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DPT 702: Biomechanics > Lecture 9: arthrology of the shoulder Test 3 > Flashcards

Lecture 9: arthrology of the shoulder Test 3 Flashcards

1
Q

articulations of the shoulder complex

A

Sternoclavicula = clavicle strut holding scapula

Acromioclavicular = firmly attaches the scapula to clavicle

scapulothoracic = not a true joint; interface between bones; movements linked to AC/SC; position of scam provides base for GH

glenohumeral = most distal and mobile portion of complex

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2
Q

describe the shoulder complex

A

series of kinematic links

cooperate to maximize ROM

weakened/painful or unstable link decreases the effectiveness of entire UE

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3
Q

how does the scapula move with elevation/depression

A

superior and inferior glide respectively

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4
Q

how does the scapula move with protraction and retraction

A

medial border slides ant/lateral with protraction

retraction = posterior medial

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5
Q

how does the scapula move with upward rotation

A

inferior angle rotates superior lateral direction, glenoid fossa faces upward = UE elevation

downward rotation = inferior angle rotates inferior medial direction with UE lowering

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6
Q

what articulates at the SC joint

A

medial end of clavicle with clavicular facet on sternum

superior border of the cartilage of the 1st rib

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7
Q

what is the basilar joint of the UE

A

SC joint

links axial to appendicular skeleton

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8
Q

characteristics of SC joint

A

extensive periarticular tissues

irregular saddle shaped

convex and concave with sternal facet reciprocally shaped

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9
Q

where are the longitudinal diameters of the SC joint

A

extend roughly in the frontal plane between superior and inferior points of articular surfaces

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10
Q

what are the transverse diameters of the SC joints

A

extend roughly in the horizontal plane between anterior and posterior points of the articular surfaces

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11
Q

periarticular tissues of the SC joint (i.e what are the structures like muscles, ligaments, etc around the joint)

A

anterior and posterior SC ligaments (reinforce capsules)

interclavicualr ligament

costoclavicular ligament

articular disc (only 50% of people)

SCM, sternothyroid, sternohyoid, and subclavis muscles

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12
Q

movement at the SC joint

A

3 degrees of freedom (sagittal, frontal, and horizontal)

elevates/depresses, protracts/retracts, and rotates

goal = place scapula in optimal position for head of humerus

all movements of the GH joint involve some movement at SC

clavicle rotates in all 3 degrees of freedom with UE elevation

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13
Q

osteokinematics of elevation and depression of clavicle

A

generally parallel to frontal plane

axis is near anterior posterior

35-45 degrees elevation

10 degrees depression

clavicular motion produces similar in scapula

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14
Q

arthrokinematics of elevation and depression of the clavicle

A

occur along the longitudinal diameter

elevation = convex surface rolls superiorly and glides inferiorly; CC ligament stretches and limits motion

depression: convex surface rolls inferiorly and slides superiorly; intraclavicular ligament/superior portion of the capsule stretches

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15
Q

osteokinematics of protraction and retraction of the clavicle

A

occurs neatly parallel to horizontal plane

axis = vertical

15-30 degrees each direction

associated with scapular retraction/protraction

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16
Q

arthrokinematics of the clavicle with protraction and retraction

A

occurs along SC joints transverse diameter

retraction = concave surface of clavicle rolls and slides posteriorly on convex surface of sternum; stretches anterior CC ligament and anterior capsule

protraction = occurs in an anterior direction; stretches posterior CC ligament and posterior capsule, involved in reaching forward

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17
Q

osteokinematics of rotation of the clavicle

A

around the bones longitudinal axis

UE elevation: posterior rotation 20-35 degrees (point on superior clavicle)

as UE returns, clavicle returns

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18
Q

arthrokinematics of the clavicle with rotation

A

spin of its sternal end relative to the lateral surface of the articular disc

axial rotation is linked with the overall kinematics of flexion and abduction (can’t be performed with the arm resting at the side)

