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ANAT102 > Topic 1: Bones and Joints of the Shoulder region > Flashcards

Topic 1: Bones and Joints of the Shoulder region Flashcards

1
Q

4 joints of the shoulder joint

A
  1. Glenohumeral joint
  2. AC joint (acroclavicular)
  3. Sternoclavicular joint
    4.
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2
Q

Classification of the Glenohumeral (shoulder) joint

A

Synovial, multiaxial, ball & socket

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3
Q

Movements of the glenohumeral joint

A
  1. Flexion- extension (transverse axis)
  2. Abduction- adduction (anterioposterior axis)
  3. Internal (medial) - external (lateral) rotation (longitudinal axis)
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4
Q

Articular surface of the glenohumeral joint

A
  1. Humeral head - 1/2 sphere (covered with articular cartilage to increase stability)
  2. glenoid fossa - very shallow
    Only 25-30% contact between articular surfaces
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5
Q

Glenohumeral jt fun fact

A

less stable than hip joint but more mobile

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6
Q

Glenohumeral joint articular capsule

A

Very thin and lax –> aids mobility (enables more movements)

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7
Q

Glenohumeral Joint articular capsule attachments

A
  • medially to margin of glenoid fossa and glenoid labrum
  • laterally to margin of anatomical neck of humerus
  • reflected inferiorly onto medial shaft of humerus
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8
Q

Glenohumeral joint articular capsule reinforced by:

A
  1. rotator cuff tendons
  2. long head of triceps tendon
  3. glenohumeral and coracohumeral ligaments (capsular ligaments)
    Helps stabilise the shoulder
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9
Q

Glenohumeral joint articular capsule communicates with:

A
  1. subscapular bursa

2. intertubercular groove

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10
Q

Glenohumeral joint synovial membrane

A
  1. lines joint capsule
  2. lines bony surfaces inside joint
    capsule which are not covered by
    articular cartilage
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11
Q

Glenohumeral Joint- intra-articular structures

Glenoid Labrum

A

Fibrocartilaginous structure around glenoid fossa

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12
Q

Glenoid Labrum functions

A
  1. facilitate mobility –> increases SA of jt
  2. increases glenoid concavity- up to 50%
  3. provides attachment site for joint capsule, ligaments, muscles
  4. deepens socket to increase stability
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13
Q

Glenoid fossa bone bit fun fact

A

very small- needs other things to stabilise/ reinforce joint

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14
Q

Orientation of the glenoid fossa

A

When the arm is hanging, the glenoid fossa faces:
- laterally – because the arm= out to side
- slightly anteriorly– because most of our actions are infront of us
- slightly superiorly –because less energy for stability
Ensures stability of glenohumeral joint

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15
Q

Glenohumeral Joint- Ligaments

CORACOACROMIAL LIGAMENT

A
  • from coracoid process on scapular to acromion
  • prevents superior dislocation of humerus
  • provides “lid” on top of humerus
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16
Q

Coracohumeral joint Ligament

CORACOHUMERAL LIGAMENT

A
  • from root of coracoid process to greater tubercle (on humerus)
  • prevents lateral and therefore, inferior dislocation of humerus –> in hanging postn
    –> glenoid fossa directed superiorly
    –> upper limb pendant
    goes slack in movment –> no function in mvmt
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17
Q

Glenohumeral ligaments

A
  • From anterior glenoid rim to humerus (and capsular ligaments)
  • inconsistent
    1. superior 2. middle 3. Inferior
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18
Q

Glenohumeral ligaments- SUPERIOR

A
  1. prevents lateral and therefore, inferior dislocation of the humerus
  2. limits external rotation (because its anterior)
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19
Q

Glenohumeral ligaments- MIDDLE

A

Limits external rotation

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20
Q

Glenohumeral ligaments - INFERIOR

A
  1. prevents anterior dislocation of humerus when fully flexed/ abducted
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21
Q

Glenohumeral ligaments

TRANSVERSE HUMERAL

A
  1. passes between the humeral tubercles

2. holds long head of biceps brachii in the bicipital groove

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22
Q

Scapulothoracic Movements

A
  1. elevation- depression
  2. Abduction- adduction
  3. upward rotation (glenoid fossa up)- downward rotation
  4. internal rotation- external rotation
  5. anterior tilt- posterior tilt
  6. protraction
  7. retraction
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23
Q

Protraction combination movements

A
  1. abduction + internal rotation

e. g. squeeze arms forward

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24
Q

Retraction combination movements

A
  1. adduction + external rotation
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25
Q

Sternoclavicular joint classification

A

Synovial, multiaxial, plane

also called modified ball & socket

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26
Q

Sternoclavicular Joint articular surfaces

A
  1. sternal end of clavicle (male)
  2. clavicular notch of sternum (female)
  3. costal cartilage of rib 1
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27
Q

