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2 Biomechanics > Shoulder > Flashcards

Shoulder Flashcards

1
Q

Joints of shoulder

A

sternoclavicular
acromioclavicular
scapulotharoacic
glenohumeral

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2
Q

Shoulder joint is equivalent to…

A

glenohumeral

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3
Q

Shoulder movement is equivalent to….

A

all 4 joints

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4
Q

Articulations of clavicle

A

sternal facet to clavicular facet of sternum
costal facet to first rib
acromial facet to clavicular facet of acromion

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5
Q

Angle of inclination

A

frontal plane angle between humeral neck/head and humeral shaft
normal angle is 135°

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6
Q

Humeral torsion

A

Transverse plane angle between medial/lateral axis (elbow) and the humeral neck/head

normal angles range from 30° posterior to medial/lateral axis

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7
Q

Humeral torsion at birth

A

65°
de rotates due to mechanical stress on the arm

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8
Q

Mechanical Stress During Youth

A

torsional stress in youth pitchers either causes greater retroversion or inhibits natural retroversion reduction

Elite pitchers demonstrate 10-15°retroversion in pitching arm

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9
Q

Why is the sternoclavicular joint important?

A

Major link between the upper extremity and axial skeleton
must have firm attachment yet allow for considerable range of motion
incredibly STABLE joint, large forces through joint cause fracture before dislocation

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10
Q

Joint characteristics of sternoclavicular

A

SADDLE
3 degrees of freedom

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11
Q

Articular disc of sternoclavicular

A

fully formed in 50% of humans
separates joint into 2 cavities
strengthens the articulation and acts as shock absorber

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12
Q

Superior/Inferior surfaces of sternoclavicular

A

Clavicle: convex
Sternum: concave

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13
Q

Anterior/posterior surfaces of sternoclavicular

A

Clavicle: concave
Sternum: Convex

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14
Q

Depression/Elevation of sternoclavicular

A

Elevation: Clavicle on sternum, vex on cave
Roll–> superior
Slide–> inferior

opposite for depression

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15
Q

Limiting ligament for elevation SC

A

costoclavicular ligament

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16
Q

Limiting ligaments for depression SC

A

interclavicular
sternoclavicular (superior)

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17
Q

Protraction/Retraction SC joint

A

Cave on vex
Protraction: roll and slide are both anterior.

opposite for retraction

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18
Q

Protraction limiting ligaments SC joint

A

posterior costoclavicular
posterior sternoclavicular

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19
Q

Retraction limiting ligaments SC joint

A

anterior costoclavicular
anterior sternoclavicular

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20
Q

Anterior/Posterior Rotation of SC joint

A

Convex on concave does not apply
spin in both directions, does not occur in rest, but in 20-25 degrees of abduction/flexion

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21
Q

Articular discs of AC joint

A

fully formed in 10% of cadavers
likely indicates degenration, not structural anomaly

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22
Q

Joint characteristics of AC joint

A

PLANE
3 degrees of freedom (1 primary, 2 readjustments)

Sagittal & Transverse = secondary/readjustments
Frontal = primary

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23
Q

Scapulothoracic Joint

A

Not a true joint
Scapula is inbetween 2nd and 7th ribs

resting position is 10 degrees anterior tilt, 5-19 degrees of upward rotation, 30-40 degrees of IR

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24
Q

Scapulothoracic Joint Characteristics

A

Not a joint
3 degrees of freedom
2 are readjustments, 1 is primary (frontal)

