Topic 1: Bones and Joints of the Shoulder region Flashcards
1
Q
4 joints of the shoulder joint
A
- Glenohumeral joint
- AC joint (acroclavicular)
- Sternoclavicular joint
4.
2
Q
Classification of the Glenohumeral (shoulder) joint
A
Synovial, multiaxial, ball & socket
3
Q
Movements of the glenohumeral joint
A
- Flexion- extension (transverse axis)
- Abduction- adduction (anterioposterior axis)
- Internal (medial) - external (lateral) rotation (longitudinal axis)
4
Q
Articular surface of the glenohumeral joint
A
- Humeral head - 1/2 sphere (covered with articular cartilage to increase stability)
- glenoid fossa - very shallow
Only 25-30% contact between articular surfaces
5
Q
Glenohumeral jt fun fact
A
less stable than hip joint but more mobile
6
Q
Glenohumeral joint articular capsule
A
Very thin and lax –> aids mobility (enables more movements)
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
8
Q
Glenohumeral joint articular capsule reinforced by:
A
- rotator cuff tendons
- long head of triceps tendon
- glenohumeral and coracohumeral ligaments (capsular ligaments)
Helps stabilise the shoulder
9
Q
Glenohumeral joint articular capsule communicates with:
A
- subscapular bursa
2. intertubercular groove
10
Q
Glenohumeral joint synovial membrane
A
- lines joint capsule
- lines bony surfaces inside joint
capsule which are not covered by
articular cartilage
11
Q
Glenohumeral Joint- intra-articular structures
Glenoid Labrum
A
Fibrocartilaginous structure around glenoid fossa
12
Q
Glenoid Labrum functions
A
- facilitate mobility –> increases SA of jt
- increases glenoid concavity- up to 50%
- provides attachment site for joint capsule, ligaments, muscles
- deepens socket to increase stability
13
Q
Glenoid fossa bone bit fun fact
A
very small- needs other things to stabilise/ reinforce joint
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
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
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
17
Q
Glenohumeral ligaments
A
- From anterior glenoid rim to humerus (and capsular ligaments)
- inconsistent
1. superior 2. middle 3. Inferior
18
Q
Glenohumeral ligaments- SUPERIOR
A
- prevents lateral and therefore, inferior dislocation of the humerus
- limits external rotation (because its anterior)
19
Q
Glenohumeral ligaments- MIDDLE
A
Limits external rotation
20
Q
Glenohumeral ligaments - INFERIOR
A
- prevents anterior dislocation of humerus when fully flexed/ abducted
21
Q
Glenohumeral ligaments
TRANSVERSE HUMERAL
A
- passes between the humeral tubercles
2. holds long head of biceps brachii in the bicipital groove
22
Q
Scapulothoracic Movements
A
- elevation- depression
- Abduction- adduction
- upward rotation (glenoid fossa up)- downward rotation
- internal rotation- external rotation
- anterior tilt- posterior tilt
- protraction
- retraction
23
Q
Protraction combination movements
A
- abduction + internal rotation
e. g. squeeze arms forward
24
Q
Retraction combination movements
A
- adduction + external rotation
25
Sternoclavicular joint classification
Synovial, multiaxial, plane
| also called modified ball & socket
26
Sternoclavicular Joint articular surfaces
1. sternal end of clavicle (male)
2. clavicular notch of sternum (female)
3. costal cartilage of rib 1
27
Sternoclavicular Joint articular capsule
- strong
| - reinforced by capsular ligaments
28
Sternoclavicular Joint
2 separate synovial membranes
29
Sternoclavicular Joint- intra articular disc
1. assists in stability of SC joint
| - vertical disc dividing joint cavity into medial and lateral compartments
30
Sternoclavicular Joint- intra articular disc functions
1. shock absorber
2. prevents superior dislocation of clavicle
- thrusting forces
- weight in hand
31
Sternoclavicular Joint Ligaments
| COSTOCLAVICULAR LIGAMENT
- 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)
32
Sternoclavicular Joint Ligaments
| ANTERIOR STERNOCLAVICULAR LIGAMENT
(from sternum to clavicle)
| - limits retraction
33
Sternoclavicular Joint Ligaments
| POSTERIOR STERNOCLAVICULAR LIGAMENT
(from sternum to clavicle)
| - limits protraction
34
Sternoclavicular Joint Ligaments
