Session 3 - The Hand

Question 1

What is the carpus comprised of?

Answer 1

the carpus is comprised of eight small bones that articulate with each other at small joints. The bones are roughly arranged into two rows of four bones: one proximal, one distal. The distal radius articulates with the scaphoid and lunate to form the radiocarpal joint.

Question 2

What is the hand composed of?

Answer 2

The hand is composed of many small bones and joints.
• The metacarpals are located distal to the carpus. They are numbered 1 – 5 from the lateral (thumb) side to the medial (little finger) side.
• The bones of the digits are phalanges (singular: phalanx). There are three phalanges in each finger (digits 2-5) and two phalanges in the thumb (digit 1).
• The three phalanges of the fingers are named proximal, middle, and distal phalanges.
• The two phalanges of the thumb are named proximal and distal phalanges.

Question 3

What is the terminology of the hand?

Answer 3

Terminology – the digits may be referred to by their number from lateral to medial (1-5) or by their names (thumb, index finger, middle finger, ring finger, little finger). In clinical practice it is preferred to identify them by their name, not their number, as it is less confusing

Question 4

Where are the small joints located?

Answer 4

Small joints are located between the carpal bones, metacarpals, and phalanges. They are all reinforced by ligaments.

Question 5

What are the Carpometacarpal joints located?

Answer 5

• Carpometacarpal joints (CMCJs) are located between the distal row of carpal bones and the proximal parts (the bases) of the metacarpals.
o The first carpometacarpal (CMC) joint is between the trapezium and the 1st (thumb) metacarpal. It is a saddle joint and is key to the range of movement possible at the thumb.

Question 6

Where are the metacarpophalangeal joints located?

Answer 6

Metacarpophalangeal joints (MCPJs) are often known as the ‘knuckles’, these joints are located between the distal parts (the heads) of the metacarpals and the proximal phalanges. The metacarpophalangeal joints are condyloid synovial joints.

Question 7

Where are the interphalangeal joints located?

Answer 7

Interphalangeal joints (IPJs) are between the phalanges. They are hinge synovial joints.

Question 8

What phalanges does the thumb and fingers contain?

Answer 8

The thumb contains two phalanges so there is only one interphalangeal joint (IPJ) in the thumb.
• The fingers contain three phalanges so there are two interphalangeal joints:
• the proximal interphalangeal (PIP) joints are located between the proximal and middle phalanges.
• the distal interphalangeal (DIP) joints are between the middle and distal phalanges.

Question 9

What is the importance of grips?

Answer 9

The human hand is highly evolved and allows us to manipulate objects in a variety of ways. The hand and digits can perform a wide range of grips. For example, we use a power grip to hold or squeeze objects tightly. The hook grip is important for carrying objects with handles, such as bags. The precision grip allows us to hold objects between the pads of our thumb and fingers, such as a pen or needle. Impaired function of the hand and digits can have a significant effect on patients and how they are able to carry out their daily activities.

Question 10

What are the movements of the fingers?

Answer 10

The fingers (digits 2-5) are able to move in the following ways:
• Flexion and extension
• Abduction (moving the fingers apart) and adduction (bringing the fingers together).

Question 11

What are the movements of the thumb?

Answer 11

Movements of the thumb
The movements of the thumb are a little more complex. They are:
• Flexion and extension
• Abduction and adduction
• Opposition (a mixture of flexion, adduction, and internal rotation of the thumb metacarpal).

Question 12

What are the muscles of the hand?

Answer 12

Extrinsic Muscles of the Hand
Movements of the fingers and thumb are controlled by both extrinsic and intrinsic muscles.
The extrinsic muscles are located in the anterior and posterior forearm and their tendons travel into the hand.

Question 13

What are the muscles of the anterior forearm?

Answer 13

Muscles of the Anterior Forearm
The muscles of the anterior forearm that are the primary flexors of the wrist are:
• Flexor carpi radialis - inserts onto the 2nd (index) metacarpal.
• Flexor carpi ulnaris - inserts onto the 5th (little finger) metacarpal.
• Palmaris longus (if present) - inserts onto the palmar fascia.

Question 14

What do anterior compartment muscles do?

Answer 14

Anterior compartment muscles also flex the digits. They travel through the carpal tunnel and into the hand:
• Flexor digitorum superficialis (FDS).
• Flexor digitorum profundus (FDP).
• Flexor pollicis longus (FPL).
Because their tendons cross the wrist, these muscles also contribute to wrist flexion.

