Station 1: neurovasculature of limbs Flashcards
Where does the subclavian artery become the axillary artery?
Lateral edge of rib 1 and enter into the axilla
Where does the axillary artery become the brachial artery?
Inferior margin of teres major muscle
Where does the brachial artery bifurcate into the radial and ulnar nerve?
Apex of cubital fossa at level of radial neck, underneath the brachialis muscle
What relation is the brachial artery to the tendon of biceps brachii?
Medial
Where is the median nerve in relation to the brachial artery?
Medial and anterior
Which is usually larger, the ulnar or radial artery?
Ulnar
Where are the radial and ulnar arteries located? What are the anatomical relations?
Forearm
Radial is lateral
Ulnar is medial
How are the radial and ulnar arteries injured?
What structures may also be injured?
Radial/ulnar fractures
Slitting of wrist
Where does the right subclavian artery arise from?
Brachiocephalic trunk
Where does the left subclavian artery arise?
Directly off the arch of the aorta
What could an axillary artery aneurysm compress?
The brachial plexus leading to neurological symptoms such as paraesthesia and muscle weakness
When could an axillary artery aneurysm occur?
As a result of atherosclerosis, thoracic outlet syndrome or trauma
If the brachial artery was completely blocked or severed, what would happen?
This causes a characteristic flexion deformity called Volkmann’s contracture.
Caused by: resulting ischaemia of the forearm can cause necrosis and paralysis of the muscles in the forearm. The affected muscles are replaced by scar tissue and shorten considerably.
Which part of the forearm does the radial artery supply?
The posterior aspect
Which part of the forearm does the ulnar artery supply?
The anterior aspect
What are the common sites for compression of the arteries of the upper limb to prevent haemorrhaging?
Subclavian artery:
At the 1st rib - downward pressure in angle between clavicle and inferior attachment of SCM
Axillary artery:
inferior part of lateral wall of axilla, compress against the humerus
Brachial artery:
compression against the medial humerus
What is the route of the basilic vein?
Originates from the dorsal venous network of the hand -> medial aspect of upper limb -> borders teres major -> moves deep into arm and combines with brachial vein to form the axillary vein
What is the route of the cephalic vein?
Originates from the dorsal venous network of the hand -> antero-lateral aspect of the upper limb, passing anteriorly at the elbow -> travels in the deltopectoral groove at the shoulder (between deltoid and pec major) -> enters axilla region via clavipectoral triangle -> in the axilla, cephalic vein terminates by joining the axillary vein
Which vein passes through the anatomical snuffbox?
Cephalic vein
Where do the cephalic and basilic vein connect? What is this vein called and what is commonly used for?
At the elbow, anteriorly at the cubital fossa, they are connected by the median cubital vein.
Commonly used for venipunctures.
What type of veins are the cephalic and basilic vein?
Superficial
Which spinal nerves make up the brachial plexus?
Anterior rami (divisions) of the cervical spinal nerves: C5, C6, C7, C8 and first thoracic spinal nerve T1
What is the brachial plexus divided up into?
Rugby Twats Drink Cold Beer
Roots, trunks, divisions, cords, branches
What are the roots of the brachial plexus?
C5, C6, C7, C8, T1 (anterior divisions)
How do the spinal nerves leave the spinal cord?
At each vertebral level, paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column.
Each nerve divides into the anterior and posterior nerve fibres. The roots of the brachial plexus are formed by the anterior divisions of the spinal nerves.
The posterior divisions go on to innervate the skin and musculature of the trunk.
The nerves then pass between the anterior and medial scalene muscles to enter the base of the neck.
How are the trunks formed?
At the base of the neck, the roots converge forming three trunks:
Superior trunk - C5,C6 roots
Middle trunk - C7 root
Inferior trunk - C8, T1 roots
The trunks move laterally, crossing the posterior triangle of the neck
How are the divisions formed?
Each trunk divides into two divisions. One anteriorly and the other posteriorly, in relation to the mid clavicle.
The anterior divisions supply anterior compartment (flexors) and posterior divisions supply posterior compartment (extensors).
