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Biomechanics > Week 5: Joint and Arthroplasty Biomechanics > Flashcards

Week 5: Joint and Arthroplasty Biomechanics Flashcards

1
Q

How do you biomechanically test joints?

A

In a similar way to the mechanical testing of tissue:

  • Torque-deflection relationship about 3 axes
  • Tension, compression, translation force-displacement relationships
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2
Q

Why would you use joint mechanics? (4 ways)

A
  • To design/test prosthetic implants (ability to restore function and replicate normal joint biomechanics)
  • To investigate injury thresholds
  • To investigate effects of injury/disease/treatment on joint biomechanics (e.g. selective cutting of ligaments)
  • To investigate comparative biomechanics (age/gender/species differences)
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3
Q

The analysis of human movement is separated into two components. What are they?

A

Gross movement of limb segments (gait) Detailed assessment of joint motion.

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4
Q

When observing motion, what view do you look at?

A

Look AT the plane, DOWN the axis

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5
Q

What is range of motion?

A

The range of motion (ROM) of a joint is the quantities that indicate two points at the extreme range of physiologic rotation and translation for each of the joint’s six degrees of freedom.

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6
Q

What 4 factors affect the range of motion?

A

Soft tissue restraints, number of joint axes, joint architecture, position of adjacent tissue.

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7
Q

Difference between flexion, extension, abduction, adduction, internal and external rotation?

A

Flexion: decreasing angle of a joint
Extension: increasing angle of a joint
Abduction: moving joint away from the body
Adduction: moving a joint towards the body
Rotation: moving a bone about a joint

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8
Q

What are degrees of freedom?

A
  • The body is composed of numerous uniaxial, biaxial and multiaxial joints
  • # Degrees of freedom refers to the ability to move in planes
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9
Q

Factors affecting the degrees of freedom?

A

Depends on;

  • Shape of articular surface
  • Number of ligaments
  • Motion of adjacent joints.
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10
Q

What are axes of rotation?

A

Rotational degrees of freedom.

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11
Q

What is combined movement?

A

Simple translatory motions of a body part involve movements of more than one joint.

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12
Q

What is stability?

A

Maintaining joint integrity

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13
Q

What provides joint stability?

A
  • Joint construction
  • Ligaments
  • Capsule
  • Tendons
  • Gravity
  • Vacuum in joint
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14
Q

What is flexibility?

A

Describes the range of movement within a joint

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15
Q

What factors affect flexibility?

A
  • Shape of the articular surface
  • Muscle mass
  • Bony blocks
  • Muscle length/flexibility
  • Ligament length/flexibility
  • Age
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16
Q

What is In-Plane motion?

A

Motion in which all coordinates of a rigid body move parallel to a fixed point. Has 3 degrees of freedom.

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17
Q

On Page 6 of the Lecture, what is the sagittal plane motion at the knee during the phase from A to B.

A

The joint action, or the displacement would be called extension.

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18
Q

On Page 7 of the lectures, what movement is occurring?

A

Flexion

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19
Q

In the pelvis, can flexion occur in more than one way?

A

Flexion can occur when the pelvis rotates toward the femur, or when the femur rotates towards the pelvis.

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20
Q

On slide 9, give an example when this type of motion can occur?

A

During golf swing

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21
Q

During what axis does movement most commonly occur?

A

Oblique Axis

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22
Q

What is the difference between degrees of freedom and range of movement?

A

Degrees of freedom refers to the ability to move in planes. Range of movement is dependent upon soft tissue restraints, number of joint axes, joint architecture, and size and position of adjacent tissue E.G the knee has one degree of freedom and a relatively large range of motion.

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23
Q

What movement is required in order for a person to move their finger in a straight line?

A

Simple translatory motions involve movent of more than one joint. The finger moves in a straight line when the wrist and elbow are not fixed.

Therefore human motion can be described as translatory motion that has major contributions from linear, angular, and curvilinear motions.

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24
Q

What is the image showing?

Will dislocation occur?

A

The image is of the glenohumeral joint. The joint willl not dislocate as long as the net humeral joint reaction force is directed within the effective glenoid arc (pink)Attach Sounds

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25
Q

What is the instantaneous axis of rotation?

A

At this point, if a line is drawn so that it is perpendicular to the line of motion, this is the instantaneous axis of rotation

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26
Q

What is out of plane motion?

A

Motion that moves in more than 1 single plane.

Motion with 3 degrees of freedom consisting of two rotations about mutually perpendicular axes and a translation perpendicular to the plane formed by the axes.

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27
Q

How is a reference system for measuring joint position chosen?

A

Is the position in which most joints in the body are at 0 degrees.

