Musculoskeletal: Anatomy - Shoulder and arm Flashcards
What is the pectoral girdle?
Bony ring, incomplete posteriorly, formed by scapulae and clavicles, and completed anteriorly by manubrium
When in anatomical position, at what vertebral level does the superior angle of the scapula lie?
T2
When in anatomical position, at what vertebral level does the inferior angle of the scapula lie?
T7
When in anatomical position, at what vertebral level does the medial end of the root of the scapular spine lie?
Opposite the spinous process of T3
What is the weakest part of the clavicle?
Junction of middle and lateral thirds
Describe the typical presentation of clavicular fracture
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)
What is the first long bone to ossify?
Clavicle via intramembranous ossification beginning during 5th and 6th embryonic weeks
Which long bone is the last to completely ossify? What is the clinical relevance?
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
Which parts of the humerus are in direct contact with major nerves of the upper limb?
Surgical neck: axillary nerve
Radial groove (humeral shaft): radial nerve
Distal humerus: median nerve
Medial epicondyle: ulnar nerve
What nerves are at risk during axillary node dissection?
Long thoracic
Thoracodorsal
What deformity is seen with injury to the long thoracic n.?
Winged scapula (supplies serratus anterior)
What deformity is seen with injury to the thoracodorsal n.?
No deformity but weakened medial rotation and adduction of arm
What are prefixed and postfixed variations of the brachial plexus? What is the clinical significance of a postfixed brachial plexus?
Prefixed: C4-8
Postfixed: C6-T2 (inferior trunk may be compressed by first rib)
What is Erb’s palsy? What does it signify and what is the typical mechanism of injury?
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
What is hyperabduction syndrome? What is the mechanism and what are the signs and symptoms?
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
What is Klumpke paralysis? What is the typical mechanism of injury and what are the signs and symptoms?
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)
Describe the seven named fascia of the proximal upper limb and pectoral region
- Pectoral fascia: invests pec major and is continuous inferiorly with fascia of anterior abdominal wall
- Axillary fascia: as pectoral fascia leaves lateral border of pec major it becomes the axillary fascia, this forms the floor of the axilla
- Clavipectoral fascia: deep to pectoral fascia, descends from clavicle and encloses subclavius and pec minor
- 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
- Supraspinous fascia
- Infraspinous fascia
- 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
Describe in detail the clavipectoral fascia
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)
Which nerve pierces the costocoracoid membrane? What is the function of this nerve?
Lateral pectoral n. (primarily supplying pec major)
Describe the superficial and deep venous drainage of the upper limb
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
What are the two main superficial veins of the upper limb?
Cephalic
Basilic
Median antebrachial
Describe the course of the cephalic vein
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
Describe the course of the basilic vein
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
Describe the course of the median antebrachial vein
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
Where do the deep veins of the upper limb originate?
Superficial and deep venous palmar arches
Where do the superficial lymphatic vessels of the upper limb originate? What is their subsequent course?
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)
