Upper Limb: MRCEM Primary questions with answers

Upper Limb anatomy is one part of the anatomy section of MRCEM Primary, which makes up 60 of the 180 questions. The lessons cover muscles, joints, arterial supply, venous and lymphatic drainage, dermatomes, myotomes and reflexes, and the innervation of the arm, plus other important structures. Examining a shoulder, wrist or hand injury in the emergency department means deciding which nerve or vessel may be at risk.

5 free questions below, each with the answer and the full explanation · 287 in the full bank · Last updated after the 27 October 2026 MRCEM Primary sitting.

1. Question 1 · Innervation of Upper Limb

   A man aged 23 presents with a crush injury to his hand. Which one of the following muscles will remain intact in C8-T1 nerve root injury from high lesions?

   1. AFlexor pollicis longus
   2. BFlexor digiti minimi brevis
   3. CAbductor digiti minimi
   4. DFlexor carpi ulnaris
   5. EFlexor pollicis brevis
   Show answer and explanation

   Answer: A. Flexor pollicis longus is supplied by the anterior interosseous nerve (median), so it is spared in a C8-T1 root injury.

   • B: Supplied by the ulnar nerve (C8-T1), so affected.
   • C: Supplied by the ulnar nerve (C8-T1), so affected.
   • D: Supplied by the ulnar nerve (C8-T1), so affected.
   • E: Supplied by the recurrent median branch (C8, T1), so affected.

   Full explanation: Innervation of Upper Limb

   Brachial Plexus:

   The brachial plexus is a network of nerve fibers that supply the skin and muscles of upper extremity. The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C5, C6, C7, and C8, and the first thoracic spinal nerve, T1. 

   The brachial plexus is divided into five parts

   • Roots
   • Trunks
   • Divisions
   • Cords
   • branches 

   1: Root:

   Formed by the union of anterior rami (divisions) of cervical spinal nerves C5, C6, C7, and C8, and the first thoracic spinal nerve, T1. 

   2: Trunk:

   At the base of the neck, the roots of the brachial plexus converge to form three trunks. 

   • Superior trunk: Combination of C5 and C6 roots. 
   • Middle trunk: Continuation of C7. 
   • Inferior trunk: Combination of C8 and T1 roots 

   3: Division:

   Trunks are divided into anterior and posterior division within posterior triangle of neck. 

   4: Cords:

   Once the anterior and posterior divisions have entered the axilla, they combine together to form three cords 

   • Lateral cord: Anterior division of superior and middle trunk 
   • Medial cord: Anterior division of inferior trunk 
   • Posterior cord: Posterior union of all three trunks 

   5: Branches: 

   BRANCHES OF LATERAL CORD   “LML” 

   • Lateral pectoral nerve 
   • Musculocutaneous nerve 
   • Lateral root of median nerve 

   BRANCHES OF MEDIAL CORD     “M4U” 

   • Medial pectoral nerve
   • Medial cutaneous nerve of arm
   • Medial cutaneous nerve of forearm
   • Medial root of median nerve
   • Ulnar nerve 

    BRANCHES OF POSTERIOR CORD   “ULTRA” 

   • Upper subscapular nerve
   • Lower subscapular nerve 

   Clinical Pearls: 

   Brachial plexus injury: 

   Brachial plexus lesion	Primary deficits	Clinical presentation
   Upper trunk (C5-C6)	Erb-Duchenne palsy (Waiters tip deformity)	Affected arm is adducted and rotated medially The forearm is pronated due to the loss of biceps brachii. The wrist is weakly flexed due to the normal tone of the wrist flexors relative to the weakened wrist extensors. This position is known as ‘waiter’s tip’ and is characteristic of Erb’s palsy.
   Lower trunk (C8-T1)	Klumpke’s palsy (claw hand )	Weakness in hand functions Claw hand deformity: Hyperextension at metacarpophalangeal joint and flexion at inter phalangeal joints

   Axillary Nerve:

   Axillary Nerve is a direct continuation of the posterior cord from the brachial plexus.  

   • Spinal roots: C5 and C6. 
   • Plexus cord: Posterior 
   • Motor functions: Innervates the teres minor and deltoid muscles. 

   • Sensory functions: Gives rise to the upper lateral cutaneous nerve of the arm, which innervates the skin over the lower deltoid (‘regimental badge area’). 

   Note:  Lateral supraclavicular nerve arising from the cervical plexus (C3, C4 ) gives sensory innervation to upper half of deltoid. 

