffer with increased stress
- weaker and less stiff with decreased stress
Strenuous exercise for a year after injury can increased the maximum load to failure, increase stiffness and increase the energy storage capacity of the tissue. This will result in tissue more resistant to re injury
