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Biomechanics Exam 3 > Shoulder Arthrology > Flashcards

Shoulder Arthrology Flashcards

1
Q

Which joint is made up of the clavicle acting like a strut holding the scapula?

A

Sternoclavicular (SC) joint

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2
Q

Which joint firmly attaches the scapula to clavicle?

A

Acromioclavicular (AC) joint

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3
Q

Which joint is not a true anatomic joint, but an interface between bones? Its movements are linked to the movements at the SC and AC, the position of the scapula provides the base for the GH joint.

A

Scapulothoracic joint

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4
Q

Which joint is the most distal and mobile portion of the whole complex?

A

Glenohumeral joint (GH)

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5
Q

A series of kinematic links cooperate to maximize range of motion; weakened painful or unstable link decreases the effectiveness of the entire UE

A

Shoulder Complex

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6
Q

Superior slide of scapula in ____________

A

Elevation

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7
Q

Inferior slide of scapula in _____________

A

Depression

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8
Q

Medial border of the scapula slides anterior/lateral in ______________

A

Protraction

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9
Q

Scapula goes posterior and medial during _____________

A

Retraction

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10
Q

The inferior angle of the scapula rotates superior-lateral direction, glenoid fossa faces upward and UE is elevated during ________________

A

Upward rotation

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11
Q

The inferior angle rotates inferior-medial direction and the UE is lowering during ___________

A

Downward Rotation

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12
Q

What makes up the sternoclavicular joint?

A

Medial end of clavicle, clavicular facet on sternum, superior border of the cartilage of the first rib

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13
Q

What does the basilar joint of UE do?

A

Links axial/appendicular skeleton

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14
Q

Why does the sternoclavicular joint allow for large ROM?

A

Firmly attached

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15
Q

The sternoclavicular joint is made of _________ ___________ tissues

A

Extensive periarticular

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16
Q

What is the shape of the sternoclavicular joint?

A

Irregular saddle shaped, convex and concave with sternal facet reciprocally shaped

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17
Q

The longitudinal diameters extend roughly in the_______ plane between the superior and inferior points of the articular surfaces

A

Frontal

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18
Q

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

A

Transverse

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19
Q

What reinforces the capsule of the shoulder?

A

The anterior and posterior SC ligaments

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20
Q

What are the components of the SC joint? (Ligaments, muscles, discs)

A

Anterior and posterior SC ligaments
Interclavicular ligament
Costoclavicular ligament
Articular disc (50% only)
SCM, Sternothyroid, sternohyoid, and subclavious muscle

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21
Q

How many degrees of freedom in the SC joint?

A

3

Sagittal, frontal, and horizontal

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22
Q

What does the SC joint do?

A

Elevates/depresses; protracts/retracts; rotates

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23
Q

What is the goal of the SC joint?

A

To place scapula in optimal position for head of humerus

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24
Q

What movements of the GH joint involve some movement at the SC joint?

A

All movements

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25
Q

When does the clavicle rotate in all 3 degrees of freedom?

A

UE elevation

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26
Q

What are the osteokinematics of shoulder elevation and depression?

A

Parallel to frontal plane
Axis is near anterior-posterior
35-45 degrees elevation
10 degrees degression
Clavicular motion produces similar in scapula

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27
Q

What are the arthrokinematics of elevation of the shoulder?

A

Convex surface rolls superiorly and slides inferiorly; CC ligament stretched and limits motion

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28
Q

What are the arthrokinematics of depression of the shoulder?

A

Convex surface rolls inferiorly and slides superiorly; interclavicular ligament/ superior portion of capsule stretches

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29
Q

What are the osteokinematics of SC protraction and retraction?

A

Occurs nearly parallel to horizontal plane
Axis - vertical
15-30 degrees each direction
associated with scapular protraction/retraction

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30
Q

Where are the arthrokinematics of protraction and retraction happening?

A

Occurs along SC joint’s transverse diameter

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31
Q

What are the arthrokinematics of retraction?

A

Concave surface of clavicle rolls and slides posteriorly on convex surface of sternum; stretched anterior CC lig and anterior capsule

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32
Q

What are the arthrokinematics of protraction?

A

Occurs in an anterior direction, stretches posterior CC lig and posterior capsule, involves reaching forward

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33
Q

What are the osteokinematics of rotation of the clavicle?

A

Around the bone’s longitudinal axis
UE elevation: posterior rotation 20-35 degrees
as UE returns clavicle returns

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34
Q

What are the arthrokinematics of axial rotation of the clavicle?

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

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35
Q

What is the acromioclavicular joint connecting?

A

Lateral end of clavicle and acromion of scapula

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36
Q

What direction does the clavicular facet on the acromion face?