   Anatomical course:

   Axillary nerve arises in the axilla passes medially to the surgical neck of the humerus, where it divides into three terminal branches: 

   • Anterior terminal branch:  winds around the surgical neck of the humerus and provides motor innervation to the anterior aspect of the deltoid muscle. 
   • Posterior terminal branch:  Gives motor innervation to the posterior aspect of the deltoid muscle and teres minor. It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm. 
   • Articular branch: supplies the glenohumeral joint 

   Clinical Pearls: 

   Axillary nerve injury is commonly caused by fracture of surgical neck of humerus or inferior dislocation of humerus. 

   • Causes weak lateral rotation and abduction of the arm. (Supraspinatus can abduct the arm but not to a horizontal level). 
   • Loss of sensation over the inferior portion of the deltoid (the ‘regimental badge area’). 
   • Quadrangular space: Axillary nerve and posterior circumflex humeral artery and vein pass through it and can be compressed as a result of trauma, muscle hypertrophy resulting in weakness of deltoid and teres minor. 

   Median Nerve: 

   Nerve	Median
   Nerve roots	C5 – T1
   Plexus cords	Medial and lateral cords
   Motor Supply	Innervates the flexor and pronator muscles in the anterior compartment of the forearm (except the flexor carpi ulnaris and part of the flexor digitorum profundus, innervated by the ulnar nerve. Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.
   Sensory supply	Gives rise to the palmar cutaneous branch, which innervates the lateral aspect of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.

   After originating from the brachial plexus in the axilla the median nerve descends down the arm, initially lateral to the brachial artery. Halfway down the arm, the nerve crosses over the brachial artery, and becomes situated medially. The median nerve enters the anterior compartment of the forearm via the cubital fossa 

   Branches of Median Nerve in the Forearm 

   Branches of Median Nerve	Origin	Supply
   Median nerve	Axilla	Superficial and intermediate compartment of anterior forearm.
   Anterior interosseous nerve	Forearm	Deep compartment of anterior forearm
   Palmar cutaneous branch	Forearm	Skin over the lateral aspect of the palm

   Branches of Median Nerve in the Hand 

   After giving off the anterior interosseous and palmar cutaneous branches, the median nerve enters the hand via the carpal tunnel where it terminates by dividing into two branches

   Recurrent branch of median nerve	Hand	Thenar muscles (flexor pollicis brevis, abductor pollicis brevis, opponens pollicis)
   Palmar digital branch	Hand	innervates the palmar surface and fingertips of the lateral three and half digits. Also innervates the lateral two lumbrical muscles.

   Clinical Pearls: 

   Carpal tunnel syndrome: Compression of the median nerve within the carpal tunnel can cause carpal tunnel syndrome (CTS). 

   Clinical features: include numbness, tingling, and pain in the distribution of the median nerve. 

   Note: In carpal tunnel syndrome Importantly, the palm is usually spared  as the palmar cutaneous branch does not travel through the carpal tunnel. 

   Lesion	Damaged at elbow	Damaged at wrist
   Mechanisms	Supracondylar fracture of the humerus	Lacerations just proximal to flexor retinaculum
   Motor Loss	The flexors and pronators in the forearm are paralyzed, with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus. The forearm constantly supinated, and weak wrist flexion. Flexion, abduction and opposition of thumb is lost due to paralysis of thenar muscles and flexor digitorum profundus flexion of the index and middle fingers is lost due to paralysis of lateral two lumbricals	Paralysis of thenar muscles and lateral two lumbricals. This affects opposition of the thumb and flexion of the index and middle fingers respectively
   Sensory Loss	Lateral aspect of palm and palmar surface and fingertips of lateral three and a half digits	Palmar surface and fingertips of lateral three and a half digits
   Signs	The thenar eminence is wasted, due to atrophy of the thenar muscles. If patient tries to make a fist, only the little and ring fingers can flex completely. This results in a characteristic shape of the hand, known as hand of benediction.	Thenar eminence wasting

    Note: Flexion of the ring and little fingers at MCPJ and DIPJ are preserved as these are functions of medial half of flexor digitorum profundus and medial two lumbricals innervated by ulnar nerve. 

   Radial Nerve:

   The radial nerve is the terminal continuation of the posterior cord of the brachial plexus 

   Radial nerve arises from the posterior cord and the largest branch of the brachial plexus. 

    The nerve arises in the axilla region, where it is situated posteriorly to the axillary artery, descends posteriorly between the long and medial heads of the triceps, after which it passes inferolaterally with the profunda brachii artery in the spiral (radial) groove on the posterior surface of the humerus between the medial and lateral heads of the triceps. Pierces the lateral intermuscular septum to enter the anterior compartment and descends anterior to the lateral epicondyle between the brachialis and brachioradialis muscles to enter the cubital fossa, where it divides into superficial and deep branches. 