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19
Q

what are the articulations for the acromioclavicular joint

A

lateral end of clavicle and acromion of scapula

clavicular facet on the acromion faces medial and slightly superior

articular disc of varying form is present in most AC joints

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20
Q

periarticular tissues of the AC joint

A

capsule is directly reinforced by superior and inferior AC ligaments

coracoclavicular ligament (extrinsic stability for AC)

2 parts of coracoclavicualr ligament = trapezoid ligament and conoid ligament (go from the coracoid process to the clavicle)

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21
Q

describe the kinematics of the AC joint

A

subtle movements between scapula and lateral clavicle

optimizes mobility and fit between scapula and thorax

motions are described scapula relative to the clavicle

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22
Q

movements present at the AC joint

A

3degrees of freedom

up/downward rotation

secondary motions = rotational adjustment motions; to fine tune position of scapula (horz and sagittal plane)

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23
Q

describe upward rotation of the scapula at the AC joint

A

swings upward and out relative to the end of clavicle with upward rotation

natural motion as part of elevation

up to 30 degrees

contributes significantly to scapulothoracic motion

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24
Q

describe downward rotation of the scapula at the AC joint

A

scapula rotates around clavicle to return to anatomical position

it looks like frontal plane but really is is the scapular plane

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25
Q

what are rotational adjustment motions at the AC joint

A

pivoting or twisting type motions of the scapula around the lateral end of the clavicle

optimally align the scapula against the thorax

horizontal plane: vertical axis; medial border moves away (IR of glenoid fossa)

sagittal plane: medial-lateral axis; inferior angle pivots away (anterior tilt) or reverse (posterior tilt)

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26
Q

kinematics of AC joint with protraction

A

AC joint IR in the horizontal plane

helps align the anterior surcease of the scapula with the thorax curved surface

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27
Q

kinematics of AC with elevation of scapula

A

“shrugging” is accompanied by anterior tilt

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28
Q

what would happen if there were no scapular adjustments with movements

A

the scapula would have to follow the clavicle exactly and could not adjust to the thorax

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29
Q

describe the scapulothoracic joint

A

not a true joint: no direct contact, but separated by layers of muscles

scapula is seated between 2nd and 7th ribs; medial border 6 cm lateral to spine

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30
Q

motions of the scapulothoracic joint

A

large UE ROM largely dependent on scapular motion

10 degrees anterior tilt

5-10 degrees upward rotation

30-40 degrees internal rotation

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31
Q

muscles that separate the scapulothoracic joint

A

subscapularis

serratus anterior

erector spinae

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32
Q

describe elevation/depression at the scapulothoracic joint

A

composite SC and AC

scapulothoracic elevation is a summation of elevation at SC and downward RT at the AC joint

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33
Q

how can you describe protraction/retraction at the scapulothoracic joint

A

summation of horizontal motions at SC and AC

protracting the clavicle around SC joint; varies with the amount of IR

34
Q

describe upward/downward RT at the scapulothoracic joint

A

integral part of UE elevation

places the glenoid fossa in a position to support/stabilize the head of the humerus

summation of clavicular elevation and SC/scapular upward RT

full 60 degrees of upward RT

35
Q

describe the kinematics of scapulothoracic upward rotation

A

summation of elevation at the SC joint and upward RT at the AC joint

36
Q

general features of the glenohumeral joint

A

large convex head

shallow concavity = glenoid fossa

head positioned medially, superiorly, and posteriorly (normal retroversion)

37
Q

in anatomical position describe the inferior portion of the capsule of the shoulder

A

slackened

called axillary pouch

38
Q

what lines the inner wall of the GH joint

A

synovial membrane

39
Q

head of humerus and glenoid fossa are lined with

A

articular cartilage

40
Q

potential volume of space in GH joint

A

2x size of the humeral head

41
Q

primary stabilizers of GH joint

A

passive tension with embedded ligaments

active forces produced by local muscles (specifically rotator cuffs)