A

Medial and slightly superior

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37
Q

What type of disc is present in most AC joints?

A

Articular disc of varying forms

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38
Q

What is the capsule of the AC joint reinforced by?

A

Superior and inferior AC ligaments

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39
Q

What provides extrinsic stability for the AC joint?

A

Coracoclavicular ligament

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40
Q

What are the two parts of the coracoclavicular ligament?

A

Trapezoid ligament and conoid ligament

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41
Q

What are the kinematics of the AC joint?

A
  • Subtle motions between scapula and lateral clavicle
  • Optimizes the mobility and fit between scapula and thorax (GH joint)
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42
Q

What are the degrees of freedom of the AC joint?

A

3

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43
Q

What are secondary motions?

A

Rotational adjustment motions to fine tune and position the scapula

NOT USUALLY PERFORMED IN THE CLINIC

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44
Q

What does the upward rotation of the scapula at the AC joint look like?

A

Swings upward and outward relative to the end of the clavicle

  • natural motion as part of elevation
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45
Q

How much upward rotation can we get?

A

Up to 30 degrees

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46
Q

What does downward rotation of the scapula at the AC joint look like?

A

Returning to anatomical position; frontal plane depicted but really scapular plane

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47
Q

What are rotational adjustment movements 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

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48
Q

What are the rotational adjustments in the horizontal plane? What axis?

A

Vertical axis, medial border moves away (internal rotation of glenoid fossa)

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49
Q

What are the rotational adjustments in the sagittal plane? What axis?

A

Medial-lateral axis, inferior angle pivots away (anterior tilting) or reverse (posterior tilting)

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50
Q

Wha happens to the AC joint during protraction?

A

Internally rotates in the horizontal plane; helps align the anterior surface of the scapula with the thorax curved surface

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51
Q

What happens to the AC joint during elevation?

A

Anterior tilting

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52
Q

Why is the scapulothoracic joint not a true joint?

A

No direct contact

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53
Q

Where is the scapula seated

A

between 2nd and 7th ribs. 6 cm lateral to spine

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54
Q

What degree of tilt, upward rotation, & internal rotation does the scapula have?

A

10 degrees of anterior tilt, 5-10 degrees of upward rotation, 30-40 degrees internal rotation

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55
Q

What is large UE ROM largely dependent on?

A

Scapular motion

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56
Q

What is protraction and retraction doing?

A

Protracting clavicle around SC joint, SC varies the amount of internal rotation

  • Summation of horizontal motions at both SC and AC joint
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57
Q

What is upward and downward rotation made up of?

A

The summation of clavicular elevation and SC/Scapular upward rotation

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58
Q

What places the glenoid fossa in postion to support/stabailze the head of the humerus?

A

Upward and downward rotation

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59
Q

How many degrees is considered full upward rotation?

A

60 degrees

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60
Q

What is the shape of the head of the glenohumeral joint?

A

Large and convex

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61
Q

What direction does the fossa face in the GH joint?

A

Anterior

** lateral in scapular plane

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62
Q

What position is the head in in the GH joint?

A

Medially, superiorly, and posteriorly (Normal retroversion)

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63
Q

Where is the fibrous capsule?

A

Rim of glenoid fossa to anatomic neck

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64
Q

Describe the fibrous capsule’s function?

A

Allows mobility

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65
Q

What are some characteristics of the fibrous capsule?

A

Loose fitting, thin and expandable

66
Q

What is the fibrous capsule reinforced by?

A

External ligaments

67
Q

What is it called when the inferior portion of the capsule is slackened in anatomical position?

A

Axillary pouch

68
Q

Where is the synovial membrane in the shoulder?

A

Lines inner wall

69
Q

What lines the intracapsular portion of the tendon of the LHB as it exits into the intertubercle groove?

A

An extension of the synovial membrane

70
Q

What are both the head of the humerus and the glenoid fossa lined with?

A

Articular cartilage

71
Q

What is the potential volume of space in the GH joint?

A

Up to 2 x the size of the humeral head

72
Q

What stabilizes the GH joint?

A

Embedded ligaments provide passive tension

73
Q

What are active forces of the GH joint produced by?

A

Local muscles – specifically the rotator cuff

74
Q

What crosses superiorly over the head of the humerus?

A

LHB

75
Q

Describe glenohumeral capsular ligaments?

A

Fibrous connective tissue, interlacing collagen fibers

76
Q

What do the capsular ligaments of the GH joint do?

A

Limit extremes of rotation and translation, helps keep a negative intra-articular pressure in the GH joint

77
Q

What is the role of the superior GH capsular ligament?

A

Resist external rotation, inferior and anterior translations

78
Q

What is the role of the middle GH capsular ligament?