Question 15

What are the tendons of the anterior compartment muscles located?

Answer 15

The tendon of flexor digitorum superficialis (FDS) splits into two ‘slips’ which insert on either side of the middle phalanx of digits 2-5. It flexes the MCP joints and PIP joints of digits 2-5.
• The tendon of flexor digitorum profundus (FDP) passes through the gap in the FDS tendon to insert onto the palmar aspect of the distal phalanx of digits 2-5. It is the only muscle capable of flexing the DIP joint. It also flexes the PIP joint and the MCP joint of digits 2-5.
• The tendon of flexor pollicis longus (FPL) inserts onto the distal phalanx of the thumb. It flexes the IP joint of the thumb and is the only muscle that can do so.

Question 16

What is the CR of tendons?

Answer 16

It is important for clinical practice to know these specific distal insertion points of the long flexor tendons. When patients present with injuries to the hand, such as lacerations, you must be able to test the movements of the digits to assess if the tendons have been injured – being able to do this competently relies on knowing where the tendons insert and what movements they control.

Question 17

What are flexor tendon sheaths ?

Answer 17

Fibrous sheaths enclose the long flexor tendons. They maintain the position of the flexor tendons in the midline of each finger. Within the fibrous sheaths, the tendons are enclosed within a synovial sheath, which reduces friction and allows the tendons to slide freely within their fibrous sheath during flexion and extension. The thick palmar aponeurosis protects the long flexor tendons, tendon sheaths and vessels as they pass through the palm of the hand.

Question 18

What is tenosynovitis?

Answer 18

If penetrating injuries of the hand and fingers (e.g. lacerations, bites or thorns piercing the skin) pierce the tendon sheaths they may become infected. Inflammation of the tendon and synovial sheath is called tenosynovitis.

Question 19

What are the intrinsic muscles of the hand?

Answer 19

Also referred to as the small muscles of the hand, both the origins and insertions of the intrinsic muscles are within the hand itself. There are four groups of intrinsic muscles and one single muscle that does not fit into any of the groups. The four groups are the:
• thenar eminence – contains three muscles and located proximal to the thumb.
• hypothenar eminence – contains three muscles and located proximal to the little finger.
• lumbricals – four muscles, located between the metacarpals.
• interossei – seven muscles, also located between the metacarpals.

Question 20

What is another muscle of the hand?

Answer 20

The remaining muscle is a muscle of the thumb called adductor pollicis.
The intrinsic muscles of the hand are innervated by the ulnar and median nerves.

Question 21

What is the thenar eminence?

Answer 21

Thenar Eminence
This is the fleshy mass on the palm of the hand at the base of the thumb. It contains:
• Flexor pollicis brevis (FPB) - flexes the thumb.
• Abductor pollicis brevis (APB) - abducts the thumb.
• Opponens pollicis - (OP) - opposes the thumb.

Question 22

Where is the Opponens Pollicis located?

Answer 22

The opponens pollicis is deep to the flexor and abductor. The thenar muscles are attached to the carpal bones proximally.

Question 23

What is the movement, insertion and innervation of the thenar eminence?

Answer 23

FPB - flexion, proximal phalanx
APB - Abduction, proximal phalanx, lateral aspect
OP - opposition, 1st metacarpal

All innervated by: recurrent branch of median nerve

Question 24

Why is the thenar eminence affected in CTS?

Answer 24

The recurrent branch of the median nerve leaves the median nerve after it has passed through the carpal tunnel, therefore the thenar eminence muscles will be affected in carpal tunnel syndrome. If left untreated, they become weak and atrophy.

Question 25

What does the adductor pollicis do?

Answer 25

This muscle moves the thumb but differs from the thenar eminence muscles in two ways: it is located deep in the palm, not in the thenar eminence, and it is innervated by the ulnar nerve.
Adductor pollicis is attached to the 3rd (middle) metacarpal and to the proximal phalanx of the thumb. Contraction of the muscle pulls the thumb towards the palm.

Question 26

What is the importance of thenar muscles?

Answer 26

The thenar muscles are important for a precision grip. The thumb is abducted, flexed, and internally rotated at the CMC joint so it can oppose with the one of the fingers. This grip can be performed with or without power.

