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Biomechanics Winter 2024 > Shoulder Study guide > Flashcards

Shoulder Study guide Flashcards

1
Q

What type of joint is the sternoclavicular joint?

A
  • saddle joint
  • clavicle: Convex longitudinally, concave transverse
  • sternum: convex transverse, concave longitudinally
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2
Q

How many degrees of freedom does the SCJ have?

A

3
- protraction/retraction (transverse plane)
- elevation/depression (frontal plane)
- axial rotation (sagittal plane)

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3
Q

What osteokinematic motions of the arm are associated with each movement of the SCJ?

A

-protraction/retraction
- elevation/depression
- axial rotation

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4
Q

Describe the arthrokinematics of the clavicle during protraction

A

clavicle concave
- rolls and slides anterior

Ant. SC ligament: slack
Post. SC ligament: taut

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5
Q

Describe the arthrokinematics of the clavicle during retraction

A

clavicle concave
- rolls and slides posterior

Ant. SC ligament: taut
Post. SC ligament: slack
costoclavicular ligament: taut

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6
Q

Describe the arthrokinematics of the clavicle during elevation

A

clavicle convex
- rolls superior
- slides inferior

costoclavicular: taut
interclavicular: slack

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7
Q

Describe the arthrokinematics of the clavicle during depression

A

clavicle convex
- rolls inferior
- slides superior

costoclavicular: slack
interclavicular: taut

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8
Q

Which ligaments restrict elevation of the SCJ

A
  • Ant./Post. SC ligaments
  • Interclavicular
  • Costoclavicular
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9
Q

Which ligaments restrict depression of the SCJ

A
  • Interclavicular ligament
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10
Q

Which ligaments restrict retraction of the SCJ

A
  • Ant./post. SC ligament
  • Interclavicular ligament
  • Costoclavicular ligament
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11
Q

What type of joint is the acromioclavicular joint?

A
  • gliding/plane joint

follows same movements as scapular motions

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12
Q

What ligaments are associated with the ACJ & what do they do?

A

Coracoclavicular (conoid & trapezoid)
- suspends the clavicle from the arm

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13
Q

How many degrees of freedom does the ACJ have and what are the planes?

A

3 degrees of freedom
- upward/downward rotation (frontal plane)
- IR/ER (transverse plane)
- Anterior/posterior tilting (sagittal plane)

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14
Q

What osteokinematic motions are associated with the movement of the ACJ?

A
  • Upward rot: abduction or flexion
  • downward rot: adduction or ext from flexion
  • IR: protraction of ST joint
  • Ant tilt: elevation of ST joint
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15
Q

What is the scapulothoracic joint?

A
  • not actually a joint
  • the articulation between the thoracic cage and scapula
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16
Q

What is scaption?

A
  • elevation of the arm within the scapular plane
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16
Q

What is meant by the plane of the scapula?

A

The resting position of the scapula
- 10 degrees anterior tilt
- 5-10 degrees upward rotation
- 30-40 degrees internal rotation

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17
Q

What occurs at the SCJ & ACJ during scapular elevation

A

SCJ: clavicle elevation
ACJ: downward rotation

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17
Q

What occurs at the SCJ & ACJ during scapular depression

A

SCJ: clavicle depression
ACJ: upward rotation

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18
Q

What occurs at the SCJ & ACJ during scapular protraction

A

SCJ: clavicle protraction
ACJ: AC IR

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19
Q

What occurs at the SCJ & ACJ during scapular retraction

A

SCJ: clavicle retraction
ACJ: AC ER

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20
Q

What occurs at the SCJ & ACJ during scapular upward rotation

A

SCJ: clavicle elevation
ACJ: AC upward rotation

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21
Q

What occurs at the SCJ & ACJ during scapular downward rotation

A

SCJ: clavicle depression
ACJ: AC downward rotation

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22
Q

Which muscles control elevation of the scapula?

A
  • upper trap
  • levator scapulae
  • rhomboids
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23
Q

Which muscles control depression of the scapula?

A
  • lower trap
  • lats
  • pec minor
  • subclavius
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24
Q

Which muscles control protraction of the scapula?

A
  • serratus anterior
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25
Q

Which muscles control retraction of the scapula?

A
  • middle trap
  • lower trap
  • rhomboids
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26
Q

Which muscles control upward rotation of the scapula?

A
  • serratus anterior
  • upper trap
  • lower trap
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27
Q

Which muscles control downward rotation of the scapula?

A
  • levator scapula
  • rhomboids
  • pec minor
  • lats
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28
Q

Which muscles control posterior tilting of the scapula?

