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Unit 2 > Orthopaedic Biomechanics 1 (10/11b) [Biomedical] > Flashcards

Orthopaedic Biomechanics 1 (10/11b) [Biomedical] Flashcards

1
Q

Force

A

push or pull that produces, arrests or modifies movement

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2
Q

Torque

A

product of a force and its moment arm (EX: rotational force)

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3
Q

Forces and torques are both ___ or ___, and occur simultaneously

A

internal or external

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4
Q

Load

A

a force that acts on the body

Externally derived loads — gravity, impact, friction, wind

Internally derived loads — muscle activation, tissue deformation (EX: stretch, compression

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5
Q

Tissue Loading

A

Joint reaction forces load different tissues

Tissue deform as much as they need to to accommodate stretching or compressing, results in loads arising within tissues

Cumulative loading can lead to eventual injury

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6
Q

How do healthy tissues respond to load?

A

Can deform but resist change in structure and shape

Internal forces that arise within the structure under load can resist the external forces placing the tissue under the load

Load response is tissue dependent

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7
Q

Tissue Stress

A

Force or load generated within the tissue to resists deformation, divided by its cross sectional area

A measure of load or energy that stored within a tissue

Pressure = Force (N) /Area (m2)

EX: in a balloon → forces resisting being stretched out/expanded

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8
Q

Tissue Strain

A

The amount a tissue deforms under a force or load

Usually expressed as a percent change in length (%), distance (mm), although truly a unit less measure

EX: in a balloon → measure of how much the balloon stretches/expands

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9
Q

Stress Strain Diagram - Toe Region

A

represents taking up slack in the tissue

the nonlinear beginning of the diagram

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10
Q

Stress Strain Diagram - Slope of Linear Region

A

represents stiffness of the tissue

Young’s Modulus

the linear upward slope of the diagram

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11
Q

Stress Strain Diagram - Young’s Modulus (ε)

A

represents how much the tissue deforms in response to certain loads (aka stiffness)

High ε = high stiffness
Low ε = low stiffness

This behavior only exists in linear slope region of elastic region

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12
Q

Stress Strain Diagram - Elastic Region

A

represents elastic deformation energy

Tissue returns to original shape/length after loading

All stored energy is released once tissue is unloaded

dark blue region of the diagram

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13
Q

Stress Strain Diagram - Yield Point

A

represents the transition between elastic and plastic behavior

Point of no return (aka once you pass this point, you create permanent tissue change)

Additional load results in marginal increase in stress

point where it goes from dark blue to light blue on the diagram

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14
Q

Stress Strain Diagram - Plastic Region

A

represents plastic deformation caused by micro-failure of tissue under continued load

Overstrained tissue is permanently deformed

Plastic deformation energy cannot be recovered once load is released

Can be good (EX: stretching, weight lifting, serial casting, joint mobilization) or bad (EX: injury)

light blue region of the diagram

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15
Q

Stress Strain Diagram - Ultimate Failure Point

A

represents point where tissue fails and is unable to hold additional load

point in light blue region where sharp downward slope begins

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16
Q

Biologic tissues exhibit ___-like and ___-like behaviors

A

fluid-like and elastic-like

17
Q

Biologic Tissues - Fluid Behaviors

A

Viscosity — fluid-like component to behavior of tissue, resistance to flow

EX: honey = high viscosity, water = low viscosity

Fluid-like behavior is a time dependent behavior

Slow loading can lead to stretching, fast loading can lead to tear (EX: silly putty)
- in general, not always the case

18
Q

Biologic Tissues - Elastic Behaviors

A

Elasticity — ability of material to return to original shape after loading

Does not mean “stretchy”, but rather a measure of how stiff/unstiff it is

19
Q

Bone, capsule and ligament, muscle, tendon, fibrocartilage, and articular cartilage all respond differently based on ___ ___

A

their makeup

20
Q

Tissues in the body are ___

A

viscoelastic

21
Q

Creep

A

continued deformation of a material over time as it’s subjected to a constant load

Prolonged, low load stretch

Time required depends on type of tissue

EX: serial casting → PT will use a cast to hold body in a certain position to force it to adapt to the stretch, and incrementally increase the stretch to improve motion

22
Q

Ankle Sprain Data

A

Most common cause is inversion plantarflexion

Most common injury in ankle is ATFL

23
Q

ACL Strain Data

A

It is usually a rapid load that causes an ACL tear

In vitro testing — in the lab testing, outside of the living organism

In vivo testing — in a living organism

In silica — completely computer modeled

24
Q

Factors that Impact Musculoskeletal Loads

A

Loading Magnitude
Loading Rate
Loading Type

25
Q

Loading Magnitude

A

how much the tissue is loaded

High vs Low Load

Cumulative load — you can keep increasing the yield capacity or reach yield capacity faster since you are starting at a higher load due to cumulatively loading or getting stronger

26
Q

Loading Rate

A

the speed at which a tissue is loaded

Loading rate is a function of time

Biologic tissues are sensitive to the rate at which they are loaded

Tissues behave differently under different loading rate conditions

Fast or slow loading rates lead to different injuries

EX: loading in the ACL

  • Fast/high velocity → leads to complete ACL rupture
  • Slow/low velocity → leads to intact ACL with avulsion of tibial eminence (ligament pulls away from tibia)
27
Q

Loading Type

A

the way in which the tissue is loaded

Tension, Compression, Bending, Shear, Torsion, Combined

28
Q

Loading Type - Tension

A

two forces pull on an object in different directions

EX: lateral ankle ligaments are severely tensioned as the foot rotates inward

29
Q

Loading Type - Compression

A

forces that push/pull surfaces of objects together, or brings the end of an object closer

EX: humerus is pulled against the glenoid by the deltoid muscle creating a compressive load between the bones

30
Q

Loading Type - Bending

A

deformation tissue that occurs at right angles to its longitudinal axis

Concave side undergoes compression load

Convex side undergoes tension load

EX: coxa vara results in increased bending load on neck of the femur

31
Q

Loading Type - Shear

A

unaligned parallel forces that move on part of a body in one direction and another part in the opposite direction

EX: cam type femoroacetabular impingement creates abnormal shear load between the femur and acetabulum, causing delamination (peeling off articular cartilage)

32
Q

Loading Type - Torsion

A

twisting force applied to tissue around longitudinal axis

EX: noncontact ACL rupture

33
Q

Loading Type - Combined

A

multiple types of loading interacting on the tissue

34
Q

Factors That Influence Tissue Ability to Accept Loads

A

Age
Disease/trauma
Overuse
Underuse

35
Q

Tissue Loading Ability - Age

A

cells in tissues change as we get older, which dictates tissue response

(EX: osteoporosis)

36
Q

Tissue Loading Ability - Disease/Trauma

A

soft tissue disorders influence genes that code for the protein of collagen, if this is impacted it affects elasticity of tissues

EX: Ehlers Danlos syndrome where tissues are overly stretchy and lack ability to return to normal shape

37
Q

Tissue Loading Ability - Overuse

A

when loading of the tissue exceeds the repair capacity of the tissue, leads to plastic deformation

Can cause microtearing which changes tissue, you may give time to rest but not enough time for tissue to go back to its baseline

EX: tendonitis

38
Q

Tissue Loading Ability - Underuse

A

when you don’t load tissue, it starts to lose its ability to accept loads

Changes, like loss of bone or muscle mass, can occur over time

Bone grows in response to stress — if you don’t load them, they will get weak

Unit 2 (27 decks)

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