   • Deep branch (motor): innervates the muscles in the posterior compartment of the forearm and continues as posterior interosseous nerve 

   • Superficial branch (sensory): contributes to the cutaneous innervation of the skin of dorsal hand and lateral three and half fingers. 

   Other branches which give cutaneous innervation to skin of upper limb. 

   • Lower lateral cutaneous nerve of arm: Innervates the lateral aspect of the arm, inferior to the insertion of the deltoid muscle. 
   • Posterior cutaneous nerve of arm: Innervates the posterior surface of the arm. 
   • Posterior cutaneous nerve of forearm: Innervates a strip of skin down the middle of the posterior forearm. 

   Clinical Pearls: 

   Radial nerve injury:  

   Wrist Drop: 

   Injury to the radial nerve is commonly caused by a fracture of the midshaft of the humerus. Radial nerve injury results in loss of function in the extensors of the forearm, hand, metacarpals, and phalanges. It also results in the loss of wrist extension, leading to wrist drop, and produces weakness of abduction and adduction of the hand. 

   Note: When the radial nerve is injured in proximal humerus fracture triceps brachii muscle will be affected and patient presents with unable to extend at the forearm. While midshaft of humerus fracture triceps brachii will remain spared

    

   Ulnar Nerve:

   The ulnar nerve arises from the brachial plexus within the axilla region. It is a continuation of the medial cord and contains fibers from spinal roots C8 and T1. 

   Anatomical Course of Ulnar Nerve:

   • Arises from the medial cord of the brachial plexus, runs down the medial aspect of the arm, pierces the medial intermuscular septum at the middle of the arm, and descends together with the superior ulnar collateral branch of the brachial artery. It then Descends behind the medial epicondyle in a tunnel (cubital tunnel), where it is readily palpated and most commonly injured. It may be damaged by a fracture of the medial epicondyle. When irritated, it causes funny bone symptoms of pain, numbness, and tingling in the medial elbow, forearm, and digits.
   • It then enters the forearm by passing between the two heads of the flexor carpi ulnaris and descends between the flexor carpi ulnaris and gives rise to following branches in forearm. 

     Ulnar nerve branches in hand

   • Enters the hand superficial to the flexor retinaculum and lateral to the pisiform bone, where it is vulnerable to damage from cuts or stab wounds and gives rise to following branches in hand. 

   Clinical Pearls: 

   Froment’s sign: Froment’s sign is a test for ulnar nerve palsy specifically paralysis of the adductor pollicis:  

   • Patient is asked to hold a piece of paper between thumb and index finger as paper is pulled away, patient will flex thumb at inter-phalangeal joint to maintain hold, this sign tests the function of adductor pollicis muscle which is supplied by the ulnar nerve. 

   • A positive test is when the patient is unable to adduct the thumb. 

   Claw hand: 

   Injury to the ulnar nerve is commonly caused by a fracture of the medial epicondyle and results in a claw hand, in which the ring and little fingers are hyperextended at the metacarpophalangeal joints and flexed at the interphalangeal joints.  

   • Partial claw hand deformity is due to an isolated ulnar nerve injury. 
   • Complete claw hand deformity: Involves all digits and results from combined ulnar and median nerve injury. 

    

   Ulnar nerve injury at elbow and wrist:

   Lesion	At elbow	At wrist
   Mechanism	Fracture of medial epicondyle	Laceration at wrist
   Motor Loss	All the muscles of innervated by the ulnar nerve are affected. Flexion of the wrist can still occur, but is accompanied by abduction (due to paralysis of flexor carpi ulnaris and medial half of flexor digitorum profundus). Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei). Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles). Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).	Only the intrinsic muscles of the hand are affected. Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei). Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles). Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).
   Sensory Loss	Medial half of palm, palmar and dorsal surface of medial one and a half fingers and medial dorsum of hand	Palmar surface of medial one and a half fingers
   Signs	Froment's sign	Claw hand Froment's sign

   Sensory innervation of Median, Radial and ulnar (High Yield):

    

    Musculocutaneous Nerve: 

   The musculocutaneous nerve is the terminal branch of the lateral cord of the brachial plexus. 

   Nerve roots	C5, C6 & C7
   Plexus cords	Lateral
   Motor Supply	Muscles in Anterior compartment of arm
   Sensory supply	Lateral forearm (via the lateral cutaneous nerve of the forearm)

   Anatomical Course: 

   Musculocutaneous nerve (C5-C7) Pierces the coracobrachialis muscle and descends between the biceps and brachialis muscles. Innervates all of the flexor muscles in the anterior compartment of the arm, such as the coraco- brachialis, biceps, and brachialis muscles. Continues into the forearm as the lateral cutaneous nerve of forearm. 

