Musculoskeletal: Anatomy - Shoulder and arm

Question 1

What is the pectoral girdle?

Answer 1

Bony ring, incomplete posteriorly, formed by scapulae and clavicles, and completed anteriorly by manubrium

Question 2

When in anatomical position, at what vertebral level does the superior angle of the scapula lie?

Answer 2

T2

Question 3

When in anatomical position, at what vertebral level does the inferior angle of the scapula lie?

Answer 3

T7

Question 4

When in anatomical position, at what vertebral level does the medial end of the root of the scapular spine lie?

Answer 4

Opposite the spinous process of T3

Question 5

What is the weakest part of the clavicle?

Answer 5

Junction of middle and lateral thirds

Question 6

Describe the typical presentation of clavicular fracture

Answer 6

Medial aspect superiorly directed due to action of sternocleidomastoid
Lateral aspect drops due to weight of upper limb (patients hold upper limb on affected side with “good” arm)
May get overlapping of fragments as lateral fragment is pulled medially by adductor muscles of arm (e.g. pectoralis major)

Question 7

What is the first long bone to ossify?

Answer 7

Clavicle via intramembranous ossification beginning during 5th and 6th embryonic weeks

Question 8

Which long bone is the last to completely ossify? What is the clinical relevance?

Answer 8

Clavicle: secondary ossification centre appears at sternal end between 18-25yrs, completely fuses between 25-31yrs
Small epiphysis may be present at acromial end of clavicle and should not be mistaken for a fracture

Question 9

Which parts of the humerus are in direct contact with major nerves of the upper limb?

Answer 9

Surgical neck: axillary nerve
Radial groove (humeral shaft): radial nerve
Distal humerus: median nerve
Medial epicondyle: ulnar nerve

Question 10

What nerves are at risk during axillary node dissection?

Answer 10

Long thoracic
Thoracodorsal

Question 11

What deformity is seen with injury to the long thoracic n.?

Answer 11

Winged scapula (supplies serratus anterior)

Question 12

What deformity is seen with injury to the thoracodorsal n.?

Answer 12

No deformity but weakened medial rotation and adduction of arm

Question 13

What are prefixed and postfixed variations of the brachial plexus? What is the clinical significance of a postfixed brachial plexus?

Answer 13

Prefixed: C4-8
Postfixed: C6-T2 (inferior trunk may be compressed by first rib)

Question 14

What is Erb’s palsy? What does it signify and what is the typical mechanism of injury?

Answer 14

Injury to superior brachial plexus (C5-6)
Results in paralysis of deltoid, biceps and brachialis (supplied by C5-6) and decreased sensation to lateral forearm
Produces “waiter’s tip” deformity: shoulder adducted, elbow extended, wrist flexed, arm medially rotated
Can occur during delivery of neonate or if thrown from e.g. horse or motorbike and landing on shoulder causing head and neck to stretch apart

Question 15

What is hyperabduction syndrome? What is the mechanism and what are the signs and symptoms?

Answer 15

Caused by compression of axillary vessels and nerves with prolonged hyperabduction of arm (e.g. when painting ceiling)
Mechanism: cords impinged between coracoid process and pec minor tendon
Symptoms: pain down arm, numbness, paraesthesia, erythema, hand weakness, ischaemic of upper limb and distension of superficial veins due to axillary artery/vein compression

Question 16

What is Klumpke paralysis? What is the typical mechanism of injury and what are the signs and symptoms?

Answer 16

Inferior brachial plexus injury (C8-T1)
When upper limb suddenly pulled superiorly (e.g. baby during delivery)
Affects short muscles of hands causing claw hand (ulnar palsy)

Question 17

Describe the seven named fascia of the proximal upper limb and pectoral region

Answer 17

1. Pectoral fascia: invests pec major and is continuous inferiorly with fascia of anterior abdominal wall
2. Axillary fascia: as pectoral fascia leaves lateral border of pec major it becomes the axillary fascia, this forms the floor of the axilla
3. Clavipectoral fascia: deep to pectoral fascia, descends from clavicle and encloses subclavius and pec minor
4. Deltoid fascia: over superficial surface of deltoid from clavicle, acromion and scapular spine; numerous septa penetrate between fascicles of deltoid; inferiorly continuous with pectoral fascia anteriorly and infraspinous fascia posteriosly
5. Supraspinous fascia
6. Infraspinous fascia
7. Brachial fascia: continuous superiorly with deltoid, pectoral, axillary and infraspinous fascia; attached inferiorly to epicondyles of humerus and olecranon of ulna; two intermuscular septa (medial and lateral) extend from deep surface of brachial fascia to central shaft and medial and lateral supra-epicondylar ridges of humerus to divide arm into anterior and posterios compartments

Question 18

Describe in detail the clavipectoral fascia

Answer 18

Includes costocoracoid membrane between subclavius superiorly and pec minor inferiorly: pierced by lateral pectoral n.
Suspensory ligament of axillary inferiorly to pec minor: supports axillary fascia and pulls it and overlying skin upward during arm abduction to form the axillary fossa (armpit)

Question 19

Which nerve pierces the costocoracoid membrane? What is the function of this nerve?

