Anatomy of the Upper Limbs

Question 1

Which neck of the humerus is more commonly damaged? The surgical neck or the anatomical neck?

Answer 1

The surgical neck is more commonly damaged.

Question 2

What are the compartments of the shoulder and arm region?

Answer 2

There are 5 compartments in this region.
Anterior and posterior pectoral girdle muscles.
Intrinsic shoulder muscles
Anterior and posterior compartments of the arm.

Question 3

Which muscles comprise the anterior pectoral girdle muscles?

Answer 3

Pectoralis major and minor, subclavius and serratus anterior.
N.B. the serratus anterior runs between the anterior and posterior pectoral girdle compartments.

Question 4

Describe the pectoralis major muscle.

Answer 4

Medial attachment is the medial 1/3 of the clavicle, sternum and costal cartilages.
Lateral attachment is the lateral lip of the intertubercular sulcus.
Action: adducts and medially rotates the humerus.

Question 5

Describe the pectoralis minor muscle.

Answer 5

Lies deep to pectoralis major.
Medial attachment is anterior surface of ribs 2-5.
Lateral attachment is coracoid process of scapula.
Protracts and depresses scapula.

Question 6

Describe the action of the subclavius.

Answer 6

Anchors the clavicle to the 1st rib.

Question 7

Describe the serratus anterior muscle.

Answer 7

Runs from medial border of scapula to the anterior attachments of the ribs.
Supplied by long thoracic nerve.
Protracts medial border of scapula. Rotates scapula upward by laterally rotating inferior angle.

Question 8

Which muscles form the posterior pectoral girdle muscle compartment?

Answer 8

Trapezius, latissimus dorsi, levator scapulae and the rhomboids.

Question 9

Describe the trapezius muscle.

Answer 9

Attaches ligamentum nuchae and spinous processes (to T12) to the spine of the scapula, acromion and clavicle.
Innervated by accessory nerve (CNXI) - N.B. this upper limb muscle is innervated by a cranial nerve.
Has major actions on the scapula.
Has ascending and descending parts.

Question 10

Describe the latissimus dorsi.

Answer 10

Medial attachment is the thoracolumbar fascia (T8 and below).
Lateral attachment is the floor of the intertubercular groove of humerus.
Supplied by thoracodorsal nerve.
Extends, adducts and rotates humerus. Important in rowing and climbing.

Question 11

Describe the levator scapulae.

Answer 11

Medial attachments are the transverse processes of C1-4.
Lateral attachment is superior angle of scapula.
Elevate and rotate scapula.
Supplied by dorsal scapular nerve.

Question 12

Describe the rhomboids.

Answer 12

Medial attachments are the spinous processes of C7-T5.
Lateral attachment is the medial border of the scapula.
Retracts, rotates and fixes scapula.
Supplied by dorsal scapular nerve.

Question 13

Which muscles comprise the intrinsic shoulder muscles?

Answer 13

Deltoid, teres major and rotator cuff muscles.

Question 14

Which muscles form the rotator cuff muscles, and what is the role of this group?

Answer 14

Supraspinatus, infraspinatus, teres minor and subscapularis.
These work together to fix the head of the humerus in the glenoid fossa. The supraspinatus is important in initiating abduction of the arm for the first 15 degrees, then the deltoid takes over.
The supraspinatus, infraspinatus and teres minor fix the humerus superoposterioly and the subscapularis stabilises it anteriorly, meaning the main direction of dislocation is inferiorly.
The supraspinatus inserts into the superior facet on the greater tubercle; the infraspinatus into the middle facet and the teres minor into the inferior facet.
Subscapularis inserts into lesser tubercle. Medial rotation.

Question 15

Describe the deltoid muscle.

Answer 15

Proximal attachment is acromion of scapula.
Distal attachment is deltoid tuberosity of humerus.
Supplied by axillary nerve.
Abducts arm.

Question 16

Describe the action, attachments and innervation of the teres major muscle.

Answer 16

Action: adducts and medially rotates arm.
Innervated by lower subscapular nerve.
Medially attached to the dorsal surface of the inferior angle of the scapula.
Laterally attached to the medial lip of the intertubercular sulcus.

Question 17

Which muscles comprise the anterior compartment of the arm? Which nerve supplies all of these?

Answer 17

Biceps, brachialis and coracobrachialis.

All supplied by musculocutaneous nerve.

Question 18

Describe the biceps (biceps brachii).