A

Stabilizes most motions- esp anterior restrain in 45-90degrees of abduction and extremes of external rotation

79
Q

What is the role of the inferior bands of the GH capsular ligaments?

A

supports the suspended humeral head and resists inferior/ anterior-posterior translations

80
Q

How many portions of the inferior bands of GH capsular ligament are there? where are they taut?

A

3

Taut in 90 degrees of abduction

81
Q

What does the coracohumeral ligament connect?

A

Coracoid process and the greater tubercle

82
Q

What does the coracohumeral ligament blend with?

A

Superior capsule and supraspinatus tendon

83
Q

When is the coracohumeral ligament taut?

A

In anatomical position

84
Q

What does the coracohumeral ligament restrain?

A

Inferior translation and external rotation of the humeral head

85
Q

Where does the superior GH ligament attach on the humerus?

A

Anatomic neck

86
Q

When is the superior GH ligament taut?

A

External rotation, inferior and anterior translations of the humeral head

87
Q

What is the distal attachment of the middle GH ligament?

A

Anatomic neck, blends with subscapularis tendon

88
Q

What makes the GH ligament taut?

A

Anterior translation of humeral head with abduction, external rotation

89
Q

Where is the distal attachment of the inferior GH ligament?

A

Anatomic neck

90
Q

When is the inferior GH ligament taut?

A

90 degrees of abduction

91
Q

Where is the distal attachment of the coracohumeral ligament?

A

Anterior side of greater tubercle, blends with superior capsule and supraspinatus tendon

92
Q

What makes the coracohumeral ligament taut?

A

Inferior translation of the humeral head, external rotation

93
Q

What do the rotator cuff muscles do?

A

Provide structural support for the capsule

94
Q

Which rotator cuff muscle is the thickest?

A

Subscapularis

95
Q

Where are the 2 regions of vulnerability of the rotator cuff?

A
  • rotator cuff interval inferior to the supraspinatus and subscapularis
96
Q

What reinforces the rotator cuff interval?

A

Long head of the biceps, coracohumeral ligament, and the superior/middle capsular ligaments

97
Q

Where is the origin of the long head of the biceps?

A

Supraglenoid tubercle and labrum

98
Q

What does the long head of the biceps restrict?

A

Anterior translation of humeral head

99
Q

What does the force generated through the tendon of the long head of the biceps resist? When is it needed?

A

Anterior translation, needed in abduction

100
Q

What is the glenoid labrum?

A

Fibrocartilaginous ring

101
Q

What creates 50% of the depth of the glenoid fossa?

A

Glenoid labrum

102
Q

What is the job of the glenoid labrum?

A

Stabilizer

103
Q

What structures deepen and reinforce the GH joint?

A

joint capsule / GH capsular ligaments

Coracohumeral ligament

rotator cuff muscles (SITS)

Long head of the biceps

Glenoid labrum

104
Q

What do superior capsular structures (SCS) provide the shoulder?

A

ligamentous support

105
Q

What can disruption and deformation of the superior capsular structures (SCS) produce?

A

Humeral head can drift inferiorly - leads to subluxation or dislocation

106
Q

What is the coracoacromial arch formed by?

A

Coracromial ligament and acromion process

107
Q

What is depth of the the coracoacromial arch with the arm at rest by the side?

A

1 cm in adults

108
Q

What is in the coracoacromial arch?

A

Supraspinatus muscle, subacromial bursa, long head of the biceps, and superior capsule

109
Q

Where are the bursas generally around the GH joint?

A

Situated where significant frictional forces develop such as between tendons, capsule and bone, muscle and ligament, or 2 adjacent muscles

110
Q

How many bursa are superior to the humeral head?

A

2

111
Q

Where is the subacromial bursa? What does it do?

A

Above supraspinatus

protects supraspinatus from acromial bone

112
Q

What does the subdeltoid bursa do?

A

Limits friction forces between deltoid and SS tendon/humeral head

113
Q

How many degrees of freedom in the shoulder?

A

3

114
Q

How many degrees is anatomic position of the shoulder?

A

0

115
Q

Describe abduction kinematics?

A

Rotation of the humerus in the frontal plane

AP axis

convex head of humerus rolls superiorly, slides inferiorly

116
Q

Describe adduction kinematics?

A

Convex head of humerus rolls inferiorly, slides anteriorly

AP axis

117
Q

Why does the larger head not fall off during abduction and adduction?

A

Sliding

118
Q

What stretches the axillary pouch?

A

the humeral head in 90 degrees abduction

119
Q

What is the height of the subacromial space at 20 degrees of abduction?

A

7.5 mm

120
Q

What is the height of the subacromial space at 85 degrees of abduction?