Answer 19

Lateral pectoral n. (primarily supplying pec major)

Question 20

Describe the superficial and deep venous drainage of the upper limb

Answer 20

Superficial:
- Cephalic and basilic veins originate in subcut tissue of dorsum of hand from dorsal venous network
- Cephalic vein ascends laterally through forearm and arm then joins terminal part of axillary vein
- Basilic vein ascends medially through forearm and inferior arm then passes deeply near junction of middle and inferior thirds of arm, merges with accompanying veins of axillary artery to form axillary vein
- Medial antebrachial vein is highly variable, begins at base of dorsum of thumb and ascends in anterior forearm between cephalic and basilic veins
Deep:
- Internal to deep fascia and accompany major arteries (share names: ulnar, radial, anterior and posterior interosseous, brachial, and profunda brachii veins; also paired veins accompanying all branches of axillary artery e.g. thoraco-acromial)
Connecting:
- Perforating veins connect superficial and deep veins

Question 21

What are the two main superficial veins of the upper limb?

Answer 21

Cephalic
Basilic
Median antebrachial

Question 22

Describe the course of the cephalic vein

Answer 22

Originates from lateral aspect of dorsal venous network
Travels along lateral wrist and anterolateral forearm and arm
Communicates with median cubital vein anterior to elbow (which passes obliquely across cubital fossa to join basilic)
Travels superiorly between deltoid and pec major along deltopectoral groove
Enters clavipectoral triange
Pierces costocoracoid membrane and part of clavipectoral fascia
Joins terminal part of axillary vein

Question 23

Describe the course of the basilic vein

Answer 23

Originates from medial aspect of dorsal venous network
Travels along medial forearm and inferior arm
Then passes deeply near junction of middle and inferior thirds of arm
Pierces brachial fascia and runs superiorly parallel to brachial artery and medial cutaneous nerve of forearm
Merges with accompany veins of axillary artery in the axilla to form axillary vein

Question 24

Describe the course of the median antebrachial vein

Answer 24

Highly variable
Begins at base of dorsum of thumb, curves around lateral wrist and ascends anteriorly in forearm between brachial and cephalic veins
Sometimes divides into medial basilic vein which joins the basilic, and median cephalic vein which joins the cephalic

Question 25

Where do the deep veins of the upper limb originate?

Answer 25

Superficial and deep venous palmar arches

Question 26

Where do the superficial lymphatic vessels of the upper limb originate? What is their subsequent course?

Answer 26

Arise from lymphatic plexuses in skin of fingers, palm, and dorsum of hand Ascend mostly with superficial veins Some vessels accompanying brachial vein enter cubital lymph nodes -> efferent vessels from cubital lymph nodes drain to humeral (lateral) axillary lymph nodes Most vessels accompanying cephalic vein cross proximal arm and anterior shoulder then enter apical axillary lymph nodes (some enter more superficial deltopectoral lymph nodes)

Question 27

Describe the location of the cubital lymph nodes

Answer 27

Proximal to medial epicondyle Medial to basilic vein

Question 28

Describe the course of the deep lymphatic vessels

Answer 28

Accompany the major deep veins (radial, ulnar, brachial) Terminate in humeral axillary lymph nodes

Question 29

Where do the axillary lymph nodes drain to?

Answer 29

Subclavian lymphatic trunk

Question 30

What structures do the deep lymphatic vessels of the upper limb drain?