Answer 18

The biceps has 2 heads.
The common distal attachment is the radial tuberosity as the biceps tendon. Also becomes biceps aponeurosis and blends with fascia.
The short head’s proximal attachment is the coracoid process.
The long head’s proximal attachment is the supraglenoid tubercle. It runs through the intertubercular sulcus.

Question 19

Give the attachments of the coracobrachialis and brachialis muscles.

Answer 19

Coracobrachialis:
Proximal = coracoid process.
Distal = shaft of humerus.
Flexes ARM.

Brachialis: proximal is the shaft of humerus, distal is the coronoid process of ulna.
Flexes FOREARM.

Question 20

Which muscles comprise the posterior compartment of the arm and which nerve supplies them?

Answer 20

Triceps and anconeus, supplied by radial nerve.

Question 21

Describe the anconeus muscle.

Answer 21

Proximal attachment is the lateral epicondyle of the humerus.
Distal attachment is the shaft of the ulna.

Question 22

Describe the triceps (triceps brachii).

Answer 22

Distal attachment is the olecranon process of the ulna, as the triceps tendon.
Proximal attachments: lateral and medial heads attach to the shaft of the humerus.
The long head attaches to the infraglenoid tubercle of the scapula.

Question 23

Which joints are present in the pectoral girdle?

Answer 23

The sterno-clavicular joint, the acromioclavicular joint, the gleno-humeral (shoulder) joint and the scapula-thoracic joint (referred to often as a virtual or physiological joint).

Question 24

Describe the gleno-humeral joint.

Answer 24

The gleno-humeral joint is a ball-and-socket joint. The glenoid fossa is shallow, but slightly deepened by a cartilaginous labrum. The rotator cuff group is required for stability. It holds the humeral head within the glenoid fossa. The rotator cuff group depresses the humeral head.

Question 25

Describe the main arterial supply of the shoulder and arm region.

Answer 25

The subclavian artery passes over the first rib to become the axillary artery. At the lower border of the teres major it becomes the brachial artery. The brachial artery gives off a larger branch: profunda brachii. At the level of the elbow, the brachial artery divides into ulnar and radial arteries.

Question 26

Describe the main venous drainage of the shoulder and arm region.

Answer 26

The cephalic vein runs up the lateral border of the arm: the basilic runs up the medial border. The basilic veins join venae comitantes to from the axillary vein. The cephalic vein joins the axillary vein in the axilla. Becomes the subclavian vein at the level of the first rib.

Question 27

Describe the principal lymph drainage of the shoulder and arm region.

Answer 27

Lymph vessels, like veins, arranged in a superficial and deep system. Run along veins. Main groups of nodes: cubital lymph nodes, delto-pectoral lymph nodes, axillary lymph nodes and subclavian lymph nodes.

Question 28

How can breast cancer treatment lead to lymphoedema of the arm, forearm and hand?

Answer 28

Since the axillary lymph nodes are very important in draining the breast, removing axillary lymph nodes in breast cancer can lead to lymphoedema.

Question 29

Describe how the brachial nerve plexus is divided into 'zones'.