Usually, it is the position of the distal segment at the joint that defines the zero degree reference point. This can be seen in the picture.

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28
Q

What is the reference point fo rthe ankle?

A

Unlike the majority of joints, the anatomical position for the ankle is 90 degrees.

As the foot dorsiflexes, it gets closer to zero degrees. In this case, the proximal segment is considered the zero point instead of the distal segment, as is the case at most joints.

29
Q

What is the neutral position of the radioulnar joint?

A

Seen in the middle of the figure.

30
Q

What are the different types of joint classifications?

A

Functional

Structural

31
Q

What is the structural joint classification?

A
  • it’s when you classify the joints based on anatomical characteristics such as:
    • presence/absence of a joint cavity
    • type of connective tissue that binds them
32
Q

What are the types of joints when classified structrally?

A
  • Fibrous
  • Cartilaginous
  • Synovial
33
Q

What is the Functional joint classification?

A

It’s when joints are classified depending on the movement they permit

34
Q

What are the types of functional joints?

A

A. Synarthrosis-Immoveable joint
B. Amphiarthrosis-Slightly moveable joint
C. Diarthrosis-Freely moveable joint

35
Q

What is a synathrodial joint?

Give Examples of synarthroidal joints?

A

Its an immovable fibrous joint which can attenuate force with litttle or no movement

Examples include:

  • Sutures of cranial bones
  • Sockets of the teeth
  • Syndesmoses: radioulnar, tibiofibular.
36
Q

What is an amphiarthrodial joint?

Name Examples.

A

cartilagenous joint that attenuates force

Examples include:

  • Sychondroses: SC joint
  • Symphysis: Vertebral Joint, Pubic Symphysis
37
Q

What is a diarthrodial Joint

A

It provides mobility by permitting one body segment to rotate about another. It transmits one force segment to another.

Example: Ball and socket joint

38
Q

What is the anatomy of a Diathrodial Joint?

A

A Diathrodial Joint has

  • Articular Cartilage
  • Articular Capsule
    • Fibrous membrane
    • Synovial membrane
  • Synovial Fluid
  • Ligament
39
Q

What are the main types of Diathrodial Joint?

A
  1. Ball and socket (humeroscapular_
  2. Hinge Joint (Humeroulnar)
  3. Saddle Joint (Carpometacarpal I)
  4. Pivot Joint (radiooulnar)
  5. Gliding Joint (intercarpal)
  6. Condyloid Joint (Metacarpophalangeal)
40
Q

What are the characteristics of a synovial Joint?

A
  • Freely moveable (lots of movement)
  • Cartilage and ligament for stability
  • Synovial membrane (produces fluid)
  • Synovial fluid (lubricates the joint)
41
Q

What type of joints are the following?

  • shoulder
  • elbow
  • wrist
  • hip
  • knee
  • ankle?
A
42
Q

What bones make up the following joints?

  • Shoulder (3)
  • Elbow (3)
  • Wrist (3)
  • Hip (2)
  • Knee (3)
  • Ankle (3)
A

Shoulder

  1. Clavicle
  2. Humerous
  3. Scapula

Elbow

  1. Humerous
  2. Radial
  3. Ulna

Wrist

  1. Radius
  2. Ulna
  3. carpals

Hip

  1. Femur
  2. Pelvis

Knee

  1. Fibula
  2. Femur
  3. Tibia

Ankle

  1. Tibia
  2. Tarsals
  3. Fibula
43
Q

What Muscles make up the following joints?

Shoulder (5)

Elbow (2)

Wrist (2)

Hip (3)

Knee (2)

Ankle (3)

A

Shoulder (5)

  1. Deltoid
  2. Pectorals
  3. Trapezius

Elbow (2)

Bicep

  1. Tricep
  2. Wrist (2)

Hip (3)

  1. Hip Flexors (iliopsoas)
  2. Gluteals
  3. Adductors
  4. Abductors

Knee (2)

  1. Quadricepts
  2. Hamstring

Ankle (3)

  1. Gastocnemius
  2. soleus
  3. Tibialis anterior
44
Q

Do muscles always work in pairs? Explain?

A

Yes. The agonist contracts while the antagonist relaxes

e.g During elbow flexion: biceps (agonist) triceps (antagonist)

45
Q

What is the role of muscles?

A

To provide movement and stability

46
Q

What factors affect the functionality of muscles?

A
  1. Length of lever arms
  2. range and force developed by each muscle
  3. stretched condition of contracting muscle
  4. individual angles of muscle pull
  5. site of muscle relative to joint axis
  6. action of synergic and antagonistic muscles
47
Q

What is prontation and supination?

