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
What type of joint is the glenohumeral joint?
Synovial joint
Ball and socket
Head of humerus covered in hyaline cartiliage
Glenoid fossa- shallow- line with cartilgae –> facilitates motion and flexibility, at expense of stability (easily dislocated)
What helps to stabilise the glenohumeral joint?
Glenoid labrum–> Rim of fibrocartilage–> deepens the socket reducing risk of dislocation
Joint capsule relatively loose–> reinforces superiorly by rotator cuff muscles (inferior- weakest- no reinforcement)
Glenohumeral ligaments–> superior, middle and inferior –> reduce risk of anterior dislocation
Coracohumeral ligament–> coracoid process to greater tubercle of humerus
What is the function of the transverse humeral ligament and the coraco-acromial ligament?
Prevent bowstringing of tendons when muscle is in use
Transverse humeral ligament–> between greater and lesser tuberosity–> passage on long head of biceps brachii tendon
Coracoacromial ligament–> between coracoid process and acromion–> roof of subacromial space–> passage of supraspinatus tendon –> prevents superior dislocation
How are the muscle of the shoulder region classified?
Extrinsic–> originate in torso, insert onto bone in the shoulder (scapula, clavicle or humerus)
Intrinsic–> originate from scapular and/or clavicle and insert onto the humerus
How are the extrinsic muscle of the shoulder further classified?
Superficial: Trapezius or latissimus dorse
Deep: Levator scapulae, rhomboid major and rhomboid minor
What is the origin, insertion, innervation and function of the Trapezius?
Broad, flat, triangular muscle
Most superficial
O: External occipital protuberance, nuchal ligament and spinous process of C7-T12
I: Clavicle, acromion and spine of scapula
Innervation: Spinal accessory nerve and propioception from C3 and C4 spinal nerves
F:
- -> upper fibres–> elevate the scapular
- -> middle fibres–> retract the scapular
- -> lower fibres–> pull scapular inferiorly
What is the origin, insertion, innervation and function of the Lattisimus dorsi?
Wider area of lower back
Deep to trapezius
O: Spinous process of T6-12, iliac crest, thoracolumbar fascia, inferior 3 ribs
I: Tendon onto the intertubercular sulcus of humerus
Innervation: Thorcodorsal nerve
F: Extends, adduct and medially rotates the arm
What is the origin, insertion, innervation and function of the Levator scapulae?
Small strap like muscle
Deep to trapezium
Superficial to rhomboid muscles
O: transverse process of C1-C4 vertebrae
I: Medial border of scapula
Innervation: Dorsal scapular nerve
F: Elevate the scapula
What is the origin, insertion, innervation and function of the Rhomboid minor?
Smaller than rhomboid major
Sits superiorly
O: Spinous processes of C7 to T1 vertebrae
I: Medial border of scapula at level of spine of scapula
Innervation: Dorsal scapular nerve
F:
- -> Retracts the scapula
- -> rotates medial border so glenoid fossa faces inferiorly, helps return it to normal position after arm abduction >90
What is the origin, insertion, innervation and function of the Rhomboid major?
O: Spinous process of T2- 5
I: medial border of scapula, inferior to spine of scapular, superior to inferior angle of scapular
Innervation: dorsal scapular nerve
F: same as rhomboid minor
- -> retracts the scapular
- -> rotate the medial border so that the glenoid fossa faces inferiorly, helpss return to normal position after arm abduction >90
How many intrinsic muscles of the shoulder are there?
6 intrinsic muscles –> originate on bone in shoulder (scapula or clavicle), insert onto humerus
Deltoid, Teres major, rotator cuff muscles; supraspinatus, infraspinatus, subscapularis and teres minor)
What is the origin, insertion, innervation and function of the deltoid muscle?
Functionally divided into anterior, middle and posterior parts
O: anterior, lateral 1/3 of clavicle, acromion and spine of scapula
I: deltoid tuberosity
Innervation: Axillary nerve
F:
- -> Anterior fibres–> flex and medially rotate the arm
- -> Middle fibres–> abduct the arm 15-90 degrees
- -> Posterior fibres–> extend and laterally rotate the arm at shoulder
What is the origin, insertion, innervation and function of the Teres major?
Inferior border of quadrangular space
O: Posterior surface of inferior angle of scapula
I: Medial lip of intertubercular groove of humerus (anteromedial surface)
Innervation: lower subscapular nerve
F: Adduct and extends arm
–> medially and internally rotates
What are the rotator cuff muscles?
Group of four muscles
Pull the humeral head into the glenoid fossa
Large amount of dynamic stability
What is the origin, insertion, innervation and function of the supraspinatus?
O: Supraspinous fossa
I: Greater tubercles of humerus
Innervation: Suprascapular nerve (branch of upper trunk if BP –> C5, C6)
F: Abducts the arm from 0-15 degrees, assists deltoid 15-90 degrees
What is the origin, insertion, innervation and function of the Infraspinatous?
O: Infraspinous fossa
I: Greater tubercle between insertion of supraspinatous and teres minor
Innervation: Suprascapular nerve
F: Laterally rotates the arm
What is the origin, insertion, innervation and function of the subscapularis?
O: subscapular fossa (costal surface)
I: Lesser tubercle of humerus
Innervation: Upper and lower subscapular nerves
F: Medially rotates the arm
What is the origin, insertion, innervation and function of the Teres minor?
O: Posterior surface adjacent to lateral border (superior to teres major)
I: Greater tubercle, inferior to infraspinatus
Innervation: Axillary nerve (C5, 6)
F: Laterally rotates arm
Where is the ‘arm’ located?
Distal to the shoulder
Proximal to the elbow
What are the muscles of the arm?
Anterior compartment: Biceps Brachii, Brachialis, and Coracobrachialis –> BBC muscles
Posterior compartement: Triceps Brachii
What innervates the anterior compartment of the arm?
Musculocutaneous nerve C5, 6 and 7
What is the origin, insertion, innervation and function of the biceps brachii?
No attachment to the humerus
O: Long head= supraglenoid tubercle passes through the should joint through the capsule
Short head= coracoid process
I: Unite to form a single muscle belly, inserts onto radial tuberosity via biceps tendon
–> deep fascia via bicipital aponeurosis
F: Strong supinator of forearm at radioulnar joint –_ flexes arm at elbow and shoulder joint
Innervation: Musculocutaneous nerve (C5, 6 and 7)
What happens when someone ruptures there Biceps brachii?
Normally long head near to the scapular origin
Reported as ‘snap’ in the shoulder region
Flexion at elbow produces lump in lower arm
Unopposed contracted muscle belly - Popeye sign
Not much muscle weakness–> supinator (supination) brachioradialis (flexion)
Weightlifters can rupture distal tendon of biceps brachii