   Clinical Pearls: 

   • Injury to the musculocutaneous nerve results in weakness of supination (biceps) but can still be performed by the brachioradialis (Innervated by Radial nerve) 
   • Weakness of flexion at the shoulder and elbow but can still be performed by the pectoralis major and brachioradialis respectively and loss of sensation on lateral side of the forearm. 

2. Question 2 · Muscles of the Upper Limb

   A woman aged 55 presents with painful swelling in her hands, especially around the joints, and morning stiffness lasting more than an hour. Clinical examination suggests active synovitis. Which of the following bones/joints of the hand is most commonly involved in synovitis?

   1. AScaphoid bone
   2. BDistal interphalangeal joints
   3. CMetacarpophalangeal joints
   4. DDistal phalanges
   5. ECarpometacarpal joint of the thumb
   Show answer and explanation

   Answer: C. Rheumatoid arthritis classically involves the MCP joints, with swelling and tenderness.

   • A: The scaphoid is a bone, not a joint.
   • B: DIP involvement is typical of osteoarthritis and psoriatic arthritis.
   • D: The distal phalanges are bones, not joints.
   • E: Thumb carpometacarpal involvement is typical of osteoarthritis.

   Full explanation: Muscles of the Upper Limb

   Forearm muscles

   Anterior forearm muscles superficial compartment

    

   Anterior Forearm muscles intermediate compartment: 

   Flexor digitorum superficialis

   Flexes the metacarpophalangeal joints and proximal interphalangeal joints at the 4 fingers, and flexes at the wrist

   Median nerve

    

   Anterior Forearm muscles deep compartment: 

   Flexor pollicis longus	Flexes IPJ and MCPJ of thumb	Median nerve
   Flexor digitorum profundus	Flexes MCPJ and DIPJ of all four digits, flexion of wrist	medial half by ulnar nerve, Lateral half by median nerve.
   Pronator quadratus	Pronation of forearm	Median nerve

    

   Key Point: All the muscles of anterior forearm are innervated by median nerve except flexor carpi ulnaris and medial half of flexor digitorum profundus innervated by ulnar nerve. 

    

   Digital attachment of flexor muscles of forearm: 

   All the anterior forearm muscles originate from the medial humeral epicondyle. 

   Flexor Tendons	Attachment at distal site
   Flexor pollicis longus	Base of distal phalanx of thumb
   Flexor digitorum profundus	Distal phalanges of all four digits
   Flexor digitorum superficialis	Middle phalanges of all four digits
   Flexor carpi ulnaris	Pisiform, hook of hamate and 5th metacarpal
   Flexor carpi radialis	Base of 2nd and 3rd metacarpal
   Palmaris longus	Palmar aponeurosis

    

   Muscles of Anterior Arm:

   Muscle	Function	Innervation
   Biceps brachii	Flexion and supination of forearm Flex arm at elbow and at shoulder	Musculocutaneous nerve
   Coracobrachialis	Flexion of arm at shoulder and assist in weak adduction	Musculocutaneous nerve
   Brachialis	Flexion of forearm at elbow	Musculocutaneous nerve

    

    

   Muscles of posterior Arm:

   Triceps brachii: 

   Triceps brachii is a large thick muscle in the posterior arm and appears as a horseshoe-shaped muscle 

   Function:  Extension of forearm at elbow and extension of arm at shoulder joint. 

   Innervation: Radial nerve 

    

   Muscles of posterior forearm 

   The muscles in the posterior compartment of the forearm are commonly known as the extensor muscles. 

   Extensor muscles are divided into superficial and deep compartment. 

   Superficial compartment:

   Muscle	Function	Innervation
   Brachioradialis	Flexes forearm at elbow	Radial nerve
   Extensor carpi radialis longus	Extension and abduction of wrist	Radial nerve
   Extensor carpi radialis brevis	Extension and abduction of wrist	Radial nerve
   Extensor digitorum	Extension of all four fingers, extension of wrist	Radial nerve
   Extensor digiti minimi	Extension of little finger	Radial nerve
   Extensor carpi ulnaris	Extension and adduction of wrist	Radial nerve
   Anconeus	Extension and stabilize elbow. Abducts the ulna during pronation of the forearm.	Radial nerve

    

   Deep Compartment:

   Muscle	Function	Innervation
   Supinator	Supinates forearm.	Radial nerve
   Abductor pollicis longus	Abduction and extension of thumb	Radial nerve
   Extensor pollicis longus	Extension of distal phalanx of thumb	Radial nerve
   Extensor pollicis brevis	Extension of proximal phalanx of thumb	Radial nerve
   Extensor indicis	Extension of index finger	Radial nerve

   Clinical pearl: 

   1: Tennis elbow (lateral epicondylitis): is caused by a chronic inflammation or irritation of the origin of the extensor muscles of the forearm from the lateral epicondyle of the humerus as a result of repetitive strain. It is a painful condition and common in tennis players.  