Sternoclavicular Joint articular capsule

A
  • strong

- reinforced by capsular ligaments

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28
Q

Sternoclavicular Joint

A

2 separate synovial membranes

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29
Q

Sternoclavicular Joint- intra articular disc

A
  1. assists in stability of SC joint

- vertical disc dividing joint cavity into medial and lateral compartments

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30
Q

Sternoclavicular Joint- intra articular disc functions

A
  1. shock absorber
  2. prevents superior dislocation of clavicle
    - thrusting forces
    - weight in hand
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31
Q

Sternoclavicular Joint Ligaments

COSTOCLAVICULAR LIGAMENT

A
  • bilaminar (two layers), running at 90 degrees to one another
  • limits elevation of clavicle
  • limits protraction and retraction
  • acts as a fulcrum/ pivot about which movements occur (for elevation of clavicle)
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32
Q

Sternoclavicular Joint Ligaments

ANTERIOR STERNOCLAVICULAR LIGAMENT

A

(from sternum to clavicle)

- limits retraction

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33
Q

Sternoclavicular Joint Ligaments

POSTERIOR STERNOCLAVICULAR LIGAMENT

A

(from sternum to clavicle)

- limits protraction

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34
Q

Sternoclavicular Joint Ligaments

INTERCLAVICULAR LIGAMENT

A

(between clavicles)

- limits clavicles popping up when downward force is applied

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35
Q

ACROMIOCLAVICULAR JOINT

Classification

A

Synovial, multiaxial, plane

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36
Q

ACROMIOCLAVICULAR JOINT

Articular Surfaces

A
  • acromial end of clavicle
  • anterior, medial acromion
    between lateral end of clavicle and acromial process
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37
Q

ACROMIOCLAVICULAR JOINT

Articular Capsule

A
  • loose
  • reinforced by capsular ligaments
  • -> intra-articular disc (shock absorber)
  • —–> partial disc which functions as a shock absorber
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38
Q

ACROMIOCLAVICULAR JOINT

Ligaments – Coraclavicular (CUNOID PART)

A 
(from coracoid to clavicle)
Conoid part (attaches to conoid tubercle)
- vertical 
- limits protraction of scapula
- produces axial rotation of clavicle
More medial
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39
Q

ACROMIOCLAVICULAR JOINT

Ligaments – Coraclavicular (TRAPEZOID PART)

A 
(attaches to trapezoid line)
- oblique fibres
- limits retraction of scapula
- prevents medial dislocation of scapula
more lateral
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40
Q

Pectoral Girdle

A
  1. scapula
  2. clavicle
  3. AC & SC joints
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41
Q

Pectoral girdle definition

A

Bone structure that attaches to the trunk

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42
Q

Glenoid fossa orientation

A
  1. anterior (little bits)
  2. lateral (lots)
  3. superior (little)
    part of the GH joint
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43
Q

Pectoral Girdle function

A

Increases the ROM for the shoulder joint

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44
Q

How does the pectoral girdle increase shoulder jt ROM?

A
  1. By changing the position of the glenoid fossa

2. due to clavicle acting as a strut (holding shoulder away from trunk)

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45
Q

What happens to ROM if no girdle?

A
  1. adbuction ROM drops from 180 to 120

2. flexion ROM drops form 180 to 120

46
Q

Why does glenoid fossa position matter so much?

A

Head of humerus articular surface = 3x larger than the glenoid fossa articular surface.
- must ensure that head of humerus remains in centre of glenoid fossa

47
Q

Stability of GH jt in pendant postn

A

Relies on passive structures (ligaments etc)

  • orientation of fossa
  • tension in ligaments and superior capsule
48
Q

Stability of GH jt as it abducts

A
  • orientation of fossa = ineffective
  • needs dynamic stability (not passive)
  • tension in ligaments and capsule reduced
49
Q

Glenohumeral joint stability- GF orientation

A

Lateral movement of humeral head = reduction in stability of GH joint
- can move inferiorly –> vulenerable to displacement
Structures prevent lateral movement of head of humerus & increase stability of GH jt

50
Q

Humeral head - GH stability (GF orientation)

A
  • structures that prevent lateral movement of humeral head

- prevent inferior movement of the humeral head –> increases stability

51
Q

Structures that prevent lateral movement of humeral head

A
  1. ligaments (coracohumeral, superior GH ligament)
  2. anything on top of GH increases stability and prevents lateral movement
    (lateral movement enables inferior displacement –> thus unstable; the normal orientation is so that the humeral head doesn’t move lateral and down, lip of bone)
52
Q