Answer 30

Joint capsules Periosteum Tendon Nerves Muscles

Question 31

Describe the dermatomes of the upper limb (from C3-T2)

Answer 31

C3-4: base of neck, extending laterally over shoulder C5: lateral arm C6: lateral forearm and thumb C7: middle and ring fingers, centre of posterior forearm C8: little finger, medial hand and forearm T1: medial forearm and inferior arm T2: medial superior arm and skin of axilla

Question 32

Contributing spinal nerves, source, and course and distribution of supraclavicular nerves

Answer 32

Spinal nerves: C3-4 Source: cervical plexus Course: anterior to clavicle, deep to platysma Distribution: skin over clavicle and superolateral pec major

Question 33

Contributing spinal nerves, source, and course and distribution of superior lateral cutaneous n. of arm

Answer 33

Spinal nerves: C5-6 Source: terminal branch of axillary n. Course: beneath posterior margin of deltoid Distribution: skin over lower part of deltoid and lateral midarm

Question 34

Contributing spinal nerves, source, and course and distribution of inferior lateral cutaneous n. of arm

Answer 34

Spinal nerves: C5-6 Source: radial n. (or posterior cutaneous n. of arm) Course: perforates lateral head of triceps and passes close to cephalic vein Distribution: skin over inferolateral arm

Question 35

Contributing spinal nerves, source, and course and distribution of posterior cutaneous n. of arm

Answer 35

Spinal nerves: C5-8 Source: radial n. (in axilla) Course: posterior to and communicates with intercostobrachial n. Distribution: skin on posterior arm to olecranon

Question 36

Contributing spinal nerves, source, and course and distribution of posterior cutaneous n. of forearm

Answer 36

Spinal nerves: C5-8 Source: radial n. (with inferior lateral cutaneous n. of arm) Course: perforates lateral head of triceps and descends laterally in arm Distribution: skin of posterior forearm to wrist

Question 37

Contributing spinal nerves, source, and course and distribution of lateral cutaneous n. of forearm

Answer 37

Spinal nerves: C6-7 Source: musculocutaneous n. (terminal branch) Course: lateral to biceps tendon and deep to cephalic vein Distribution: skin of anterolateral forearm to wrist

Question 38

Contributing spinal nerves, source, and course and distribution of medial cutaneous n. of forearm

Answer 38

Spinal nerves: C8-T1 Source: medial cord of brachial plexus (in axilla) Course: medial to brachial artery, pierces deep fascia with basilic vein in midarm, divides into anterior and posterior branches that enter forearm Distribution: skin of anteromedial wrist

Question 39

Contributing spinal nerves, source, and course and distribution of medial cutaneous n. of arm

Answer 39

Spinal nerves: C8-T2 Source: medial cord of brachial plexus (in axilla) Course: communicates with intercostobrachial n. Distribution: skin of medial aspect of distal arm

Question 40

Contributing spinal nerves, source, and course and distribution of intercostobrachial n.

Answer 40

Spinal nerves: T2 Source: 2nd intercostal n. (as its lateral cutaneous branch) Course: extends laterally, communicating with posterior and medial cutaneous nerves of arm Distribution: skin of axilla and medial aspect of proximal arm

Question 41

What are the four anterior axio-appendicular muscles?

Answer 41

1. Pec major 2. Pec minor 3. Serratus anterior 4. Subclavius

Question 42

Proximal and distal attachments, innervation, and main action of pec major

Answer 42

Proximal: clavicular head to anteromedial half of clavicle; sternocostal head to anterior sternum, costal cartilage ribs 1-6, aponeurosis of external oblique Distal: lateral lip intertubercular sulcus of humerus Innervation: lateral and medial pectoral n.; clavicular head C5-6, sternocostal head C7-T1 Main action: adduction and medial rotation of humerus, draws scapular anteriorly and inferiorly

Question 43

Proximal and distal attachments, innervation, and main action of pec minor

Answer 43

Proximal: ribs 3-5 near costal cartilage Distal: superomedial coracoid process of scapula Innervation: medial pectoral n. (C8-T1) Main action: draws scapula anteriorly and inferiorly to stabilise

Question 44

Proximal and distal attachments, innervation, and main action of subclavius

Answer 44

Proximal: junction of 1st rib and costal cartilage Distal: inferior surface of middle third of clavicle Innervation: nerve to subclavius (C5-6) Main action: anchors and depresses clavicle (resists SCJ dislocation)

Question 45

Proximal and distal attachments, innervation, and main action of serratus anterior

Answer 45

Proximal: lateral ribs 1-8 Distal: anterior surface of medial border of scapular Innervation: long thoracic n. (C5-7) Main action: protracts and rotates scapula, holds against thoracic wall

Question 46

What forms the deltopectoral groove? What structures run here?

Answer 46

Pec major and deltoid Cephalic vein runs here

Question 47

What structures form the clavipectoral triangle?

Answer 47

Pec major, deltoid and clavicle

Question 48

What are the main actions of the clavicular and sternocostal heads of pec major in isolation?