| INTERCLAVICULAR LIGAMENT
(between clavicles)
| - limits clavicles popping up when downward force is applied
35
ACROMIOCLAVICULAR JOINT
| Classification
Synovial, multiaxial, plane
36
ACROMIOCLAVICULAR JOINT
| Articular Surfaces
- acromial end of clavicle
- anterior, medial acromion
between lateral end of clavicle and acromial process
37
ACROMIOCLAVICULAR JOINT
| Articular Capsule
- loose
- reinforced by capsular ligaments
- -> intra-articular disc (shock absorber)
- -----> partial disc which functions as a shock absorber
38
ACROMIOCLAVICULAR JOINT
| Ligaments -- Coraclavicular (CUNOID PART)
```
(from coracoid to clavicle)
Conoid part (attaches to conoid tubercle)
- vertical
- limits protraction of scapula
- produces axial rotation of clavicle
More medial
```
39
ACROMIOCLAVICULAR JOINT
| Ligaments -- Coraclavicular (TRAPEZOID PART)
```
(attaches to trapezoid line)
- oblique fibres
- limits retraction of scapula
- prevents medial dislocation of scapula
more lateral
```
40
Pectoral Girdle
1. scapula
2. clavicle
3. AC & SC joints
41
Pectoral girdle definition
Bone structure that attaches to the trunk
42
Glenoid fossa orientation
1. anterior (little bits)
2. lateral (lots)
3. superior (little)
part of the GH joint
43
Pectoral Girdle function
Increases the ROM for the shoulder joint
44
How does the pectoral girdle increase shoulder jt ROM?
1. By changing the position of the glenoid fossa
| 2. due to clavicle acting as a strut (holding shoulder away from trunk)
45
What happens to ROM if no girdle?
1. adbuction ROM drops from 180 to 120
| 2. flexion ROM drops form 180 to 120
46
Why does glenoid fossa position matter so much?
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
Stability of GH jt in pendant postn
Relies on passive structures (ligaments etc)
- orientation of fossa
- tension in ligaments and superior capsule
48
Stability of GH jt as it abducts
- orientation of fossa = ineffective
- needs dynamic stability (not passive)
- tension in ligaments and capsule reduced
49
Glenohumeral joint stability- GF orientation
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
Humeral head - GH stability (GF orientation)
- structures that prevent lateral movement of humeral head
| - prevent inferior movement of the humeral head --> increases stability
51
Structures that prevent lateral movement of humeral head
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
Functional significance of the position of GF in anatomical position
- 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
Shoulder joint classification
Synovial, multi-axial, ball and socket
54
Shoulder joint movements
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
Scapulathoracic joint classification
not an anatomical joint-- FUNCTIONAL JOINT
56
Scapula facts
- sits on thoracic cage
- has AC jt laterally
- otherwise, held in place by muscles "suspended by muscles"
57
Scapula movements
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
Scapulothoracic joint
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
Scapulothoracic joint contribution to full ROM for shoulder jt
1/3
60
What moves over the scapula?
muscles
61
Protraction of scapula
bring scaps forward -- arms out infront
62
retraction of scapula
squeezing something between shoulder blades - scaps go posterior
63
Upward & downward rotation of the scapula
lifting bent arms up & down
| - gleniod fossa faces up and down
64
Upward & downward rotation of scapula
| Point of reference
inferior angle of scap
65
Upward & downward rotation of scapula
| Point of interest
Glenoid Fossa
66
Scapula & clavicle movements
Relative positions of scapula & clavicle must be able to change
- occurs at AC joint
- small amounts of movement medially, larger amounts laterally
67
Clavicle movements in retraction
clavicle moves post
68
Clavicle movements in protraction
Clavicle moves anteriorly
69
Clavicle movements in elevation
Superiorly
70
Clavicle movements in depression
comes back to lower position
71
Contribution to movement by SC joint
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
where does the clavicle have more movement?