LHB crosses superiorly over the head of the humerus

42
Q

function of the capsular ligaments of the GH joint

A

limites extremes of RT and translation

help keep a negative intra-articualr pressure in GH joint

43
Q

describe the makeup of capsular ligaments

A

fibrous connective tissue

interlacing collagen fibers

thickening of capsule in complex bands

44
Q

function of superior capsular ligament

A

resists ER/inferior and anterior translations

45
Q

function of the middle capsular ligament

A

stabilizes most motions

especially restraint in 45-90 abduction and extremes of ER

slack in IR

blends with subscap

46
Q

function of the inferior band of capsular ligament

A

3 portions

taught in 90 degree abd

hammock like

supports the suspended humeral head

resists inferior/anterior-posterior translation

47
Q

what is the strongest portion of the capsule

A

anterior is the strongest/thickest portion of the capsule

primary ligamentous restraint to anterior translation (abd and neutral)

ABD and ER forceful dynamic activities are especially stressful

48
Q

coracohumeral ligament: where does it attach, when is it taught, what does it blend with, and what does it restrict

A

from the coracoid process to the greater tubercle

blends with the superior capsule and supraspinatus tendon

taut in anatomical position

restraint inferior translation and ER humeral head

49
Q

significance of the rotator cuffs

A

significant structural support to the capsule

blends with capsule

belly of muscles close to the joint

protects and acts as an active stabilizer

50
Q

4 rotator cuff muscles

A

subscapularis = thickest/anterior to capsule

supraspinatus, infraspinatus, and teres minor = posterior to the capsule

51
Q

regions of vulnerability for rotator cuff muscles

A

rotator interval: triangular space formed by the tendons of subscapularis and supraspinatus and the coracoid process

common site for dislocation

reinforced by LHB, coracohumeral ligament, and sup/mid capsular ligaments

52
Q

origin of the LHB

A

supraglenoid tubercle and labrum , intracapsular tendon crossed the humeral head, inter tubercle groove on anterior humerus

53
Q

LHB resists whats

A

restricts anterior translation of the humeral head

the force generated through the tendon across the dome of the humeral head resists anterior translation - needed in ABD

54
Q

describe the glenoid labrum

A

fibrocartilaginous ring

50% depth is from this structure

stabilizer

55
Q

tissues that reinforce/deepen the GH joint

A

joint capsule/GH ligaments

coracohumeral ligament

rotator cuff muscles

LHB

glenoid labrum

56
Q

describe the static stability of the GH joint

A

at rest the humerus is stable on the glenoid fossa

like a ball on an inclined surface

superior capsular structures (superior capsular ligament, CH ligament, and tendon of supraspinatus)

there is a resultant compressive force

57
Q

describe the forces of the rotator cuff and significance

A

RC has horizontal forces to help if there is a load added to the arm

muscular forces act as a rope that holds the scapula in position of the slightly upward fossa

disruption can cause humeral head to drift inferiorly due to plastic deformation of SCS = subluxation or dislocation

58
Q

what is the coracoacromial arch

A

formed by the coracoacromial ligament and acromion process

roof of the GH joint

creates subacromial space between the arch and the humeral head

average of 1 cm in adults with arm at rest by side

59
Q

what does the coracoacromial arch contain

A

supraspinatus muscle and tendon

subacromial bursa (direct extension of synovial membrane of the GH joint)

LHB

superior capsule

60
Q

where are the bursa of the GH joint

A

situated where significant frictionless forces develop such as between tendons, capsules and bones, muscles and ligaments, or 2 adj muscles

61
Q

what 2 bursa are superior to the humeral head

A

subacromial bursa (above SS) = protects SS from acromial bone

sub deltoid bursa = limitse friction forces between the deltoid and the SS tendon/humeral head

