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Functional Anatomy > Sternoclavicular and Acromioclavicular Joint- Palastanga > Flashcards

Sternoclavicular and Acromioclavicular Joint- Palastanga Flashcards

1
Q

Classification of the sternoclavicular (sc) joint

A

Functionally a ball and socket but anatomically is a synovial double plane (or saddle)

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2
Q

Articular surfaces of the sternoclavicular joint

A

Medial end of clavicle with the clavicular notch at the superolateral angle of the sternum and adjacent upper medial surface of the 1st costal cartilage

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3
Q

What provides congruency to the sc joint

A

The inta-articular fibrocartilagenous disc

Joint surfaces give little congruency

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4
Q

Features of the intra-articular disc of the sc joint

A

Thinner centrally where may be perforated
Attached circumstantially to the joint capsule
Attached to superior and posteriorly to medial end of clavicle and inferiorly to 1st costal cartilage

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5
Q

Function of the intra-articular disc of sc joint

A

Increase congruency of the joint
Provide cushioning between articular surfaces
Ligamentous- fibrous around circumference so holds clavicle against sternum when subjected to forces from upper limb

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6
Q

What strengthens the SC joint capsule

A

Anterior sternoclavicular ligament
Posterior sternoclavicular ligament
Interclavicular ligament (between the 2 clavicles)
Costoclavicular ligament- very strong

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7
Q

What is limited by the costoclavicular ligament

A

Elevation of the capsule

Also compensates for the inferior weakening of the capsule

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8
Q

What confers the most stability to the SC joint

A

The integrity of it’s surrounding ligaments, particularly costoclavicular

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9
Q

Movement of the SC joint occurs i how many degrees of freedom

A

3
elevation/ depression
protraction/ retraction
axial rotation

Is really the lateral end of the clavicle that moves with small reciprocal movements at the SC joint

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10
Q

Describe elevation/ depression of the sc joint

A

Occurs at an axis which runs horizontally and anterolaterally through the costoclavicular ligament
Total angular range of 60degrees
Elevation- lateral end up medial end down
Depression- lateral end down medial end up

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11
Q

What limits elevation/ depression of the sc joint

A

Elevation- costoclavicular ligament and tone of subclavius

Depression- tension in interclavicular ligament and intra-articular disc

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12
Q

Describe protraction/ retraction of the sc joint

A

Axis of movement lies in a vertical plane running obliquely inferolaterally through middle part of costoclavicular ligament
Total angular ROM of 35degrees
Protraction- lateral end moves forward and medial end posteriorly
Retraction- lateral end moves backward and medial end anteriorly

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13
Q

Limits to pretraction/ retraction of the sc joint

A

Protraction (post movement of medial end)- poterior sternoclavicular and costoclavicular ligament
Retraction (ant movement of medial end)- anterior sternoclavicular and costclavicular ligament

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14
Q

How does axial rotation of the SC joint differ from elevation/depression/protraction/retraction

A

Axial rotation is entirely passive where others are brought about my active muscle movement

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15
Q

How is axial rotation at the SC joint brought about

A

By rotation of the scapula transferred via the coracoclavicular ligament
Cannot happen as a pure movement, is always accompanied by other movement of the joint

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16
Q

Degree of axial rotation of the SC joint and what allows this

A

40 to 60 degrees depending on position of clavicle

Allowed by relative incongruency of joint, intra-articular disc and relative laxness of capsule

17
Q

Classification of the acromioclavicular (ac) joint

A

Synovial plane

18
Q

Articular surfaces of the ac joint

A

Oval flat or slightly convex facet on lateral head of clavicle with similar flat or concave facet on anteromedial border of the acromion

19
Q

How does the joint axis run through the ac joint

A

From anterolateral to posteromedial
Clavicular facet faces posterolaterally
Acromion facet faces anteromedially

20
Q

What of the anatomy of the AC joint predisposes it to displacement of the acromion downwards and under the clavicle during dislocation?

A

Over-riding of the lateral end of the clavicle over the acromion and slope of their articular surfaces

21
Q

Describe the intra-articular disc of the ac joint

A

Wedge-shaped fibrocatilagenous disc present in most, only rarely forms a complete partition
May not be present but when is is attached to the superior aspect of the joint capsule and hangs down

22
Q

Function of the ac joint intra-articular disc

A

Partially compensates for the lack of congruity of the joint surfaces (but not by much)

23
Q

What may strengthen the capsule of the ac joint

A

Debated whether or not is strengthened by the superior and inferior acromioclavicular ligaments, which may just be thickenings of the joint capsule

Strength of joint is mainly provided by the coracoclavicular ligament- an extracapsular accessory ligament

24
Q

Where is the coracoclavicular ligament found

A

Sits medial to the ac joint and anchors the lateral end of the clavicle to the coracoid process
Separated into conoid and trapezoid (more lateral) parts which are usually continuous with eachother

25
Q

Describe the arrangement of the coracoclavicular ligament

A

Trapezoid part stronger than conoid
Anteriorly may not be continuous and have synovial bursa in the space
Trapezoid and conoid sit at right angle to eachother as lie in different planes

26
Q

What movements are limited by the coracoclavicular ligament

A

Conoid limits forward movement of scapula
Trapezoid limits posterior movement of scapula
Both prevent the acromion being carried medially under the lateral end of the clavicle under the pressure of lateralising forces

27
Q

What provides the stability of the ac joint

A

The coracoclavicular ligament

28
Q

What type of movement is permitted at the ac joint

A

Passive movement only, by moving the shoulder blade move the clavicle through the ac joint
Has 3 degrees of freedom of gliding movements

Complex- see Palastanga pp 110

29
Q

What is the purpose of the pectoral girdle

A

To increase the range of movement of the shoulder joint as a whole by changing position of glenoid fossa with respect to the chest wall

30
Q

Muscles retracting the pectoral girdle

A

Rhomboid major/ minor

Trapezius (middle fibres)

31
Q

Muscles protracting the pectoral girdle

A

Serratus anterior

Pec minor

32
Q

Muscles elevating the pectoral girdle

A

Trapezius (upper fibres)

Levator scapulae

33
Q

Muscles depressing the pectoral girdle

A

Trapezius (lower fibres)

34
Q

Muscles laterally rotating the scapula

A

Trapezius (upper and lower fibres)

Serratus anterior

35
Q

Muscles medially rotating the scapula

A

Rhomboid major, minor
Pec minor
Levator scapulae

Functional Anatomy (18 decks)

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