They leave the posterior triangle and pass into the axilla region.
How are the cords formed?
Once in the axilla, the divisions combine to form three cords. These are named due to their relation to the second part of the axillary artery.
How is the lateral cord formed?
Anterior division superior trunk
Anterior middle trunk
How is the posterior cord formed?
Posterior division of the superior trunk
Posterior division of the middle trunk
Posterior division of the inferior trunk
How is the medial cord formed?
The anterior division of the inferior trunk
The cords give rise to which major branches of the brachial plexus?
Musculocutaneous nerve Median nerve Ulnar nerve Axillary nerve Radial nerve
Which nerve roots and cord supply the musculocutaneous nerve?
C5,C6,C7
Lateral cord
What are the motor functions of the musculocutaneous nerve?
Muscles of anterior compartment: coracobrachialis, biceps brachii, brachialis (BBC)
Flexion of upper arm at shoulder and elbow, supination of forearm (biceps)
What are the sensory functions of the musculocutaneous nerve?
Gives rise to lateral cutaneous nerve of the forearm - innervates skin of the lateral surface of the forearm
Where is the musculocutaneous nerve commonly injured?
Uncommon, well protected within the axilla
Most common - stab wound to the axilla region
What motor functions are affected in a musculocutaneous nerve injury?
BBC muscles
Flexion at shoulder is weakened (pec major)
Flexion at the elbow affected (brachioradialis)
Supination weakened (supinator muscle)
What sensory functions are affected in a musculocutaneous nerve injury?
Loss of sensation over anterolateral side of the forearm
Which nerve roots and cord supply the axillary nerve?
C5, C6
Posterior cord
What are the motor functions of the axillary nerve?
Innervates teres minor (stabilises glenohumeral joint, externally rotates upper limb) and deltoid muscles (abduction of upper limb)
What are the sensory functions of the axillary nerve?
Give rises to superior lateral cutaneous nerve of arm, innervates skin of inferior deltoid (regimental badge)
Where is the axillary nerve most commonly damaged?
Trauma to shoulder or proximal humerus - such as fracture of humerus surgical neck, shoulder dislocation
What motor functions are affected in a axillary nerve injury?
Paralysis deltoid and teres minor muscles - renders patient unable to adbuct the affected limb
What sensory functions are affected in a axillary nerve injury?
Upper lateral cutaneous nerve of arm, resulting in loss of sensation over the regimental badge arm.
What are the characteristic clinical signs of axillary injury?
Paralysed deltoid muscle rapidly atrophies, the greater tuberosity can be palpated in that area
What are the roots of the median nerve?
C6 - T1 (some indiv have C5 fibres too)
From medial and lateral cords
What are the motor functions of median nerve?
Flexor muscles in the anterior compartment of the forearm (except flexor carpi ulnaris and medial half of the flexor digitorum profundus)
Thenar muscles
Lateral two lumbricals in hand
What are the sensory functions of the median nerve?
Give rise to palmar cutaneous branch ->
Lateral part of palm
Digital cutaneous branch -> lateral three and a half fingers on anterior/palmar surface of the hand
How is the median nerve commonly injured?
Supracondylar fracture of the humerus (damage at the elbow)
Laceration just proximal to flexor retinaculum (damage at the wrist)
What are the motor deficits when the median nerve is damaged at the elbow?
Flexors and pronators of forearm paralysed
= forearm constantly supinated and flexion is weak
Flexion of thumb prevented
Lateral two lumbricals affected - won’t be able to flex at MCP joints or extend at IP joints of index and middle fingers
What are the sensory deficits when the median nerve is damaged at the elbow/wrist?
Lack of sensation over the areas that the median nerve innervates - lateral part of palm, lateral three and a half fingers on palmar aspect of hand
What are the motor deficits when the median nerve is damaged at the wrist?
Thenar muscles and lateral two lumbricals are paralysed
Affects opposition of the thumb and flexion of the index and middle fingers
Characteristic signs of median nerve damage
Thenar eminence wasted
Pt makes a fist -> little and ring fingers flex = shape of ‘hand of benediction’
What are the roots of the radial nerve?