Question 27

What is the hypothenar eminence?

Answer 27

This is the fleshy mass on the medial side of the palm of the hand, proximal to the little finger. It contains three small muscles that act upon the little finger. They mirror the thenar eminence muscles, in their names and locations.
• Flexor digiti minimi (FDM) - flexes the little finger.
• Abductor digiti minimi (ADM) - abducts the little finger.
• Opponens digiti minimi (ODM) - opposes the little finger

Question 28

What is the movement, insertion and innervation for the hypothenar muscles?

Answer 28

FDM - flexion - proximal phalanx
ADM - abduction - proximal phalanx
ODM - opposition - 5th metacarpal

All innervated by the deep branch of the ulnar nerve

Question 29

What are the lumbricals?

Answer 29

There are four lumbrical muscles, one for each finger (digits 2-5). Their origins are the tendons of flexor digitorum profundus. They then travel along the lateral aspects of digits 2-5 to insert onto the dorsal aspects of digits 2-5. The action of the lumbricals is to flex the MCP joints and simultaneously extend the IP joints.

Question 30

What are the innervation of the lumbricals?

Answer 30

The innervation of the lumbricals follows that of the FDP tendons from which they arise:
• the lateral two (digits 2 and 3) are innervated by the median nerve.
• the medial two (digits 4 and 5) are innervated by the ulnar nerve.

Question 31

What are the interossei?

Answer 31

These muscles are attached to, and located between, the metacarpals and insert onto the dorsal aspects of digits 2-5. There are two groups, a palmar group, and a dorsal group.

Question 32

What are the arrangements for the interosseous muscles?

Answer 32

There are three palmar interosseous muscles and four dorsal interosseous muscles.
● The arrangement of the palmar interossei and their insertion points allows them to adduct the fingers (i.e. draw them towards the middle finger) when they contract.
● The arrangement of the dorsal interossei and their insertion points allows them to abduct the fingers (i.e. move away from the middle finger) when they contract.

Question 33

How can the movements of the interrossei muscles be remembered?

Answer 33

Their movements can be remembered by ‘PAD-DAB’ (Palmar ADduct, Dorsal ABduct).

Question 34

What is the dorsi m of the hand like?

Answer 34

The dorsum of the hand is far less complex than the palm in terms of muscles – only the four dorsal interossei are seen on the dorsal aspect. The extensor tendons are often visible under the skin over the dorsum of the hand.

Question 35

What is the venous drainage of the dorsum of the hand like?

Answer 35

The superficial veins of the dorsum of the hand are often visible and palpable under the skin. They comprise the dorsal venous network, but the pattern is variable between individuals. Veins of the dorsal venous network can be cannulated. The dorsal venous network drains into the cephalic vein laterally and into the basilic vein medially.

Question 36

What is the extensor expansion?

Answer 36

Also called the extensor hood, this fibrous structure is located on the dorsal aspect of the digits. It is attached to the base of the proximal phalanx and gives rise to a central slip and two marginal slips. The central slip inserts on the middle phalanx and the marginal slips converge on the distal phalanx.

Question 37

What inserts onto the extensor expansion?

Answer 37

The tendons of ED, EI and EDM insert onto the dorsal aspect of the extensor expansion. This helps keep the tendons fixed in the midline of the digits. The lumbricals and interossei insert onto the sides of the proximal parts of the extensor expansion. Via this attachment, they contribute to extension of the interphalangeal joints of the fingers.

Question 38

What is the anatomical snuffbox? (ASB)

Answer 38

The anatomical snuffbox (ASB) is a triangular-shaped depression on the lateral aspect of the wrist, at the base of the thumb. It is best seen when the thumb is fully extended.

Question 39

What are the boundaries of the ASB?

Answer 39

The boundaries of the snuffbox are the tendon of EPL medially and the tendons of EPB and APL laterally.

Question 40

What is the CR of the ASB?

Answer 40

It is a clinically important region because:
• The scaphoid bone is located in the floor of the ASB. ASB tenderness on palpation may indicate a scaphoid fracture.
• The radial artery travels through it.
• The cephalic vein travels across it.
• The superficial branch of the radial nerve travels over the anatomical snuffbox to supply the skin over the lateral aspect of the dorsum of the hand.

Question 41

What arteries supply the hand?