Functional significance of the position of GF in anatomical position

A
  • in AP, stability comes from passive structures (no energy reqd to maintain this)
  • once we move out of that; tension off from these stabilising structures (ligaments/ capsule)
  • –> NEED DYNAMIC STRUCTURES FOR STABILITY
53
Q

Shoulder joint classification

A

Synovial, multi-axial, ball and socket

54
Q

Shoulder joint movements

A
  1. flexion/ extension
  2. abd/ add
  3. medial/ internal rotation + lateral/ external rotation
  4. circumduction (flexion, abduction, extension, adduction/ reverse)
    - -> “making a cone in space”
55
Q

Scapulathoracic joint classification

A

not an anatomical joint– FUNCTIONAL JOINT

56
Q

Scapula facts

A
  • sits on thoracic cage
  • has AC jt laterally
  • otherwise, held in place by muscles “suspended by muscles”
57
Q

Scapula movements

A
  1. elevation & depression
  2. upward & downward rotation
  3. protraction & retraction
    NOT PURE MOVEMENTS – ALL INVOLVE A BIT OF THE OTHER MVMTS (not 1 in iso)
58
Q

Scapulothoracic joint

A
  1. NOT AN ANATOMICAL JOINT
    - no articular surfaces
    - no ligaments/ joint capsule
    - no synovial membrane
  2. IS A FUNCTIONAL JOINT (heavily contributes to movement)
    - the scapula moves on the thoracic cage (ribs)
    - fascia over the muscles permits movement (gliding & sliding of scap)
59
Q

Scapulothoracic joint contribution to full ROM for shoulder jt

60
Q

What moves over the scapula?

61
Q

Protraction of scapula

A

bring scaps forward – arms out infront

62
Q

retraction of scapula

A

squeezing something between shoulder blades - scaps go posterior

63
Q

Upward & downward rotation of the scapula

A

lifting bent arms up & down

- gleniod fossa faces up and down

64
Q

Upward & downward rotation of scapula

Point of reference

A

inferior angle of scap

65
Q

Upward & downward rotation of scapula

Point of interest

A

Glenoid Fossa

66
Q

Scapula & clavicle movements

A

Relative positions of scapula & clavicle must be able to change

  • occurs at AC joint
  • small amounts of movement medially, larger amounts laterally
67
Q

Clavicle movements in retraction

A

clavicle moves post

68
Q

Clavicle movements in protraction

A

Clavicle moves anteriorly

69
Q

Clavicle movements in elevation

A

Superiorly

70
Q

Clavicle movements in depression

A

comes back to lower position

71
Q

Contribution to movement by SC joint

A

scapula = moved by muscles–> moves scapula –> moves AC joint –> moves clavicle which is associated with the SC joint.
- movement of the scapula occurs because the other 1/2 of the clavicle is connected to the AC joint, which = connected to scapula –> MOVEMENT

72
Q

where does the clavicle have more movement?

73
Q

Scapulohumeral rhythm definition

A

Describes the movement relationship between the scapula and humerus

74
Q

Scapulohumeral rhythm movements

A

Upward rotation of the scapula and abduction/ flexion of the humerus synchronously

75
Q

Ratio of the “rhythm” of movements

A

2:1
GH: ST (scapulothoracic)

76
Q

Scapulohumeral Rhythm total range of abduction:

77
Q

Scapulohumeral Rhythm total range of abduction:

ST joint contribution

78
Q

Scapulohumeral Rhythm total range of abduction:

GH joint:

79
Q

“Rhythm” refers to:

A
  1. quality of movement
  2. equal R v L of patient
  3. how coordinated the movement it is
80
Q

Scapulohumeral rhythm initial scapula movement

A

little/ no movement in the first 30 degrees abduction

no change in inferior angle

81
Q

SH rhythm sequence:

A
  1. GH all time
  2. SC jt
  3. AC jt to continue to full ROM
82
Q

What is the SC joint motion associated with to do with the clavicle

A

Clavicular elevation

- costoclavicular (medial & inferior) ligament limits this

83
Q

What is the AC joint motion associated with to do with the clavicle

A

Rotation

- clavicle moves backward in abd –> rotated posteriorly

84
Q

Where are the SC & AC movements realised?

A

ST (scapulothoracic) joint

*realised = sum of movements & see movements

85
Q

What does scapulohumeral rhythm do?

A
  1. increases ROM of shoulder
    - head of humerus is rolling & gliding on a moving glenoid fossa
    - glenoid fossa moves by moving the scapula
  2. maintains muscles @ optimal length for effective contraction
    - deltoid
    - rotator cuff muscles –> increases stability throughout range
86
Q

What is optimal length?