   2: Golfer’s elbow (medial epicondylitis):  is a painful condition caused by a tear or chronic inflammation in the origin of flexor muscles of the forearm 

   3: Nursemaid’s elbow or pulled elbow is a radial head subluxation and occurs in toddlers when the child is lifted by the wrist. The annular ligament (and other elbow ligaments) is not fully developed in terms of strength, and thus, the radial head can slip out of position. 

    

   Muscles of the hand: 

   Thenar muscles:

   Three short muscles located in the base of the thumb. All are innervated by median nerve. 

    

   Hypothenar muscles:

   Hypothenar muscle located at base of middle finger and form hypothenar eminence. All are innervated by ulnar nerve 

    

   Lumbrical Muscles: 

   There are four lumbrical muscles. Each one of these originates from a tendon of the flexor digitorum profundus. They pass dorsally and laterally around each finger, and inserts into the extensor hood. 

   Innervation:  

   Medial two lumbricals: Ulnar nerve 

   Lateral two lumbricals: Median nerve 

    

   Function:

   Flexion at the MCP joint and extension at the interphalangeal (IP) joints of each digit.

    

   Clinical pearls:

   Denervation of these muscles is the basis of claw hand and hand of benediction. 

    

   Interossei muscles: Located between the metacarpals of the hand. Divided into Dorsal and palmar Interossei 

   All the interossei muscles are innervated by ulnar nerve. 

   Dorsal Interossei: 

   Abduction of the digits. Assists in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints. 

   Palmar Interossei:  

   Adduction of the digits. Assists in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints. 

    

   Muscles of the Shoulder region:

   Extrinsic muscles, Intrinsic Muscles 

   Extrinsic muscles: Connecting the Upper Limb to the Vertebral Column and divided into superficial and deep group. 

   Superficial: Trapezius and Latissimus dorsi 

   Deep: Levator Scapulae, Rhomboid minor and Rhomboid major

    

      

    

   Clinical pearl: Ask the patient to shrug his/her shoulder if patient unable to do this indicates spinal accessory nerve injury and paralysis of trapezius muscle. 

    

   Intrinsic muscles of the shoulder: Connecting the scapula to the humerus 

   There are six muscles in this group the deltoid, teres major, and the four rotator cuff muscles (supraspinatus, infraspinatus, subscapularis and teres minor). 

    

   MUSCLE	NERVE SUPPLY	NERVE ROOT	FUNCTION
   Deltoid	Axillary nerve	C5, 6	Abducts arm; anterior fibers flex and medially rotate arm; posterior fibers extend and laterally rotate arm.
   Teres Major	Lower subscapular nerve	C6, C7	Medially rotates and adducts. arm and stabilizes shoulder.
   Supraspinatus	Suprascapular nerve	C4, 5, 6	Abducts arm to initial 15 degree and stabilizes. shoulder joint
   Infraspinatus	Suprascapular nerve	(C4), 5, 6	Laterally rotates arm and stabilizes shoulder joint.
   Teres minor	Axillary nerve	(C4), C5, 6	Laterally rotates arm and stabilizes shoulder joint
   Subscapularis	Upper and lower Subscapular nerves: branches of brachial plexus	C5, 6, 7	Medially rotates arm and stabilizes shoulder joint.

    

   Note: All the rotator cuff muscles (SITS) are lateral rotators of arm except “S” Subscapularis  

    

   Clinical pearl:

   Assessment of rotator cuff muscles:

   Supraspinatus	Empty Can test: In this test, the patient is tested at 90 degrees elevation in the scapular plane and full internal rotation and pronation of the forearm with thumbs pointing downwards the patient resists downward pressure exerted by the examiner at the patients elbow or wrist.
   Infraspinatus	Infraspinatus test: Patient arm fully adducted with elbow flexed to 90 degrees. The examiner will apply an internal rotation force along the patient’s forearm while the patient resists. The test is positive if the patient experiences pain or weakness.
   Teres minor	Hornblower test: The examiner places the patient's arm to 90oin the scapular plane and flexes the elbow to 90o. The patient is then asked to externally rotate against resistance. The test is positive if the patient is unable to perform external rotation.
   Subscapularis	Lift off test: Position the patient in full medial rotation with the dorsum of the hand on the lower back. Ask the patient to lift their hand away from their back against resistance. Test is positive if patient has pain or weakness.