Answer 29

``` Roots - formed by anterior rami. Trunks Divisions Cords Terminal branches (peripheral nerves). ```

Question 30

Give some features of the clavicles which would help you orientate it into its anatomical position.

Answer 30

Its superior surface is smooth; it's inferior surface is rough. It is flattened laterally (acromial end) and is s-shaped, with its lateral 1/3 being concave anteriorly, and medial 2/3 convex anteriorly.

Question 31

Briefly, how do you test the trapezius muscle's function - and what is its innervation?

Answer 31

Ask the patient to raise both shoulders against resistance. | Nerve supply is accessory nerve and C3,4.

Question 32

Which muscle is palpable in the anterior axillary fold and how do you test it and its innervation?

Answer 32

Pectoralis major. Ask the patient to adduct the abducted arm against resistance. Nerves = lateral and medial pectoral.

Question 33

Which muscles are palpable in the posterior axillary fold and how do you test it and its innervation?

Answer 33

Teres major and latissimus dorsi. The teres major is tested by asking the patient to adduct the arm against resistance. Nerve = lower subscapular. Latissimus dorsi is tested by adducting the arm against resistance. (Or abduct and flex 45 degrees each way and then adduct). Nerve = thoracodorsal.

Question 34

How do you test the serratus anterior muscle and what is its innervation?

Answer 34

Ask the patient to outstretch both arms with their palms flat against a wall. Press forward strongly. Nerve = long thoracic.

Question 35

How do you test the deltoid muscle? What is its innervation?

Answer 35

Ask the patient to abduct the arm against resistance. | Nerve = axillary.

Question 36

Name the carpal bones which comprise the proximal and distal rows.

Answer 36

Scaphoid, lunate, triquetrum and pisiform = proximal row. | Trapezium, trapezoid, capitate and hamate = distal row.

Question 37

Describe the elbow joint.

Answer 37

A complex joint involving three separate articulations which share a common synovial cavity. The joints between the trochlear notch of the ulna and the trochlea of the humerus and between the head of the radius and the capitulum of the humerus are primarily involved with hinge-like flexion and extension of the forearm. The joint between the head of the radius and the radial notch of the ulna is involved with pronation and supination of the forearm. Typically considered a separate joint, the PROXIMAL RADIO-ULNAR joint.

Question 38

What are the borders and contents of the cubital fossa?

Answer 38

A triangular depression between two forearm muscles: the brachioradialis muscle and pronator teres muscle. The base is an imaginary horizontal line between the medial and lateral epicondyles. The bed is formed by the brachialis muscle. Major contents are the tendon of the biceps brachii, the brachial artery and the median nerve. Bifurcation of the brachial artery normally occurs in the apex of the fossa.

Question 39

Which structure separates the median cubital vein from the brachial artery and median nerve below in the cubital fossa?

Answer 39

The bicipital aponeurosis.

Question 40

Describe how the hand is supinated and pronated.

Answer 40

At the elbow, the superior articular surface of the radial head spins on the capitulum, while the articular surface on the side of the head slides against the radial notch of the ulna. At the distal radio-ulnar joint, the ulnar notch of the radius slides anteriorly over the convex surface of the head of the ulna. The muscles involved in this pronation are the pronator teres and the pronator quadratus. The muscles which return the hand to a supine position are the supinator and the biceps brachii. The bones are held together by the anular ligament of the radius at the proximal radio-ulnar joint, the interosseous membrane and the articular disc at the distal radio-ulnar joint.

Question 41

What compartments are present in the forearm?

Answer 41

Anterior compartments of the forearm: superficial and deep. | Posterior compartment of the forearm.

Question 42

Which muscles comprise the superficial anterior compartment of the forearm?

Answer 42

Pronator teres, flexor carpi radialis (FCR), palmaris longus (PL), flexor digitorum superficialis (FDS), flexor carpi ulnaris (FCU).

Question 43

Which muscles comprise the deep anterior compartment of the forearm?

Answer 43

Flexor digitorum profundus (FDP), flexor pollicis longus (FPL), pronator quadratus (PQ).

Question 44

Which muscles comprise the posterior compartment of the forearm?

Answer 44

Muscles that move the wrist joint: extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor carpi ulnaris (ECU). Muscles which move the digits: extensor digitorum (ED), extensor indicis (EI), extensor digiti minimi (EDM). Muscles that move the thumb: abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL). Supinator and brachioradialis (misc)