A

Sarcomeres = just right length for contraction (length-tension relo from sem 1)

87
Q

Length tension relationship defintion

A

Direct relationship between the tension a muscle fibre can produce and the length of sarcomeres in the muscles

88
Q

Rotator Cuff muscles function

A

To provide dynamic stability at the shoulder joint by:

  1. taking up slack in the shoulder joint capsule during movement
  2. providing a medial force to the humeral head
    - -> to accurately position it in the centre of the glenoid fossa during shoulder movement (STABILISER)
89
Q

Anatomical actions of the Rotator cuff muscles

A

1 abductor (supraspinatus), 1 internal rotator (subscapularis), 2 external rotators (teres minor & infraspinatus)

90
Q

Rotator cuff muscles

A
  1. supraspinatus
  2. infraspinatus
  3. teres minor
  4. subscapularis
91
Q

Rotator cuff muscles synergist function

A
  • to cancel out unwanted rotation –> ensures head of humerus stays in centre of GF)
    subscapularis (anterior compartment of RC) - action = IR
    infraspinatus (posterior compartment of RC) - action = ER
    CANCEL EACHOTHER OUT
92
Q

Desired movement of the RC muscles

93
Q

Function of the deltoid muscle in RC

94
Q

What happens when the deltoid contracts in abduction?

A

Humeral head will glide superiorly –> we want it in the centre (turns on its stabiliser function)

95
Q

Synergists in rotator cuff muscles

A

inferior part of subscapularis cancels out rotations
inferior part of infrapsinatus cancels out rotations
teres minor - prevents superior glide of humeral head

96
Q

Function of scapular muscle e.g. upward rotation of the scapula
what does upward rotation accompany?

A
  • abduction &/or flexion of the shoulder joint – needs Scap
97
Q

What does upward rotation of the scapula do to the glenoid fossa?

A

Moves the GF; thus, increasing the mobility of the shoulder

- head of humerus still has space to move on glenoid fossa

98
Q

Upward rotation of the scapula RC muscles relo

A

Repositions them

  • lets them provide an appropriate stabilising force to the humeral head
  • throughout shoulder range of movement –> sarcomeres @ optimal length to stabilise head of humerus
  • maintaining their length-tension relationship
99
Q

Muscles which contract to produce upward rotation of the scapula

A

Trapezius & serratus anterior

100
Q

Serratus anterior actions

A

Protract & upwardly rotate scapula

101
Q

Upper trapezius actions

A

Elevate & upwardly rotate scapula

102
Q

Middle trapezius actions

A

retract scapula

103
Q

Lower trapezius actions

A

Depress & upwardly rotate scapula

- attachment to scap = close to superior angle; therefore, contraction = angular drop = upward rotation

104
Q

Serratus anterior location

A

Attaches on the medial border of scapula & runs superficial to subscapularis –> attaches anteriorly onto ribs

105
Q

Upper trapezius role in upward rotation of the scapula

A
  • mover/ agonist
  • synergist (cancel out depression from lower trap to leave it with just upward rotation)
    goal of muscle= to elevate scap –> thus cancel out muscles which depress scapula
106
Q

Middle trapezius role in upward rotation of the scapula

A

Retractor of the scapula

- synergist (cancels out protraction from serratus anterior)

107
Q

Lower trapezius role in upward rotation of the scapula

A
  • mover

- synergist (cancels out elevation from upper trapezius)

108
Q

Serratus anterior role in upward rotation of the scapula

A
  • mover

- synergist (cancels out retraction from middle trapezius)

109
Q

Function of the clavicle

A
  • acts as a strut (holds things further from the trunk)
    - holds the scapula laterally; increases ROM
    - part of pectoral girdle
110
Q

Shape of the clavicle

A

Curved (“crank like”) shape of clavicle increases shoulder region mobility
- medial is convex anteriorly, lateral is concave anteriorly

111
Q

Movements of clavicle

moving scap = movement of clavicle due to AC jt

A
  1. scap upward rotation = elevation of the clavicle (movement at the SC jt)
  2. tension in costoclavicular ligament ‘pushes’ the movement laterally (ensures clavicle doesnt elevate too far)
  3. some elevation at AC jt but next increasing tension in the conoid ligament ‘locks’ in posterior clavicle
  4. this (increasing tension in conoid ligament) causes posterior rotation of the clavicle (mvmt at both AC and SC joints)
  5. This completes the final elevation of the AC jt to achieve full ROM @ shoulder jt
112
Q

Implications of its “crank-like” shape for shoulder function

A
  • a small mvmt at the medial end of the clavicle
  • that movement is amplified into a bigger movement at the lateral end of the clavicle
  • because of the BENT shape –> dont need much movement medially to push lateral end of clavicle
  • the curved shape of the clavicle increases the arc of movement

ANAT102 (9 decks)

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