    

    

   Rotator cuff tendonitis:

   • Refers to inflammation of tendons of rotator cuff muscles. 
   • Supraspinatus is the most commonly injured rotator cuff muscle.

    

    

   Muscles of pectoral region:

   Pectoralis Major: large fan shaped and most superficial muscle of the pectoral region. 

   Origin: 

   • Clavicular head: Medial clavicle 
   • Sternocostal head originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle. 

   Insertion: intertubercular sulcus of the humerus 

   Function: Adduction and medial rotation of the upper limb and draws the scapula Antero inferiorly. 

   Innervation: Lateral and medial pectoral nerves 

    

   Pectoralis minor: small muscle lies underneath the pectoralis major. 

   Origin: Originates from the 3rd-5th ribs   

   Insertion: coracoid process of the scapula 

   Function: stabilization, depression, abduction or protraction, internal rotation and downward rotation of the scapula. 

   Innervation: Medial pectoral nerve 

    

   Serratus anterior: Located more laterally in the chest wall 

   Origin: Consists of several muscular strips originate from lateral surface of ribs 1-8 

   Insertion: Attach to the costal surface of medial border of scapula 

   Function: holds the scapula against the ribcage and assist in protraction and rotation of scapula 

   Innervation: Long thoracic nerve

    

   Clinical pearl: 

   winging of scapula: Scapula no longer held against the rib cage and protrudes out of the back due to paralysis of serratus anterior and injury to Long thoracic nerve. 

    

   Subclavius: Small muscle located underneath the clavicle 

   Origin: First rib and its costal cartilage 

   Insertion: Inferior surface of middle third of clavicle 

   Function: Anchors and depresses clavicle 

   Innervation: Nerve to subclavius.

    

    

    

3. Question 3 · Upper Limb Other Important Structures

   A patient attends with carpal tunnel syndrome. Which of the following is the most lateral structure in the carpal tunnel:

   1. AMedian nerve
   2. BFlexor digitorum profundus tendons
   3. CFlexor pollicis longus tendon
   4. DFlexor digitorum superficialis tendons
   5. ERadial artery
   Show answer and explanation

   Answer: C. Flexor pollicis longus tendon is the most lateral structure in the carpal tunnel.

   • A: The median nerve lies medial to FPL, anterior to the FDS tendons.
   • B: FDP tendons lie deep and medial to FPL.
   • D: FDS tendons lie superficial and medial to FPL.
   • E: The radial artery does not pass through the carpal tunnel.

   Full explanation: Upper Limb Other Important Structures

   Carpal Tunnel:

   The carpel tunnel is the space that lies between the flexor retinaculum. 

   Contents of the carpal tunnel 

   Roof	Flexor retinaculum
   Carpal arch	Medially: Pisiform and hook of the hamate Laterally: tubercles of the scaphoid and trapezium
   Contents	Four tendons of flexor digitorum profundus (FDP) Four tendons of flexor digitorum superficialis (FDS): Most superficial structure (Recall) Tendon of flexor pollicis longus (FPL): Lateral structure (Recall) median nerve laterally

    Note: 

   •  The ulnar nerve, ulnar artery and tendon of Palmaris longus runs superficial to flexor retinaculum and thus are not within carpel tunnel. 
   • Flexor pollicis longus enter the carpel tunnel before reaching its insertion on the distal phalanx of the thumb. 
   • Pronator quadratus is confined to the distal forearm and does not reach the carpel tunnel. 

   Anatomical snuffbox

   • is a triangular depression found on the lateral aspect of the dorsum of the hand. It is best seen when the thumb is extended. 

   Clinical Pearl: 

   Fracture of scaphoid bone: Falling on outstretched hand. The scaphoid bone of the hand is the most commonly fractured carpal bone 

    Clinical feature: Pain and tenderness in the anatomical snuffbox. 

   Ulnar canal (Guyon’s canal)

   • Transmits ulnar neurovascular bundle from forearm into the hand.

   Borders:

   • Medial (ulnar): pisiform, flexor carpi ulnaris tendon
   • Lateral (radial): hook of hamate.
   • Roof: palmar carpal ligament.
   • Floor: flexor retinaculum

   Contents: Ulnar nerve and artery

   Clinical Pearl: 

   • Ulnar canal syndrome refers to compression of the ulnar nerve within the ulnar canal. 