A
  • lower trap
  • serratus anterior
  • middle trap
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29
Q

Which muscles control external rotation of the scapula?

A
  • middle trap
  • serratus anterior
  • lower trap
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30
Q

What type of joint is the GHJ?

A
  • ball in socket joint
31
Q

How many degrees of freedom does the GHJ have?

A

3 degrees
- ER/IR: transverse plane
- Abd/add: frontal plane
- Flex/ext: sagittal plane

*4th motion: horizontal abd/add - vertical AoR

32
Q

What are the arthrokinematics of the humerus during flex/ext

A

pure spin

33
Q

What are the arthrokinematics of the humerus during abduction

A

humeral head:
- rolls superior
- slides inferior

34
Q

What are the arthrokinematics of the humerus during adduction

A

humeral head:
- rolls inferior
- slides superior

35
Q

What are the arthrokinematics of the humerus during external rotation

A

humeral head:
- rolls posterior
- slides anterior

36
Q

What are the arthrokinematics of the humerus during internal rotation

A

humeral head:
- rolls anterior
- slides posterior

37
Q

Name the capsular ligaments of the GHJ

A
  • superior glenohumeral
  • middle glenohumeral
  • inferior glenohumeral
  • coracohumeral
38
Q

What does the superior GH ligament resist?

A

ER and inferior/anterior translation

taut in anatomical neutral

39
Q

What does the middle GH ligament resist?

A

anterior translation

taut in 45-90 degrees abduction

40
Q

What does the inferior GH ligament resist?

A

Anterior band (strongest):
- anterior translation
taut in 90 abd & ER

Posterior band:
taut in 90 degrees abd & IR

Axillary pouch:
- inferior translation
taut in 90 degrees abd

41
Q

What does the coracohumeral ligament resist?

A

inferior translation & ER
taut in anatomical neutral

42
Q

What are the static stabilizers of the GHJ?

A

Non-contractile
- capsular ligaments
- glenoid labrum

43
Q

What are the dynamic stabilizers of the GHJ?

A

contractile tissue
- rotator cuff
- biceps LH

44
Q

What is dynamic centralization?

A
  • the contractile & passive tension keeping GHJ congruency
  • infraspinatus limits capsular slack/stabilizes anterior slide of humeral head
  • passive tension of subscapularis, middle GH ligament, and coracohumeral ligament balances posterior forces
45
Q

What is the rotator cuff interval?

A
  • anterior/superior part of the capsule that rotator cuff does not cover/blend

common site for anterior dislocations

46
Q

Which muscles are responsible for flexion of the GHJ?

A
  • anterior deltoid
  • coracobrachialis
  • biceps brachii
47
Q

Which muscles are responsible for extension of the GHJ?

A
  • posterior deltoid
  • lats
  • teres major
  • triceps LH
  • pec major (sternocostal head)
48
Q

Which muscles are responsible for abduction of the GHJ?

A
  • middle deltoid
  • supraspinatus
  • anterior deltoid
49
Q

Which muscles are responsible for external rotation of the GHJ?

A
  • infraspinatus
  • teres minor
  • posterior deltoid
50
Q

Which muscles are responsible for internal rotation of the GHJ?

A
  • subscapularis
  • pec major
  • lats
  • teres major
  • anterior deltoid
51
Q

What are the consequences on the GHJ of a downwardly rotated scapular position?

A
  • decreased compressive forces
  • increased risk for subluxation/dislocation inferiorly
  • plastic deformation of SCS
52
Q

What are the consequences on the subacromial space of a downwardly rotated scapular position?

A
  • increased compression of the subacromial space
  • pain
  • limited ROM
53
Q

What structures live in the subacromial space?

A
  • supraspinatus tendon
  • subacromial bursa
  • biceps LH tendon
  • superior capsule
54
Q

What effect will a tight posterior capsule of the GHJ have on the humeral head during elevation?

A
  • can displace humeral head too far anteriorly
  • leads to subacromial impingement syndrome
55
Q

What are the 6 principles needed for proper arm abduction kinematics?

A

1) scapulohumeral rhythm
2) SC elevation & AC upward rotation
3) clavicle retracts at SCJ
4) scapula posteriorly tilts & ER’s
5) clavicle posteriorly rotates
6) GHJ ER’s

56
Q

What is scapulohumeral rhythm?