62
Q

kinematics of the GH joint

A

3 degrees of freedom

4th motion defined: horizontal abd/add (starts at 90 degrees abd - vertical axis)

anatomic position = 0 degrees

63
Q

describe abd/add of the GH joint

A

ABD:
rotation of humerus in frontal plane; AP axis

120 degrees NLs at GH joint

simultaneous 60 degrees upward scapular rotation

convex head of humerus rolls superiorly, slides inferiorly

larger head does not roll of due to this sliding

add is reverse

64
Q

describe dynamic stability of the GH joint

A

part of the SS tending blends with superior capsule

active contraction pulls the capsule tight and prevents it from being pinched between the humeral head and the undersurface of the acromion

at 90 deg ABD humeral head stretches ICL (axillary pouch) which acts like a hammock supporting the head of the humerus

65
Q

describe the height of the subacromial space and the significance

A

impacted bu GH arthrokinematics and scapular motion

critical minimum must be maintained for lack of compression of contents in the space:

7.5 mm at 20 deg ABD

2.6 mm at 85 deg ABD

5mm at 150 deg ABD

66
Q

clinical significance of the arch representing the subacromial space

A

arc is where SS potential compression is at 35-70 deg

67
Q

what is adhesive capsulitis

A

excessive thickening or stiffness in ICL

limits inferior slide of humeral head

superior roll leads to jamming of the humeral head against the coracoacromial arch

68
Q

what is impingement syndrome

A

unnatural and repeated compression/abrasion may damage the SS tendon, subacromial bursa, LHB tendon, or superior parts of the capsule

over time repeated compression may lead to this syndrome

69
Q

arthrokinematics of humerus with flex/ext

A

arthro = spinning motion of humeral head in fossa

70
Q

describe the surrounding structures of the GH joint with flexion and extension

A

most surrounding structures are taut

tension in posterior capsule may cause slight anterior translation of humerus in extremes of flexion

71
Q

how much range of flexion and extension is present in the shoulder with flexion and extension

A

120 degrees GH flexion/180 includes scapula

extension = 65 degrees active, 80 passive

72
Q

how does the scapula move with flexion and extension of the shoulder

A

slight anterior tilt of the scapula, stretch of capsular ligaments

73
Q

how does the humerus move with ER of the shoulder

A

axial rotation o the humerus in the horizontal plane

74
Q

ER/IR ROM present in shoulder

A

75-85 degrees IR

60-70 degrees ER

with ABD of 90 degrees, ER of up to 90 (variable)

neutral = in IR?

75
Q

roll/slide of humerus with ER

A

ER rolls posteriorly and slides anteriorly

reverse for IR

76
Q

describe the principle of scapulohumeral rhythm

A

natural coupling of GH ABD and Scapulothoracic Upward RT

after 30 degrees of ABD, rhythm is consistent

ratio = 2:1; for every 3 deg of ABD there are 2 deg at the GH joint and 1 deg at the ST upward RT

full arch of 180 degree movement = 120 at GH and 60 at ST

77
Q

describe the ST and SC joints during full abduction

A

60 degrees of movement at the ST joint is a combo of elevation at SC joint and upward RT at AC

SC joint elevates 30 deg during the 180 arch

78
Q

how does the clavicle move at the SC joint during ABD

A

clavicle retracts

starts at 20 deg posterior to the frontal plane

retracts another 15-20 degrees with ABD

79
Q

describe the tilt of the scapula with ABD and what these movements help with

A

as full abd occurs, the scapula tilts posteriorly and slightly rotates outward

at rest = anterior tilt of 10 degrees, IR 30-40 deg

with ABD it posteriorly tilts 20 deg

these movements help keep the scapula flush with the thorax, orients the fossa, and moves the coracoacromial arch away from the advancing humeral head

80
Q

describe the rotation of the clavicle with ABD

A

rotates posteriorly along its own axis

20-35 degrees during full ABD

those with subacromial impingement showed reduced RT

81
Q

describe the movement of the humerus with ABD

A

naturally ER with ABD

allows greater tubercle to pass posterior to the acromion

25-50 degree range; majority occurs before 70-80 degrees of ABD

DPT 702: Biomechanics (13 decks)

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