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Biomechanics IV > Exam 3 lecture: shoulder > Flashcards

Exam 3 lecture: shoulder Flashcards

1
Q

what is scapulohumeral rhythm?

A

arm trunk mechanism

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2
Q

what are the 4 important joints of the shoulder complex?

A

scapulocostal
sternoclavicular
acromioclavicular
glenohumeral

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3
Q

what type of joint is the glenohumeral joint?

A

ball and socket / enarthrosis

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4
Q

what is the effect of the depth of the glenoid fossa on stabilty?

A

the glenoid fossa is shallow –> less static stability

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5
Q

t or f: the head of the humerus is larger than the glenoid fossa.

A

true

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6
Q

what is the significance of the glenoid fossa being anteverted?

A

there is little anterior stability

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7
Q

what happens if the glenoid fossa is retroverted?

A

there would be less posterior stability

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8
Q

what increases the glenohumeral socket depth and size?

A

the labrum

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9
Q

what is the labrum made of?

A

fibrocartilage

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10
Q

t or f: the labrum completely encircles the glenoid fossa (i.e. makes a complete O shape)

A

true

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11
Q

what is a Bankart lesion?

A

anterior detachment of the joint capsule from the labrum

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12
Q

what is a SLAP lesion?

A

superior labrum anterior posterior;
commonly seen in throwing athletes;
biceps or cuff msl detaches from superior labrum

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13
Q

what are common causes of labral damage?

A

dislocation, increased mobility, overuse

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14
Q

what is the shape of the humeral head?

A

1/3 of a sphere

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15
Q

what is the position of the humeral head? (i.e. anteverted vs. retroverted)

A

retroverted (b/c the glenoid fossa is anteverted)

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16
Q

what is the effect of the humeral head being retroverted?

A

there is less resistance to anterior translation, and more resistance to posterior translation

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17
Q

what attaches to the greater and lesser tubercles?

A

rotator cuff msls

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18
Q

what attaches to the intertubercular sulcus?

A

biceps long head, transverse lig, subscapularis and pectoralis msls

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19
Q

in which directions is the glenohumeral joint strong?

A

anterior and inferior

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20
Q

in which directions is the glenohumeral joint weak?

A

posterior (no posterior ligs)

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21
Q

what are the 4 ligaments of the glenohumeral joint in order of importance?

A

inferior GH lig
middle GH lig
super GH lig
coracohumeral lig

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22
Q

which glenohumeral ligament is the strongest?

A

inferior GH lig

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23
Q

which glenohumeral ligament is the most injured?

A

inferior GH lig

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24
Q

what are the two parts of the inferior GH lig?

A

anterior and posterior

25
Q

what is the function of the coracohumeral lig?

A

resist distraction and inferior translation w/arm at side

26
Q

what is the function of the superior GH lig?

A

main resistor of distraction, external rotation, and adduction of arm w/arm at side

27
Q

what is the function of the middle GH lig?

A

resist distraction and external rotation w/arm abducted 45-60˚

28
Q

what is the function of the inferior GH lig?

A

most important lig w/arm abducted >90˚; folds like an accordion

29
Q

what happens to the GH joint capsule when the arm is dependent?

A

lax/folded capsule

30
Q

what happens to the GH joint capsule when the arm is abducted?

A

taught/unfolded capsule

31
Q

what is resting position of the arm?

A

dependent position = hanging at side, 0˚

32
Q

what is tight packed position of the arm?

A

abducted and externally rotated

33
Q

what are static stabilizers of the glenohumeral joint?

A

capsule/ligs - IGHL most important

labrum

34
Q

what are the dynamic stabilizers of the glenohumeral joint?

A

rotator cuff, esp. w/arm abducted, biceps, trices, pec minor

35
Q

when is the GH jt most vulnerable to dislocation?

A

abduction and external rotation / FOOSH

36
Q

which direction are most dislocations?

A

anterior

37
Q

what is the suprahumeral joint?

A

between the coracoacromial arch and the humeral head

38
Q

what are the contents of the suprahumeral joint?

A

subacromial bursa
rotator cuff tendon (esp. supraspinatus)
biceps brachii long head

39
Q

what are the 3 parts of the coracoacromial arch?

A

coracoid, acromion, coracoacromial lig.

40
Q

what muscles and actions decrease risk of impingement at the suprahumeral joint?

A

external rotation
inferior translation
cuff and biceps

41
Q

what muscles and actions increase risk of impingement at the suprahumeral joint?

A 
internal rotation
superior translation
deltoid, internal rotators, triceps (long head), pectoralis minor
kyphosis
shoulder hiking
42
Q

what is the progression of the acromioclavicular joint as you age?

A

fibrocartilaginous symphysis @ birth
2 cavities w/fibrocartilaginous disc @ 3-4 yrs
meniscus @ 20 yrs
degenerated by 20-30 yrs, not always symptomatic

43
Q

what is a common site for shoulder separation?

A

acromioclavicular joint

44
Q

what are the extracapsular ligs of the acromioclavicular joint

A

coracoclavicular ligs (conoid, trapezoid) - most important stabilizers

45
Q

what forces do the coracoclavicular ligs resist?

A

distractive forces

46
Q

what causes distraction at the AC joint?

A 
abduction & horizontal abduction
flexion
external rotation
lifting (i.e. suitcase)
pull up or chin up
47
Q

what causes compression at the AC joint?

A

adduction
horizontal abduction
pushing
pushup

48
Q

why can dislocation of the sternoclavicular joint be lethal?

A

b/c it can block the airway

49
Q

what are the supportive muscles of the SC joint?

A

pectoralis major, trapezius, SCM, subclavius

50
Q

what is the role of subclavius?

A

extensile/contractile lig to add stability to proximal end

51
Q

why is the interclavicular ligament so unique?

A

b/c it supports both R and L SC joints.

52
Q

what is the most important ligament of the sternoclavicular lig?

A

costoclavicular lig

53
Q

what does the costoclavicular lig resist?

A

anterior: distraction, depression, elevation, external rotation of clavicle @ SC jt.
posterior: compression, depression, elevation, internal rotation @ SC jt

54
Q

why is the clavicle important?

A

connects the upper limb to the axial skeleton

55
Q

t or f: the clavicle moves with the scapula.

A

false. the clavicle moves similarly to the humerus

56
Q

what is the significance of the clavicle moving similarly to the humerus?

A

less torsion/bending

57
Q

what are the 3 phases of scapulohumeral rhythm?

A

phase 1 = 0-30˚
phase 2 = 30˚-90˚
phase 3 = 90˚ - 180

58
Q

what are the motions to watch during scapulohumeral rhythm

A

humerus @ GH (accounds for 120˚ total)
scapula (60˚ external rotation)
clavicle @ SC (results in 60˚ distal elevation)
acromion @ SC (20˚ total rotation w/distal clavicle

59
Q

how much of the motion of the shoulder joint is in the GH jt?

A

2/3

Biomechanics IV (5 decks)

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