   Flexor Retinaculum:

   The flexor retinaculum is a thickened band of fibrous connective tissue on the volar aspect of the hand which forms the roof of the carpal tunnel. The flexor retinaculum holds the flexor tendons in place at the wrist and prevents them from bowstringing. 

   Relations of flexor retinaculum: 

   • The ulnar artery, ulnar nerve, tendon of the palmaris longus and palmar cutaneous branch of the median nerve pass into the hand anterior to the flexor retinaculum, and therefore do not pass through the carpal tunnel.
   • The flexor carpi radialis tendon passes through the lateral aspect of the flexor retinaculum into the hand.
   • The four tendons of the flexor digitorum profundus, the four tendons of the flexor digitorum superficialis, the tendon of the flexor pollicis longus and the median nerve pass into the hand posterior to the flexor retinaculum, within the carpal tunnel. 

   Extensor Retinaculum: 

   The extensor retinaculum lies obliquely across the extensor surface of the wrist joint, thickened part of the antecubital fossa and that holds the extensor tendons in place during movement of the wrist. 

   Attachments: 

    Laterally: Lower part of the anterior border of the radius 

    Medially: Styloid process of the ulna, Triquetral, and Pisiform 

   Contents 

   The extensor tendons pass through the extensor tunnel, deep to the extensor retinaculum, in six compartments lined by synovial sheaths: 

   • The tendons of the extensor carpi ulnaris and extensor digiti minimi have separate sheaths on the medial side of the wrist. 
   • The tendons of the extensor digitorum and extensor indicis share a synovial sheath on the posterior surface of the wrist. 
   • The tendons of the abductor pollicis longus and extensor pollicis brevis, the extensor carpi radialis longus and extensor carpi radialis brevis, and the extensor pollicis longus have three separate sheaths on the lateral side of the wrist.   

   Other Clinical High Yield Stuff: 

   1: Dupuytren contracture: is a progressive thickening, shortening, and fibrosis of the palmar fascia. producing a fixed flexion contracture of the hand, in which the fingers bend toward the palm and cannot be fully extended (commonly fourth and fifth fingers). 

   2: Volkmann contracture: is an ischemic contracture (flexion deformity) resulting from necrosis of the forearm flexor muscles. 

   3: Tenosynovitis:  is commonly caused by an infection of the synovial sheath and tendon (the long flexor tendon), causing pain, swelling, and difficulty moving a joint. Rupture of the tendon sheath (puncture injury of the palm) may cause the spread of infection to the mid-palmar space and to the carpal tunnel. Likewise, tenosynovitis in the thumb may spread to the radial bursa and in the little finger to the ulnar bursa. 

   Note: Infection in the middle three fingers is usually contained as they have separate synovial sheaths. 

   • The synovial sheath of the little finger is usually continuous with the common flexor sheath (the ulnar bursa) and thus infection may spread to this sheath and from here to the mid-palmar space. 
   • Infections in the thumb may spread to the mid-palmar space via the continuous synovial sheath of the flexor pollicis longus (the radial bursa).   

   4: Trigger finger: occurs when the long flexor tendon develops a nodule or swelling that interferes with its gliding through the pulley, causing pain at the joint and an audible clicking or snapping. The condition is caused by rheumatoid arthritis, repetitive trauma, and wear and tear of aging of the tendon. 

   5: Mallet finger (hammer finger or baseball finger) is a finger with permanent flexion of the distal phalanx as a result of an avulsion of the lateral bands of the extensor tendon to the distal phalanx. 

   6:  Boutonniere deformity is a finger with abnormal flexion of the middle phalanx and hyperextension of the distal phalanx as a result of a rupture of the central band of the extensor tendon 

   7:  Pancoast tumor in the apex of the lung can result in lower trunk injury and, occasionally, Horner syndrome because of sympathetic ganglion compression (ptosis, anhidrosis, and pupillary constriction). It can also cause thoracic outlet syndrome. 

    

4. Question 4 · Upper Limb

   You are examining the shoulder of a 20 year old football player who reports pain after a collision during an aerial challenge for the ball. You note he is tender over a focal area of his proximal trapezius muscle. From which of the following structures does the trapezius muscle originate:

   1. AThe parietal bone and the spinous processes of C5 - T5
   2. BThe occipital bone and the spinous processes of C2 - C7
   3. CThe ligamentum nuchae and the spinous process of C2 - C7.
   4. DThe spinous processes of C1 - T12
   5. EThe occipital bone, the ligamentum nuchae and the spinous processes of C7 - T12
   Show answer and explanation

   Answer: E. Trapezius arises from the occiput, ligamentum nuchae and spinous processes of C7-T12.