C5-T1
Posterior cord
What is the sensory supply of the radial nerve?
Skin of posterior side of forearm, dorsal surface of lateral side of palm, lateral three and a half digits
What is the motor supply of the radial nerve?
Triceps brachii (extends at elbow) Majority of extensor muscles in the forearm (extends wrist and fingers and supinates forearm)
How is the radial nerve damaged in the axilla region?
Dislocation at the shoulder joint
Fracture of the proximal humerus
What are the motor and sensory deficits of damage to the radial nerve in the axilla?
Triceps, posterior compartment of forearm- unable to extend forearm, wrist and fingers
Unopposed flexion of wrist = wrist-drop
Loss of sensation over lateral and posterior upper arm, posterior forearm, dorsal surface of lateral 3.5 digits
How is the radial nerve damaged in the radial groove?
Fracture of humeral shaft
What are the motor and sensory deficits of damage to the radial nerve in the spiral groove?
Triceps weakened
Posterior forearm = wrist drop
Loss of sensation to dorsal surface of lateral 3.5 digits, associated palm area
What are the MOI to damage to the radial nerve in the forearm and what would be the associated motor/sensory deficit?)
Stabbing/laceration to the forearm:
No motor, sensory loss of lateral 3.5 and palm dorsally
Fracture of radial head or posterior dislocation of radius:
Posterior forearm muscles, wrist drop doesn’t occur as extensor carpi radialis longus is unaffected and maintains some extension at the wrist
No sensory deficit
What are the roots are the ulnar nerve?
C8, T1
Medial cord
What are the motor functions of the ulnar nerve?
Muscles of the hand (except thenar muscles and two lateral lumbricals), flexor carpi ulnaris, medial half of flexor digitorum profundus
What is the sensory innervation of the ulnar nerve?
Anterior and posterior surfaces of the medial one and half fingers, associated palm area
Where is the ulnar nerve susceptible to injury?
Elbow and wrist
How is the ulnar nerve commonly damaged at the elbow?
Medial epicondyle injury - such as a fracture
What are the motor and sensory deficits when the ulnar nerve is damaged at the medial epicondyle?
Flexor carpi ulnaris and medial half of flexor digitorum profundus paralysed -> flexion of wrist can occur but is accompanied by abduction
Abduction and adduction of fingers can’t occur
Movement of little and ring fingers greatly reduced
Loss of sensation in anterior and posterior surfaces of the medial one and half fingers, associated palm area
Patient can’t grip paper placed between fingers
What are the motor and sensory deficits when the ulnar nerve is damaged by laceration of the wrist?
Abduction and adduction can’t occur
Movement of little and ring finger reduced but muscles in forearm are unaffected
Just the palmar branch and superficial branch affected so sensory loss over palmar medial 1.5 fingers
Patient can’t grip paper and ulnar claw develops over long term
What is ulnar claw?
Hyperextension of MCP joints of little and ring fingers (paralysis of lumbricals)
Flexion at ITP joins
What is a upper brachial plexus injury? (Erb’s palsy/waiter’s tip)
Excessive increase in angle between neck and shoulder (stretch or tear of superior nerve roots) -> difficult birth of shoulder trauma
Nerves derived from C5 or C6 solely
Affected limb hangs limp, medially rotated, pronated
What is a lower brachial plexus injury? (klumpke’s palsy/claw hand)
Excessive abduction of arm - person catching a branch when fall from tree
Nerves derived from T1 - median and ulnar
-> clawed hand appearance
What is the function of anterior compartment of the forearm?
Flexion at wrist and fingers
Pronation
Innervated by ulnar and median nerve
What is the function of the posterior compartment of the forearm?
Extension at the wrist and fingers
Supination
Innervated by the radial nerve
What is the blood supply to the anterior compartment of the forearm?
Ulnar and radial artery
What is the blood supply to the posterior compartment of the forearm?
Anterior and posterior interosseous arteries (branches of short common interosseous artery from the proximal artery)
Why is compartment syndrome more common in the anterior compartment of the forearm?
Me don’t know