Question 45

What divides the forearm into anterior and posterior muscular compartments and what are the typical functions of muscles found in each of them?

Answer 45

Divided by interosseous membrane. Anterior compartment muscles typically are flexors and pronators. Posterior compartment muscles are typically extensors and supinators.

Question 46

Describe the skeleton of the hand.

Answer 46

8 carpal bones - arranged in a proximal and distal row. 5 metacarpals. 5 proximal phalanges. 4 middle phalanges (the 1st digit (thumb) doesn't have one). 5 distal phalanges.

Question 47

Which bones and ligaments are involved with the radiocarpal wrist joint?

Answer 47

Distal radius and the proximal row of carpal bones (scaphoid, lunate and triquetrum). Ligaments = palmar radiocarpal ligament, palmar ulnocarpal ligament, dorsal radiocarpal ligament and intercarpal ligaments. Reinforced by radial and ulnar collateral ligaments.

Question 48

Describe the midcarpal, or intercarpal, joints.

Answer 48

Plane synovial joints which permit sliding and gliding movements.

Question 49

Which muscle of the anterior forearm muscular compartment is vestigial and how would you check if it is present in a patient?

Answer 49

The palmaris longus is vestigial. Check it is present by asking the patient to oppose their thumb and little finger. N.B. the median nerve lies just lateral to this tendon before entering the carpal tunnel.

Question 50

Describe the flexor digitorum profundus.

Answer 50

Proximal attachment is the proximal 3/4 of the ulna. Distal attachment is the bases of the distal phalanges of digits 2-5. Primary role is to flex the distal interphalangeal joints. Also flexes the metacarpophalangeal joints and the wrist because its tendons cross these joints. Medial 1/2 supplied by ulnar nerve, lateral half by median nerve.

Question 51

Describe the flexor digitorum superficialis muscle.

Answer 51

Proximal attachment is the medial epicondyle, ulnar collateral ligament and coronoid process of ulna and superior half of anterior aspect of radius. Distal attachments are the bodies of the middle phalanges of the medial 4 digits (2-5). Flexes proximal interphalangeal joints, but also the elbow, wrist and metacarpophalangeal since it crosses these.

Question 52

Describe the flexor pollicis longus muscle.

Answer 52

Arises from anterior aspect of radius and inserts into base of distal phalanx of the thumb. Flexes distal phalanx of thumb, but can also flex proximal phalanx as it crosses the joint.

Question 53

Compare the supinator ability of the biceps brachii and the supinator muscles.

Answer 53

The most powerful supinator of the forearm is the biceps brachii, which acts primarily when the forearm is flexed. The supinator can supinate a forearm whether it is flexed or extended.

Question 54

Describe the supinator muscle.

Answer 54

Arises from lateral epicondyle of humerus, the radial collateral ligament of the elbow joint and the anular ligament of the proximal radioulnar joint. Inserts into lateral, posterior and anterior surfaces of the radius. Supinates the forearm and hand, whether flexed or extended.

Question 55

Describe the brachioradialis muscle.

Answer 55

Proximal attachment = proximal 2/3 of lateral supracondylar ridge of distal humerus. Distal attachment = lateral distal radius just proximal to styloid process. Accessory FLEXOR of forearm.

Question 56

Describe the attachments of the pronator teres (superficial compartment) and pronator quadratus (deep compartment).

Answer 56

Pronator teres attaches proximally to the median epicondyle via the common flexor tendon and to the coronoid process of ulna. It attaches distally to a midshaft roughening on the radius. Rotates the radius on the ulna and helps flex the forearm at the elbow. The pronator quadratus arises from the medial aspect of the anterior surface of the distal 1/4 of the ulna and inserts into the distal 1/4 of the lateral border and anterior surface of the shaft of the radius. Pronates the hand. Assisted by pronator teres when additional power required.

Question 57

Describe the palmaris longus.

Answer 57

Arises from the medial epicondyle of the humerus by the common flexor tendon, inserts into palmar aponeurosis. Flexes the hand at the wrist.

Question 58

Describe the flexor carpi radialis muscle.

Answer 58

Arises from common flexor tendon at medial epicondyle of humerus. Attaches to base of 2nd and 3rd metacarpal bones. Flexes the hand at the wrist joints and aids in wrist abduction.

Question 59

Describe the flexor carpi ulnaris muscle.

Answer 59

Arises from medial epicondyle of humerus by common flexor tendon and its ulnar head arises from medial margin of olecranon and posterior border of the ulna. Inserts into pisiform bone; an extension attaches to the hook of hamate and the base of the 5th metacarpal. Flexes and adducts the hand at the wrist.

Question 60