Answer 48

Clavicular: flexes arm Sternocostal: extends arm from flexed position

Question 49

Name the two superficial and three deep posterior axio-appendicular muscles

Answer 49

Superficial: 1. Trapezius 2. Latissimus dorsi Deep: 1. Levator scapulae 2. Rhomboid major 3. Rhomboid minor

Question 50

Proximal and distal attachments, innervation, and main action of trapezius

Answer 50

Proximal: medial third superior nuchal line, external occipital protuberance, nuchal ligament, spinous processes C7-T12 Distal: lateral third of clavicle; acromion and spine of scapula Innervation: motor from spinal accessory nerve (CN XI), proprioception and pain from C3-4 Main action: descending part elevates, ascending part depresses, and middle part retracts scapula

Question 51

Proximal and distal attachments, innervation, and main action of lattisimus dorsi

Answer 51

Proximal: T6-12 spinous processes, thoracolumbar fascia, iliac crest, ribs 9-12 Distal: floor of intertubercular sulcus of humerus Innervation: thoracodorsal n. (C6-8) Main action: extends, adducts, medially rotates humerus

Question 52

Proximal and distal attachments, innervation, and main action of levator scapulae

Answer 52

Proximal: C1-4 transverse processes (posterior tubercles) Distal: medial border of scapula above spine Innervation: dorsal scapular (C4-5) and cervical (C3-4) nerves Main action: elevates and rotates scapula

Question 53

Proximal and distal attachments, innervation, and main action of rhomboid major and minor

Answer 53

Proximal: minor to nuchal ligament and C7 and T1 spinous processes, major T2-5 spinous processes Distal: minor to medial scapular spine, major to medial border of scapula below spine Innervation: dorsal scapular n. (C4-5) Main action: retracts and rotates scapula, fixes scapula to thoracic wall

Question 54

What are the four muscles of the rotator cuff? What are their distal attachments?

Answer 54

Teres minor: inferior facet of greater tubercle Infraspinatus: middle facet of greater tubercle Supraspinatus: superior facet of greater tubercle Subscapularis: lesser tubercle

Question 55

Proximal and distal attachments, innervation, and main action of deltoid

Answer 55

Proximal: lateral third of clavicle; acromion and spine of scapula Distal: deltoid tuberosity of humerus Innervation: axillary n. (C5-6) Action: clavicular flexes and medially rotates, acromial abducts, spinal extends and laterally rotates

Question 56

Proximal and distal attachments, innervation, and main action of infraspinatus

Answer 56

Proximal: infraspinous fossa Distal: middle facet of greater tubercle Innervation: suprascapular n. (C5-6) Action: laterally rotates

Question 57

Proximal and distal attachments, innervation, and main action of supraspinatus

Answer 57

Proximal: supraspinous fossa Distal: superior facet of greater tubercle Innervation: suprascapular n. (C5-6) Action: initiates first 15 degrees of abduction

Question 58

Proximal and distal attachments, innervation, and main action of teres major

Answer 58

Proximal: posterior surface of inferior angle of scapula Distal: medial lip of intertubercular sulcus Innervation: lower subscapular n. (C5-6) Action: adducts and medially rotates, important stabiliser of humeral head in glenoid cavity

Question 59

Proximal and distal attachments, innervation, and main action of teres minor

Answer 59

Proximal: middle part of lateral border of scapula Distal: inferior facet of greater tubercle Innervation: axillary n. (C5-6) Action: laterally rotates

Question 60

Proximal and distal attachments, innervation, and main action of subscapularis

Answer 60

Proximal: subscapular fossa Distal: lesser tubercle Innervation: upper and lower subscapular n. (C5-7) Action: medially rotates, helps hold head of humerus in glenoid cavity

Question 61

What are the six scapulohumeral muscles?

Answer 61

Deltoid Supraspinatus Infraspinatus Teres minor Teres major Subscapularis

Question 62

What is the role of the deltoid when the arm is in full adduction?

Answer 62

Resists inferior displacement of head of humerus (e.g. when lifting/carrying)

Question 63

What clinical appearance is seen with injuries of the long thoracic nerve?

Answer 63

Paralysis of serratus anterior: causes winging of scapula, inability to complete full abduction or elevation (unable to rotate scapula to direct glenoid cavity upwards)

Question 64

What is the typical clinical presentation of thoracodorsal n. injury? What are the usual causes?

Answer 64

Paralysis of lattisimus dorsi: inability to raise trunk when climbing Causes: surgery in inferior axilla, including mastectomy

Question 65

What is the typical clinical presentation of axillary n. injury? What are the usual causes?

Answer 65

Deltoid and teres minor paralysis and atrophy: flattened appearance of shoulder, loss of sensation to lateral upper arm Causes: fracture of surgical neck of humerus, anterior shoulder dislocation, direct compression (e.g. crutches)