laterally
73
Scapulohumeral rhythm definition
Describes the movement relationship between the scapula and humerus
74
Scapulohumeral rhythm movements
Upward rotation of the scapula and abduction/ flexion of the humerus synchronously
75
Ratio of the "rhythm" of movements
2:1
GH: ST (scapulothoracic)
76
Scapulohumeral Rhythm total range of abduction:
180
77
Scapulohumeral Rhythm total range of abduction:
| ST joint contribution
1/3
| 60
78
Scapulohumeral Rhythm total range of abduction:
| GH joint:
2/3
| 120
79
"Rhythm" refers to:
1. quality of movement
2. equal R v L of patient
3. how coordinated the movement it is
80
Scapulohumeral rhythm initial scapula movement
little/ no movement in the first 30 degrees abduction
| no change in inferior angle
81
SH rhythm sequence:
1. GH all time
2. SC jt
3. AC jt to continue to full ROM
82
What is the SC joint motion associated with to do with the clavicle
Clavicular elevation
| - costoclavicular (medial & inferior) ligament limits this
83
What is the AC joint motion associated with to do with the clavicle
Rotation
| - clavicle moves backward in abd --> rotated posteriorly
84
Where are the SC & AC movements realised?
ST (scapulothoracic) joint
*realised = sum of movements & see movements
85
What does scapulohumeral rhythm do?
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
What is optimal length?
Sarcomeres = just right length for contraction (length-tension relo from sem 1)
87
Length tension relationship defintion
Direct relationship between the tension a muscle fibre can produce and the length of sarcomeres in the muscles
88
Rotator Cuff muscles function
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
Anatomical actions of the Rotator cuff muscles
1 abductor (supraspinatus), 1 internal rotator (subscapularis), 2 external rotators (teres minor & infraspinatus)
90
Rotator cuff muscles
1. supraspinatus
2. infraspinatus
3. teres minor
4. subscapularis
91
Rotator cuff muscles synergist function
- 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
Desired movement of the RC muscles
ABDUCTION
93
Function of the deltoid muscle in RC
mover
94
What happens when the deltoid contracts in abduction?
Humeral head will glide superiorly --> we want it in the centre (turns on its stabiliser function)
95
Synergists in rotator cuff muscles
inferior part of subscapularis cancels out rotations
inferior part of infrapsinatus cancels out rotations
teres minor - prevents superior glide of humeral head
96
Function of scapular muscle e.g. upward rotation of the scapula
what does upward rotation accompany?
- abduction &/or flexion of the shoulder joint -- needs Scap
97
What does upward rotation of the scapula do to the glenoid fossa?
Moves the GF; thus, increasing the mobility of the shoulder
| - head of humerus still has space to move on glenoid fossa
98
Upward rotation of the scapula RC muscles relo
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
Muscles which contract to produce upward rotation of the scapula
Trapezius & serratus anterior
100
Serratus anterior actions
Protract & upwardly rotate scapula
101
Upper trapezius actions
Elevate & upwardly rotate scapula
102
Middle trapezius actions
retract scapula
103
Lower trapezius actions
Depress & upwardly rotate scapula
| - attachment to scap = close to superior angle; therefore, contraction = angular drop = upward rotation
104
Serratus anterior location
Attaches on the medial border of scapula & runs superficial to subscapularis --> attaches anteriorly onto ribs
105
Upper trapezius role in upward rotation of the scapula
- 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
Middle trapezius role in upward rotation of the scapula
Retractor of the scapula
| - synergist (cancels out protraction from serratus anterior)
107
Lower trapezius role in upward rotation of the scapula
- mover
| - synergist (cancels out elevation from upper trapezius)
108
Serratus anterior role in upward rotation of the scapula
- mover
| - synergist (cancels out retraction from middle trapezius)
109
Function of the clavicle
- acts as a strut (holds things further from the trunk)
- holds the scapula laterally; increases ROM
- part of pectoral girdle
110
Shape of the clavicle
Curved ("crank like") shape of clavicle increases shoulder region mobility
- medial is convex anteriorly, lateral is concave anteriorly
111
Movements of clavicle
| moving scap = movement of clavicle due to AC jt
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
Implications of its "crank-like" shape for shoulder function
- 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