Describe the extensor carpi radialis longus muscle.

Answer 60

Proximal attachment is the lateral supracondylar ridge of the humerus. Distal attachment is the base of the 2nd metacarpal. Extends and abducts hand at the wrist joint.

Question 61

Describe the extensor carpi radialis brevis muscle.

Answer 61

Arises from lateral epicondyle of the humerus. Inserts into base of the 3rd metacarpal bone. Extends and abducts hand at the wrist.

Question 62

Describe the extensor carpi ulnaris muscle.

Answer 62

Arises from the lateral epicondyle of the humerus and the posterior border of the ulna. Attaches to medial side of 5th metacarpal. Extends and adducts hand at wrist joint.

Question 63

Describe the extensor digitorum muscle.

Answer 63

Extends from lateral epicondyle of the humerus to insert as extensor expansions into the medial 4 digits. Performs extension of the metacarpophalangeal and interphalangeal joints. Also participates in wrist extension with the fingers extended.

Question 64

Describe the extensor digiti minimi muscle.

Answer 64

Arises from the lateral epicondyle of the humerus and inserts as an extensor expansion of the 5th digit. Extends 5th digit: acts with many other finger and wrist extensors and is usually not tested clinically as an individual muscle.

Question 65

Describe the extensor indicis muscle.

Answer 65

Arises from posterior surface of ulna and interosseous membrane. Attaches as an extensor expansion of the 2nd digit. Extends all joints of the index finer - can help other extensors of the wrist.

Question 66

Describe the extensor pollicis longus muscle.

Answer 66

Arises from posterior surface of middle 1/3 of the ulna and interosseous membrane. Attaches to the base of the distal phalanx of the thumb. Extends the distal phalanx of the thumb at the metacarpophalangeal and interphalangeal joints.

Question 67

Describe the extensor policis brevis muscle.

Answer 67

Arises from posterior surface of radius and interosseous membrane and attaches to the base of the proximal phalanx of the thumb. Extends the proximal phalanx of the thumb at the metacarpophalangeal joint.

Question 68

Describe the abductor pollicis longus muscle.

Answer 68

Posterior aspect of ulna, radius and interosseous membrane. Attaches to base of 1st metacarpal bone. Abducts, extends and laterally rotates thumb at the carpometacarpal joint.

Question 69

What is the anatomical snuffbox?

Answer 69

The area proximal to the pollux between the extensor pollicis brevis and extensor pollicis longus, which is important in determining if the scaphoid is fractured.

Question 70

Describe the carpal tunnel.

Answer 70

Bony attachments: laterally = tubercles of scaphoid and trapezium bones. Medially = hook of hamate and pisiform bone. Roof is flexor retinaculum (preventing bowing of tendons). Contains median nerve, flexor pollicus longus tendon, 4 tendons of FDP and 4 tendons of FDS.

Question 71

Describe briefly the palmar aponeurosis.

Answer 71

Overlies the long flexor tendons of the hand - is proximally continuous with the flexor retinaculum and distally continuous with the fibrous digital sheaths.

Question 72

Which muscles comprise the thenar and hypothenar muscle compartments?

Answer 72

Thenar muscles: abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. Hypothenar muscles: abductor digiti minimi, flexor digiti minimi and opponens digiti minimi.

Question 73

Describe the adductor pollicis muscle.

Answer 73

Wide attachment to middle metacarpal. Fan-shaped - attaches to proximal phalanx of the thumb.

Question 74

Describe the lumbrical muscles.

Answer 74

Proximal attachments = flexor digitorum profundus tendons - attach to the extensor expansion. Flex the MCPs, extend the IPs.

Question 75

Describe the dorsal and palmar interossei muscles.

Answer 75

Palmar interossei muscles adduct the digits ("PAD") - attach proximally to the bases of the metacarpal bones between them - insert away from the axial line. 3 muscles. Dorsal interossei muscles attach distally towards the axial line towards the axial line to abduct the digits - 4 muscles. "DAB".

Question 76

Describe the passage of the FDP and FDS tendons through the carpal tunnel.

Answer 76

They pass beneath the flexor retinaculum and enter a common synovial sheath. They then split and enter digital synovial sheaths: the thumb and little fingers have continuous sheaths. The FDS splits around the FDP and inserts into the middle phalanx: the FDP tendons insert into the distal phalanx.

Question 77

Which type of movement occurs at intercarpal joints?

Answer 77

Gliding.

Question 78

What movements are permitted by the carpometacarpal and intermetacarpal joints?

Answer 78

Flexion and extension, radial and ulnar deviation (abduction and adduction) and circumduction.

Question 79

What movements are permitted by metacarpophalangeal (knuckles) and interphalangeal joints?

Answer 79