A
  • scapula and humerus move together in order to perform full ROM
  • 2:1 ratio (2 degrees GHJ; 1 degree STJ)

AFTER 30 degrees abduction:
- every 3 degrees of movement comes from 2 degrees of GHJ and 1 degree of STJ

57
Q

What compensation during shoulder abduction might you see if the rotator cuff is not working properly and the upper trap is overactive?

A
  • shoulder shrugging
  • upper trap stronger than rotator cuff
  • trap-serratus imbalance
58
Q

Explain the force couple for scapular upward rotation

A
  • serratus anterior pulls inferior angle anterior
  • upper trap elevates GHJ
  • lower trap depresses medial boarder
59
Q

Explain the force couple for glenohumeral abduction

A
  • supraspinatus rolls humeral head
  • deltoids translate

inferior slide from:
- subscapularis
- infraspinatus
- teres minor
- passive lats/teres major

60
Q

Explain the consequences of a habitual rounded shoulders posture

A
  • depressed, downwardly rotated, protracted, slight IR, anterior tilted scapula
  • increased risk of subacromial impingement
  • could lead to elevated clavicle @ SCJ & depressed ACJ
61
Q

What is scapular dyskinesis?

A
  • paralysis/weakness of trapezius & serratus anterior (& middle trap)
  • no upward rotation w/ abduction
62
Q

What are the effects on scapulothoracic and glenohumeral joint kinematics with scapular dyskinesis?

A
  • scapula downwardly rotated w/ resisted elevation
  • winging scapula due to ineffective serratus anterior (doesn’t maintain congruency w/ thoracic cage)
  • snapping scapula
  • abnormal position of scapula: reduced upward rotation, excessive downward rotation, IR, anterior tilt, or elevation
63
Q

Explain scapular diakinesis’s effect on regions near the shoulder girdle

A
  • pec minor will shorten overtime
  • thoracic kyphosis
  • subacromial impingement
64
Q

Explain scapular dyskinesis’s effect on other structures that live in the shoulder girdle

A
  • deltoid & supraspinatus shorten leading to ineffective length-tension relationship
  • can reduce volume in subacromial space
  • serratus anterior paralysis
  • GHJ ligament & muscle abnormalities
  • RTC degeneration
65
Q

Why would once chose to strengthen the shoulder in the scapular plane rather than pure abduction?

A
  • more natural compared to pure abduction
  • more room to move w/o ER of shoulder
  • greater tubercle under high point of acromion
  • allows humeral head to be oriented more directly into glenoid fossa
66
Q

What is subacromial impingement syndrome?

A
  • reduced inferior slide leads to humerus jamming into subacromial structures in subacromial space
  • reduced volume within subacromial space
67
Q

What pathologies can arise from repetitive overhead throwing and why?

A
  • subacromial impingement
  • RTC syndrome
  • Ball-throwers fracture (spiral fracture in distal 3rds of the humerus)
  • little league shoulder (epiphysis becomes fractured or displaced)
  • tears/degeneration w/ ER
68
Q

What is shoulder instability?

A
  • excessive laxity associated with pain, apprehension, or lack of function
  • most common anterior and inferior
69
Q

What are some causes of shoulder instability?

A
  • Glenohumeral internal rotation deficit (GIRD)
  • RTC syndrome
70
Q

What is the difference between a slap tear and a bankart tear?

A

SLAP:
- superior labrum anterior to posterior
- biceps LH “peel-back” mechanism at end range of ER
- 90 degree abduction & endrange ER

Bankart tear:
- anterior-inferior rim of glenoid
- leads to instability

71
Q

How would hypomobility at the GHJ affect the SCJ and ACJ?

A
  • total humeral ROM reduced
  • can combine w/ STJ to improve ROM
  • lead to scapular substitution
72
Q

How would hypomobility at the SCJ affect the GHJ and ACJ?

A
  • decreased clavicular elevation, rotation, retraction, and scapular upward rotation
  • increased scapular IR
  • elevation dependent on GHJ
  • limited ACJ upward rotation because decreased clavicular posterior rotation
73
Q

How would hypomobility at the ACJ affect the SCJ and GHJ?

A

(usually HYPERmobility)
- scapular motion limited
- SCJ motion limited due to clavicular connection to ACJ
- Clavicular protraction brings scapula into thorax

74
Q

What are the AAOS norms for shoulder flexion/extension?

A

Flexion:
- 180

Ext:
- 60

75
Q

What are the AAOS norms for shoulder abduction/adduction?

A

Abduction:
- 180

Adduction:
- 0

76
Q

What are the AAOS norms for shoulder IR/ER?

A

IR:
- 70

ER:
- 90

Biomechanics Winter 2024 (6 decks)

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