L9: The shoulder, osteology of the scapula, clavicle and proximal humerus Flashcards
What types of bone is the scapula?
Irregular bone
Triangular flat bone
What does the scapular articulate with?
Glenoid cavity and humerus–> glenohumeral joint
Acromion and clavicle–> acromioclavicular joint
Anterior surface of scapular and rib cage–> Scapulothoracic joint (articulation) (not a true joint)
Describe the anatomy of the anterior surface of the scapula?
Anterior surface –> costal surface
Subscapular fossa–> Large concave depression
Coracoid process–> Superolateral surface , projects anterior laterally
Scapular notch–> medial to coracoid process
Describe the anatomy of the posterior surface of the scapula?
Spine–> prominent feature, runs transversely across the scapular
Acromion–> large projection, lateral, arches over the glenohumeral joint, articulates with the clavicle (acromioclavicular joint)
Infraspinous fossa–> depression below spine of scapula
Supraspinous fossa–> depression above the spine of scapula
Describe the anatomy of the lateral surface of the scapula?
Glenoid fossa (cavity)--> shallow cavity, located superiorly on the lateral border (articulates with head of humerus) Supraglenoid tubercle--> roughening superior to glenoid fossa (origin of long head of Biceps brachii) Infraglenoid tubercle--> roughening inferior to glenoid fossa (origin of long head of triceps brachii)
Does the scapular fracture?
It can but its rare–> high speed collision, indication of severe chest trauma
Doesn’t typically require fixation–> muscles hold fragments in place
Where is the clavicle located?
Between the manubrium of the sternum and the acromion of the scapula
What are the functions of the scapula?
- Attaches the upper limb to the trunk as part of the shoulder girdle
- Protects the underlying neurovascular structures supplying the upper limb
- Transmits forces from the upper limb to the axial skeleton
What type of bone is the clavicle classified as?
Long bone
Describe the anatomy of the clavicle?
S shaped, medial (sternal) end and lateral (acromial) end
Medial portion- convex anteriorly
Lateral portion- concave
Shaft–> between two ends
Sternal end–> facet for articulation
Inferior surface of sternal end–> rough oval depression (costoclavicular ligament)
Acromial end–> conoid tubercle and trapezoid line
What is the name of the joint between the clavicle and the scapula?
Acromioclavicular joint
What type of joint is the acromioclavicular joint? What are the atypical features of this joint?
A plane-type synovial joint
Joint capsule–> loose fibrous layer, lined by synovial membrane secrete synovial fluid
Posterior aspect of joint–> reinforced by trapzeius fibres
Atypical features
–> Articular surfaces lined with fibrocartilage
–> Joint cavity is partially divided by an articular disc (wedge of fibrocartilage suspended from the upper part of the capsule)
What ligaments help to strengthen the acromioclavicular joint?
Intrinsic–> Acromioclavicular ligament
Extrinsix–> coracoclavicular ligament formed from conoid ligament and trapezoid ligament
What are the attachment sites for the acromioclavicular ligament?
Horizontal
From acromion to the lateral clavicle
Superficial to joint capsule
Reinforces superior aspect
What are the attachment sites for the coracoclavicular ligament?
Conoid ligament–> Vertically - Coracoid process of scapula to the conoid tubercle of the clavicle
Trapezoid ligament–> Vertically - Coracoid process of scapula to the trapezoid line of the clavicle
What does the acromioclavicular joint allow?
Small degree of axial rotation
Anteroposterior movement
No muscles act directly –> passive movements
What is name of the joint between the clavicle and the manubrium of the sternum?
Sternoclavicular joint
What type of joint is the sternoclavicular joint?
Synovial joint –> saddle type
Between the manubrium of the sternum, sternal (medial) end of clavical (and the 1st costal cartilage)
Articular surfaces lined with fibrocartilage
Separated into two compartments by the fibrocartilagenous articular disc –> manubrium and clavicle can slide over each other
What type of movements are permitted by the sternoclavicular joint?
Large degree of mobiltiy–> but a very strong joint
Elevation of shoulder over 90 degrees
Depression of the shoulder
Protraction of the shoulder (anteriorly)
Retraction of the shoulder (posteriorly)
Rotation–> arm over head, flexion at glenohumeral joint, clavicle rotates passively because of scapular, force transmitted by the coracoclavicular ligaments
What does the humerus articulate with?
Head articulates with the glenoid fossa (cavity)–> glenohumeral joint
Distal end articulates with the head of radius and trochlear notch of ulna
Describe the anatomy of the proximal humerus?
Head–> faces medially, superiorly and posteriorly
Anatomical neck–> separates head from tubercles, attachment of articular capsule, region of epiphseal growth plate
Surgical neck–> beneath the tubercles
Greater and lesser tubercles
–> Greater–> posterolateral aspect, rounded projection
–> Lesser–> smaller more medially located
Intertubercular sulcus–> depression, separates the two tubercles, edges known as lips
Which of the necks of the humerus is more commonly fractured? What is a consequence of fracture to this neck?
The surgical neck
May cause damage to the axillary nerves and posterior circumflex humeral artery
Axillary nerve damage–> paralysis to deltoid and teres minor
Describe the anatomy of the shaft of the humerus?
Circular cross section proximally
Flattened cross section distally
Lateral side roughened–> deltoid tuberosity– muscle attach
Radial (spiral) groove–> shallow depression, runs diagonally on posterior surface –> radial nerve and profunda brachial artery lie in this groove
What muscles attach to the humerus along the shaft?
Anterior aspect–> coracobrachialis, deltoid, brachialis and brachioradialis
Posterior aspect–> Medial and lateral heads of the triceps