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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
Q

Elevation/Depression of Scapulothoracic Joint

A

Translatory frontal plane motion

SC and AC motion
Sc joint elevates and AC joints goes down to create elevation of joint

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26
Q

Protraction/Retraction of scapulothoracic

A

Translatory frontal plane motion

SC and SC rotations
clavicle protracts about SC joint
AC joint IR to offset the protraction

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27
Q

Upward Rotation of scapulothoracic

A

Rotational frontal plane motion

SC elevation and upward rotation of AC
produces upward rotation of scapula

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28
Q

Downward rotation of scapulothoracic

A

Rotational frontal plane motion

SC depression and SC downward rotation

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29
Q

Glenohumeral joint Arthrology

A

Capsule
Cartilage
Glenoid Labrum
Capsular Ligaments

30
Q

Capsule of GH joint

A

attaches along rim of glenoid fossa and extends to humeral neck
increases volume within capsule by 2x

31
Q

Glenoid labrum

A

makes up 50% of glenoid fossa
deepens concavity of joint, increasing contact area and providing stability

32
Q

Capsular ligaments

A

offer slight suction, puncturing capsule increasing passive mobility

Sup, Mid, Inf = glenohumeral ligament
Coracohumeral lig = blends with sup capsule

33
Q

All GH ligaments (sup, mid, inf) resist

A

ER and anterior translation

34
Q

Coracohumeral ligament resists

A

ER, inf translation

35
Q

Characteristics of GH joint

A

Ball and socket
3 degrees of freedom

36
Q

Flexion/Extension GH Joint

A

both directions spin

37
Q

Abduction/Adduction GH joint

A

convex on concave

Abduction: Roll –> Sup
Slide –> Inf

opposite for adduction

38
Q

Subacromial Space

A

Roll and slide necessary to avoid compression
supraspinatus helps to keep superior capsule taut and protects from impingement

39
Q

IR/ER GH joint

A

Convex on Cave
IR: roll–> anterior
Slide –> posterior

opposite for ER

40
Q

Horizontal Abduction/Adduction GH joint

A

convex on concave

adduction: roll–> anterior
slide–> posterior

opposite for horizontal abduction

41
Q

Principles of Shoulder Abduction

A

Scapulohumeral rhythm
scapular upward rotation
clavicle retraction
clavicle posterior rotation
scapular posterior tilt and ER
GH ER

42
Q

Scapulohumeral Rhythm

A

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
Q

Scapular upward rotation

A

combination of SC and AC joint motion
about equal of SC (elevation) and AC motion (upward rotation)

44
Q

Clavicle Retraction

A

retraction is greater during abduction in frontal plane vs abduction in scapular plane

45
Q

Clavicle Posterior Rotation

A

Clavicle rotates posteriorly during abduction
AC upward rotation stretches the coraclavicular ligament

46
Q

Scapular Posterior Tilt/ER

A

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
Q

Humeral ER allows…

A

allows greater tubercle to clear acromion during abduction

48
Q

Scapulothoracic Elevators

A

upper traps
levator scap
rhomboids

49
Q

Scapulothoracic Depressors

A

lower traps
pec minor
lats

50
Q

What muscle initiates abduction?

A

Deltoid

51
Q

What happens through 90° with abduction?

A

the supraspinatus contributes between 32% and 48% of submaximal torque

52
Q

What happens past 90° with abduction?

A

deltoid MA increases with abduction
supraspinatus MA decreases with abduction

53
Q

Movement of Upward Rotators

A

Serratus anterior has biggest moment arm, largest contributor
forces of muscles cause rotation w/o translation

54
Q

Middle Traps

A

Not a rotator, offsets protraction with retraction

55
Q

Serratus anterior and lower traps help to….

A

posterior tilt scapula

56
Q

Serratus anterior and middle traps help to…

A

externally rotate scapula

57
Q

Serratus anterior weak ess/paralysis

A

without this muscle, full shoulder abduction not possible
difficulty with upward rotation
results in downward rotation, anterior tilting, IR at scapula

58
Q

Scapular winging

A

flaring of medial border and inferior angle

59
Q

Rotator Cuff muscles

A

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
Q

GH internal rotators

A

subscap, pec major, lats, teres major, ant deltoid

stronger than external rotators

61
Q

GH ER

A

infraspinatus, teres minor, post deltoid

62
Q

GIRD

A

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
Q

Scapular dyskinesis

A

abnormal scapular movement–reduced upward rotation, increased IR, increased anterior tilt

SICK

64
Q

SICK

A

Scapular malposition
Inferior medial border prominence
Coracoid pain
Dyskinesis of movement

65
Q

Causes of SICK

A

no one cause
fatigue, weakness, injury, pain
chronically shortened pec minor and biceps

66
Q

Shoulder impingement

A

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
Q

Impingement might actually be…

A

tendinopathy of the supraspinatus or other rotator cuff muscles without impingement

68
Q

The scapula rests at what position?

A

IR
anterior tilt
upward rotation

69
Q

During shoulder abduction, scapula and clavicle motion in which direction help increase subacromial space?

A

posterior rotation

70
Q

The moment arm of IR/ER muscles decrease when placed in _______

A

90°abduction

2 Biomechanics (9 decks)

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