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25
Elevation/Depression of Scapulothoracic Joint
Translatory frontal plane motion SC and AC motion Sc joint elevates and AC joints goes down to create elevation of joint
26
Protraction/Retraction of scapulothoracic
Translatory frontal plane motion SC and SC rotations clavicle protracts about SC joint AC joint IR to offset the protraction
27
Upward Rotation of scapulothoracic
Rotational frontal plane motion SC elevation and upward rotation of AC produces upward rotation of scapula
28
Downward rotation of scapulothoracic
Rotational frontal plane motion SC depression and SC downward rotation
29
Glenohumeral joint Arthrology
Capsule Cartilage Glenoid Labrum Capsular Ligaments
30
Capsule of GH joint
attaches along rim of glenoid fossa and extends to humeral neck increases volume within capsule by 2x
31
Glenoid labrum
makes up 50% of glenoid fossa deepens concavity of joint, increasing contact area and providing stability
32
Capsular ligaments
offer slight suction, puncturing capsule increasing passive mobility Sup, Mid, Inf = glenohumeral ligament Coracohumeral lig = blends with sup capsule
33
All GH ligaments (sup, mid, inf) resist
ER and anterior translation
34
Coracohumeral ligament resists
ER, inf translation
35
Characteristics of GH joint
Ball and socket 3 degrees of freedom
36
Flexion/Extension GH Joint
both directions spin
37
Abduction/Adduction GH joint
convex on concave Abduction: Roll --> Sup Slide --> Inf opposite for adduction
38
Subacromial Space
Roll and slide necessary to avoid compression supraspinatus helps to keep superior capsule taut and protects from impingement
39
IR/ER GH joint
Convex on Cave IR: roll--> anterior Slide --> posterior opposite for ER
40
Horizontal Abduction/Adduction GH joint
convex on concave adduction: roll--> anterior slide--> posterior opposite for horizontal abduction
41
Principles of Shoulder Abduction
Scapulohumeral rhythm scapular upward rotation clavicle retraction clavicle posterior rotation scapular posterior tilt and ER GH ER
42
Scapulohumeral Rhythm
There is 2 to 1 ratio of GH abduction to scapular upward rotation during abduction 180° total, 120 of GH and 60 of scapular upward rotation
43
Scapular upward rotation
combination of SC and AC joint motion about equal of SC (elevation) and AC motion (upward rotation)
44
Clavicle Retraction
retraction is greater during abduction in frontal plane vs abduction in scapular plane
45
Clavicle Posterior Rotation
Clavicle rotates posteriorly during abduction AC upward rotation stretches the coraclavicular ligament
46
Scapular Posterior Tilt/ER
Scapula is naturally internally rotated. Abduction causes slight scapula ER Scapula is anteriorly rotated at rest, during abduction, it will posteriorly rotate these actions increase subacromial space
47
Humeral ER allows...
allows greater tubercle to clear acromion during abduction
48
Scapulothoracic Elevators
upper traps levator scap rhomboids
49
Scapulothoracic Depressors
lower traps pec minor lats
50
What muscle initiates abduction?
Deltoid
51
What happens through 90° with abduction?
the supraspinatus contributes between 32% and 48% of submaximal torque
52
What happens past 90° with abduction?
deltoid MA increases with abduction supraspinatus MA decreases with abduction
53
Movement of Upward Rotators
Serratus anterior has biggest moment arm, largest contributor forces of muscles cause rotation w/o translation
54
Middle Traps
Not a rotator, offsets protraction with retraction
55
Serratus anterior and lower traps help to....
posterior tilt scapula
56
Serratus anterior and middle traps help to...
externally rotate scapula
57
Serratus anterior weak ess/paralysis
without this muscle, full shoulder abduction not possible difficulty with upward rotation results in downward rotation, anterior tilting, IR at scapula
58
Scapular winging
flaring of medial border and inferior angle
59
Rotator Cuff muscles
excel at providing dynamic stability rotate humeral head compress humeral head in glenoid fossa all active during adduction and extension supraspinatus = superior roll rest of muscles = inferior slide
60
GH internal rotators
subscap, pec major, lats, teres major, ant deltoid stronger than external rotators
61
GH ER
infraspinatus, teres minor, post deltoid
62
GIRD
deficit in IR pitchers have greater retroversion on throwing side allows for greater ER ROM but IR is less other factors: less IR to absorb forces, posterior capsule thickness, humeral head moves anteriorly, anterior capsule loosens
63
Scapular dyskinesis
abnormal scapular movement--reduced upward rotation, increased IR, increased anterior tilt SICK
64
SICK
Scapular malposition Inferior medial border prominence Coracoid pain Dyskinesis of movement
65
Causes of SICK
no one cause fatigue, weakness, injury, pain chronically shortened pec minor and biceps
66
Shoulder impingement
repeated overhead movements with narrowed subacromial space can irritate supra tendon, biceps, bursa could be caused by adhesive capsulitis, which causes damage to supra tendon, bursa, and biceps
67
Impingement might actually be...
tendinopathy of the supraspinatus or other rotator cuff muscles without impingement
68
The scapula rests at what position?
IR anterior tilt upward rotation
69
During shoulder abduction, scapula and clavicle motion in which direction help increase subacromial space?
posterior rotation
70
The moment arm of IR/ER muscles decrease when placed in _______
90° abduction

2 Biomechanics (9 decks)

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