A

2.6 mm

121
Q

What is the height of the subacromial space at 150 degrees of abduction?

A

5mm

122
Q

Where is the SS potentially compressed in abduction? (Degrees)

A

35-70 degrees

123
Q

What is adhesive capsulitis?

A

Excessive thickening or stiffness in ICL

124
Q

What does adhesive capsulitis limit? Why?

A

slide of humeral head, jams against coracoacromial arch

125
Q

How many degrees can the humeral head move without any slide?

A

22 degrees

126
Q

What is impingement syndrome?

A

Unnatural and repeated compression/ abrasions damages the SS tendon, subacromial bursa, or superior parts of the capsule

127
Q

What syndrome can repeated compression lead to?

A

Impingement syndrome

128
Q

What is flexion arthrokinematics?

A

Rotation of the humerus in the sagittal plane, med-lateral axis

129
Q

How many degrees of flexion are typical?

A

120 degrees GH
180 complex

130
Q

How many degrees of extension are typical?

A

65 degrees active
80 degrees passive

131
Q

What does the scapula do during extenion?

A

Anterior tilt

132
Q

What are the degrees of internal rotation in neutral?

A

75-85

133
Q

What are the degrees of external rotation?

A

60-70 degrees

134
Q

What is the roll and slide with external rotation?

A

Rolls posteriorly and slides anteriorly

135
Q

What is the roll and slide for internal rotation?

A

Rolls anteriorly, slides posteriorly

136
Q

What is 90 degrees of abduction external rotation primarlly?

A

Spinning

137
Q

What is the first kinematic principle of shoulder abduction?

A

active shoulder abduction of 180 degrees occurs as a result of simultaneous 120 degrees of GH joint abduction and 60 degrees of scapulothoracic upward rotation

138
Q

What is the second kinematic principle of shoulder abduction?

A

The 60 degrees of upward rotation of the scapula is the result of a simultaneous elevation at the SC joint and rotation at the AC joint

139
Q

What is the third principle of shoulder abduction?

A

the clavicle retracts at the SC joint

140
Q

What is the fourth kinematic principle of shoulder abduction?

A

The upwards rotating scapula posteriorly tilts and externally rotates slightly with full shoulder Abd

141
Q

What is the fifth kinematic principle of shoulder abduction?

A

The clavicle posteriorly rotates around its own axis

142
Q

What is the sixth kinematic principle of shoulder abduction?

A

The GH joint externally rotates

143
Q

What is scapulohumeral rhythm?

A

Natural rhythm between GH abduction and scapulothoracic upward rotation

144
Q

When is the scapulohumeral rhythm constant?

A

after 30 degrees of abduction

145
Q

What is the ration for scapulothumeral rhythm?

A

2:1 - every 3 degrees abduction = 2 degrees at GH joint and 1 degrees at scapulothoracic for upward rotation

146
Q

What is the ration for the full arc of 180 regarding scapulohumeral rhythm?

A

120 GH / 60 ST

147
Q

What is the 60 degrees of the scapula a result of (think SC and AC joints)?

A

elevation of the clavicle at the SC joint and upward rotation of the scapula at the AC joint

148
Q

how many degrees does the sternoclavicular joint elevate during 180 degrees of full abduction?

A

30 degrees

149
Q

What does the clavicle do at the SC joint during full abduction

A

Retracts 15-20 degrees

150
Q

What plane does the clavicle move in during full abduction?

A

frontal plane

151
Q

What does the scapula do at full abduction?

A

Tilts posteriorly and slightly rotates outward

152
Q

What is the position of the scapula at rest (degrees)?

A

Anterior tilted 10 degrees

internally rotated 30-40 degrees

153
Q

What does the scapula do with abduction (degrees)?

A

Posteriorly tilts 20 degrees
rotates AC and SC joints

154
Q

What does the posterior tilting and external rotation of the scapula help with during abduction?

A

Keeps scapula flush with thorax, orients the fossa, moves the coracoacromial arch away from humeral head

155
Q

How many degrees does the clavicle rotate posteriorly during full abduction?

A

20-35 degrees

156
Q

What can cause reduced rotation of the clavicle during abduction?

A

Subacromial impingement

157
Q

Which muscle makes the coracoclavicular ligament taut with scapular upward rotation?

A

Serratus anterior

158
Q

What does the humerus naturally do during abduction

A

externally rotates

159
Q

What does the rotation of the humerus during abduction allow for?

A

The greater tubercle to pass posterior to the acromion

160
Q

What is the range for the external rotation of the humerus during abduction? (degrees)

A

25-50 with the majority before 70-80 degrees of abduction

Biomechanics Exam 3 (3 decks)

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