A
48
Q

What is dorsiflexion and plantarflexion?

A
49
Q

What movement is possible at the following joints:

  • shoulder
  • elbow
  • hip
  • knee
  • ankle
A
  • shoulder
    • flexion
    • extension
    • abduction
    • adduction
    • rotation
  • elbow
    • flexion
    • extension
  • hip
    • flexion
    • extension
    • abduction
    • adduction
    • rotation
  • knee
    • flexion
    • extension
    • slight internal rotation on extension
  • ankle
    • dorsi flexion
    • plantar flexion
50
Q

What is the centre of gravity?

A

Point at which all parts of the body are equally balanced.

51
Q

What is the line of gravity?

A

It’s the direct line from the centre of gravity to the ground

52
Q

Fill out the following:

Someone is more ________ when they have a ________ centre of ________ , a ________ base of ________ and a line of gravity that falls ________ the body.

  • low
  • wide
  • within
  • balanced
  • gravity
  • support
A

Someone is more balanced when they have a low centre of gravity, a wide base of support and a line of gravity that falls within the body.

53
Q

What is the point of application of a force?

A

It’s the point at which the force is applied.

e.g. a muscles attachment to a bony lever.

Technically, it’s the point of intersection of the line of force and mechanical axis of the bone.

54
Q

What is the muscle angle of pull?

A
55
Q

How do you determine the direction of muscular force?

A

It’s the direction of the line of pull of the muscle.

56
Q

What is the relationship between linear and angular velocitY?

A

Two points can have the same angular velocity, but their linear velocity may differ depending on the legnth of the lever arm.

For example, if the lever arm is bigger, the point will move further and therefore have a larger linear velocity.

57
Q

What is momentum

A

Amount of motion that an object has

58
Q

What is a lever?

A

A rigid bar that can rotate about a fixed point when a force is applied to overcome a resistance

59
Q

Why are levers used?

A
  1. Overcome a resistance larger than the magnitude of the effort applied
  2. Increase the speed and range of motion through which a resistance can be moved
60
Q

What is the fulcrum in the body?

What is the force?

A

The Fulcrum is the joint

The force is the contracting muscles

61
Q

What is the effort arm and resistance arm?

A
  • Effort arm (EA): Perpendicular distance between fulcrum & line of force of effort
  • Resistance arm (RA): Perpendicular distance between fulcrum & line of resistance force
62
Q

Draw the 3 types of levers

GIve an example for each lever

A
63
Q

Why is walking down stairs more difficult than up for someone with patellofemoral problems?

A

The amount of force exerted on the knee cap while climbing down the stairs is almost about three and half times the body weight.

The patella has a lining of cartilage meant to protect the kneecap to withstand huge percentages of comprehensive forces. However when anything which interferes with the way the kneecap moves, the force exerted on the kneecap is greatly magnified. This is why walking downstairs causes more knee pain.

64
Q
  1. Why is standing up from a stool easier than from a low toilet?
  2. Why is sitting easier than standing from the seated position?
  3. Why does a person with severe chronic obstructive pulmonary disease need to lean forward and support their upper extremities to breath when the diaphragm is flat?
A
  1. Have to move greater distance (guessed)
  2. Need to overcome your weight to lift (guessed)
  3. Bending at the waist helps the diaphragm move more easily, allowing air enter the lungs. hold onto your upper body to assist diaphragm movement.
65
Q

How is the performance of an implant assessed?

A
  • How much of the ROM is restored (i.e. any hindrances on flexibility)
  • How the stiffness changes (i.e. muscular effort to move the joint)
  • Does the neutral zone increase? (i.e is the joint more stable, prone to injury/pain?)
  • Does the device mimic the natural biomechanics of the joint (i.e. constrained motion may increase wear and tear of the device)
66
Q

What implant testing methods are there?

A
67
Q

Q:What tests should be done for verification of a fracture screw?

A
  1. Mechanical tests:
    * What load/torque can be applied before the screw fails
  2. Biocompatibility tests
68
Q

Spine implant example

  1. Axial compression stress?
  2. Safety factor loading
  3. Lifting free body diagram
  4. Lever systems and moments in lifting
  5. Optimization to reduce stress/wear?
A
  • Half of your body weight is passing through the L5 joint
  • How much stress passing through the mobile bearing?
    • Look at cross sectional area
    • Stress = F/A
    • Use the smaller radius
  • Safety factor loading
    • Do the calculation with 120kg person, account for 20% more, see what stress needs to be held here, choose a material that needs to account for that safety margin
  • fbd attached
  • optimize by choosing correct material

Biomechanics (5 decks)

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