   • A: Origin is the occipital, not parietal, bone and extends to T12.
   • B: Origin extends below C7 to T12, not just C2-C7.
   • C: Origin also includes the occiput and extends to T12.
   • D: It does not arise from all spinous processes from C1; above C7 it arises from the occiput and ligamentum nuchae.

   Full explanation: Trapezius Muscle

   The trapezius muscle is responsible for the smooth contour of the lateral side of the neck and over the superior aspect of the shoulder.

   Table: Function and Innervation of the Trapezius Muscle

   Muscle	Trapezius
   Origin	Superior nuchal line, external occipital protuberance, medial margin of ligamentum nuchae, spinous processes of C7 – T12 and the related supraspinous ligaments
   Insertion	Superior edge of crest of the spine of the scapula, acromion and posterior border of lateral one-third of clavicle
   Function	Elevation of scapula, rotation of scapula during abduction of humerus above horizontal, retraction and depression of scapula
   Innervation	Spinal accessory nerve

   Origin

   The trapezius muscle has an extensive origin from the axial skeleton, originating from the superior nuchal line, the external occipital protuberance, the medial margin of the ligamentum nuchae, the spinous processes of C7 - T12 and the related supraspinous ligaments.

   Insertion

   The muscle inserts onto the skeletal framework of the shoulder (to the superior edge of the crest of the spine of the scapula, the acromion and the posterior border of the lateral one-third of the clavicle) along the inner margins of a continuous U-shaped line of attachment orientated in the horizontal plane, with the bottom of the U directed laterally.

   Function

   The trapezius is a powerful elevator of the shoulder and also rotates the scapula to extend the reach superiorly (during abduction of the humerus above horizontal). The middle fibres retract the scapula and the lower fibres depress the scapula.

   Innervation

   The trapezius is innervated by the spinal part of the accessory nerve (motor supply) and the anterior rami of C3 and C4 (sensory supply). These nerves pass vertically along the deep surface of the muscle. The accessory nerve can be evaluated by testing the function of the trapezius muscle, most easily done by asking the patient to shrug their shoulders against resistance.

   Trapezius Muscle. (Image by Mikael Häggström, used with permission. (Image:Gray409.png) [Public domain or Public domain], via Wikimedia Commons)

5. Question 5 · Joints of the Upper Limb

   A 43 year old tree surgeon is brought to the ED after falling approximately 10 metres from a tree. During assessment of the C-spine he has pain on palpation of C4/5. At which of the following landmarks is the C4 dermatome best tested:

   1. AAt the apex of the axilla
   2. BIn the supraclavicular fossa at the midclavicular line
   3. COver the greater tuberosity of the humerus
   4. DOver the coracoid process
   5. EOver the acromioclavicular joint
   Show answer and explanation

   Answer: E. The C4 dermatome is tested over the acromioclavicular joint.

   • A: The apex of the axilla tests T2.
   • B: The supraclavicular fossa tests C3.
   • C: The greater tuberosity is not the C4 test site.
   • D: The coracoid process is not the C4 test site.

   Full explanation: Dermatomal Supply of Upper Limb

   Table: Dermatomal Supply of the Upper Limb

   Dermatome	Landmark
   C2	Occipital Protuberance
   C3	Supraclavicular Fossa
   C4	Acromioclavicular Joint
   C5	Lateral Antecubital Fossa
   C6	Thumb
   C7	Middle Finger
   C8	Little Finger
   T1	Medial Antecubital Fossa
   T2	Apex of Axilla

   Dermatome Map. (Image by Grant, John Charles Boileau (An atlas of anatomy, / by regions 1962) [Public domain], via Wikimedia Commons)

   The C2 dermatome is best tested at least one cm lateral to the occipital protuberance at the base of the skull. Alternately, it can be located at least 3 cm behind the ear.

   The C3 dermatome is best tested in the supraclavicular fossa, at the midclavicular line.

   The C4 dermatome is best tested over the acromioclavicular joint.

   The C5 dermatome is best tested on the lateral (radial) side of the antecubital fossa just proximal to the elbow.

   The C6 dermatome is best tested on the dorsal surface of the proximal phalanx of the thumb.

   The C7 dermatome is best tested on the dorsal surface of the proximal phalanx of the middle finger.

   The C8 dermatome is best tested on the dorsal surface of the proximal phalanx of the little finger.

   The T1 dermatome is best tested on the medial (ulnar) side of the antecubital fossa, just proximal to the medial epicondyle of the humerus.

   The T2 dermatome is best tested at the apex of the axilla.