``` MCPs = flexion and extension, abduction and adduction. IPs = flexion and extension only. Strong collateral ligaments prevent abduction and adduction. ```

Question 80

Which muscles are involved in a power grip?

Answer 80

Long flexors of fingers and thumb and intrinsic muscles of the hand. EXTENSORS of the wrist joint.

Question 81

Which muscles are involved in a precision grip?

Answer 81

Wrist and fingers held rigidly by long flexors and extensors. The intrinsic muscles of the hand carry out necessary fine movements. Notably, the adductor pollicis and 1st dorsal interosseus.

Question 82

Which muscles are involved in a hook grip?

Answer 82

Long flexors of digits mainly. Consumes little energy, e.g. carrying a shopping bag.

Question 83

Why can the hand be adducted to a greater degree than it can be abducted at the wrist joint?

Answer 83

Since the styloid process of the radius extends further distally than the ulnar styloid process.

Question 84

What is innervated by the musculocutaneous nerve? Which cord does it originate from?

Answer 84

Originates from lateral cord to innervate all muscles in anterior compartment of arm, and sensory to anterolateral forearm (as the lateral cutaneous/ antebrachial nerve).

Question 85

What is innervated by the median nerve? Which cord does it originate from?

Answer 85

Originates from medial and lateral cords. Motor to all muscles in anterior compartment of the forearm (except the flexor carpi ulnaris and medial half of flexor digitorum profundus), three thenar muscles and two lateral lumbrical muscles. Sensory to skin over the palmar surface of the lateral three and one-half digits and over the lateral side of the palm and middle of the wrist.

Question 86

What is innervated by the ulnar nerve? Which cord does it originate from?

Answer 86

Originates from medial cord. Motor to intrinsic muscles of the hand (except three thenar muscles and two lateral lumbricals), also flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the forearm. Sensory over the palmar surface of the medial one and one-half digits and associated palm and wrist and skin over the dorsal surface of the medial one and one-half digits.

Question 87

What is innervated by the radial nerve? Which cord does it originate from?

Answer 87

Originates from the posterior cord. Motor to the muscles in the posterior compartments of the arm and forearm. Sensory to skin on the posterior aspects of the arm and forearm, the lower lateral surface of the arm and the dorsal lateral surface of the hand.

Question 88

What is innervated by the axillary nerve? Which cord does it originate from?

Answer 88

Originates from the posterior cord. Motor to deltoid and teres minor (a rotator cuff muscle). Sensory to skin over upper lateral part of the arm ("regiment badge")

Question 89

What is the function of the brachial plexus?

Answer 89

To rearrange the nerve fibres from C5-T1 into bundles travelling to appropriate parts of the limb. All nerves supplying extensor muscles pass through a bundle in the plexus named the posterior cord. All nerves supplying flexor muscles pass through bundles in the plexus named the lateral and medial cords. The cords are named according to their relationship to the axillary artery.

Question 90

How is the axillary nerve commonly damaged? How do you test this?

Answer 90

Commonly damaged by shoulder dislocations and fractures of surgical neck of the humerus. Don't ask the patient to abduct their arm; the axillary nerve gives off a superior lateral cutaneous nerve of the arm, hence damage would result in an area of anaesthesia at the "regimental badge" area.

Question 91

How is the radial nerve commonly damaged and which signs indicate this?

Answer 91

Commonly damaged by mid-humeral fractures. Causes wrist-drop and results in great weakness of the "power grip".

Question 92

Where is the ulnar nerve most vulnerable to compression, cuts and fractures and what is the result of damage to it?

Answer 92

Vulnerable where is passes posterior to the medial epicondyle. Results in claw-like hand due to loss of lumbrical contraction (loss of flexion of MPJs and weakened extension of IPJs) Thumb, middle and index fingers largely spared. Commonly damaged at wrist in self-harm. Also involved in cubital tunnel syndrome - where the nerve can become compressed between the 2 heads of the flexor carpi ulnaris.

Question 93

Explain the ulnar paradox: "the closer to the paw, the worse the claw"

Answer 93

Ulnar injury at wrist is more severe than at the elbow since the ulnar nerve also innervates the ulnar half of the FDP, so flexion of the IPJs is weakened and therefore there is less claw-like appearance.

Question 94

What causes wasting of the thenar eminence?

Answer 94

Carpal tunnel syndrome. | Compression of median nerve.

Question 95

What is Erb-Duchenne Palsy?

Answer 95

Injuries to upper roots of the brachial plexus. Arise from stretching the neck relative to the shoulder, such as falls onto the shoulder and in childbirth. Results in "waiter's tip" - unopposed pronation.

Question 96

What is Klumpke's palsy?

Answer 96

Injuries to the lower roots of the brachial plexus. Arise from over-abduction, such as gripping overhead to break a fall. Since T1 supplies small muscles of hand (ulnar), you get a clawed hand.

Question 97

In Carpal Tunnel syndrome, why is sensation to the palmar surface of the hand preserved?

Answer 97

Palmar sensation is supplied by the palmar cutaneous nerve (a branch of the median nerve) which passes superficially to the flexor retinaculum and hence doesn't pass through the carpal tunnel.