Answer 41

The radial and ulnar arteries supply the hand. These are the terminal branches of the brachial artery.
• The radial artery courses down the lateral aspect of the forearm. The radial pulse can be palpated over the lateral aspect of the wrist.
• The ulnar artery courses down the medial aspect of the forearm. The ulnar nerve travels alongside the ulnar artery.

Question 42

What do the arteries of the hand form?

Answer 42

The radial and ulnar arteries anastomose deep in the palm to form two palmar arches:
• the superficial palmar arch is formed largely by the ulnar artery with a smaller contribution from the radial artery.
• the deep palmar arch is formed largely by the radial artery with a smaller contribution from the ulnar artery.
The palmar arches give rise to metacarpal and digital arteries that supply the palm and digits. These are accompanied by digital nerves.

Question 43

How can sensation in the hand can be assessed?

Answer 43

by examining the territories of the peripheral nerves or the dermatomes.

Question 44

What territories do peripheral nerves innervate the skin?

Answer 44

Several peripheral nerves innervate the skin of the upper limb, we are only going to concentrate on the territories of the median, ulnar and radial nerves in the hand. The territories of these nerves are as follows:
• Median: the palmar surface of the lateral side of the hand, the palmar surface of the lateral 3 ½ digits, the skin over the dorsum of the distal phalanges of the lateral 3 ½ digits.
• Ulnar: the palmar and dorsal surfaces of the medial side of the hand and the medial 1 ½ digits.
• Radial: the dorsal surface of the lateral side of the hand and the skin over the dorsum of the lateral 3 ½ digits as far as the DIP joint.

Question 45

Why is sensation tested over specific areas?

Answer 45

These are the approximate territories of each nerve, but there is variation between individuals. For this reason, sensation is tested over specific areas, where we can be fairly sure that the skin is innervated by the peripheral nerve we want to assess.

Question 46

What space is each peripheral nerve tested for?

Answer 46

• Median: tested on the central palm, just proximal to the middle finger.
• Ulnar: tested on the medial border of the hand
• Radial: tested on dorsum of the hand in the thumb and index webspace.

Question 47

What is a dermatome?

Answer 47

A dermatome is a region of skin innervated by a single spinal nerve.

Question 48

What is the upper limb innervated by?

Answer 48

The upper limb is innervated by the brachial plexus and spinal nerves C5 – T1.

Question 49

What is each region innervated by?

Answer 49

The regions innervated by these nerves are:
● C4: the superior aspect of the shoulder.
● C5: the lateral shoulder over the deltoid, and anterior and posterior aspects of the arm.
● C6: the lateral side of the anterior and posterior surfaces of the forearm, the lateral sides of the anterior and posterior surfaces of the palm, and the anterior and posterior surfaces of the thumb and index finger.
● C7: the anterior and posterior surfaces of the middle finger and middle of the palm (over the 3rd metacarpal).
● C8: the medial side of the anterior and posterior surfaces of the forearm, the medial side of the anterior and posterior surfaces of the palm, and the anterior and posterior surfaces of the ring and little fingers.
● T1: the medial side of the anterior and posterior surfaces of the arm.

Question 50

What does testing dermatomes give us info on?

Answer 50

Testing sensation in dermatomes C5 – T1 gives us information about the spinal nerves and their corresponding spinal cord segments. The areas of skin innervated by the spinal nerves (dermatomes) are different to the areas supplied by peripheral nerves because of how the spinal nerve fibres are ‘shuffled’ in the brachial plexus and distributed within the peripheral nerves.

Question 51

What areas do you test each dermatome for?

Answer 51

To test the dermatomes, sensation is tested over the following areas:
● C5: upper lateral arm, over the deltoid muscle.
● C6: thumb.
● C7: middle finger.
● C8: little finger.
● T1: medial border of the arm, just proximal to the elbow.

Question 52

What is the CR for testing the tendons of FDP and FPL?

Answer 52

In the case of palmar injuries (e.g., a laceration over the palmar aspect of a finger), we need to assess if the long flexor tendons are intact. The tendons of FDS and FDP both cross, and hence can move, the PIP joint. However, only FDP can move the DIP joint. To test FDP, the PIP joint is held immobile by the examiner and the patient is asked to flex the finger. If the FDP tendon is intact, flexion is seen at the DIP joint. To test the tendon of FPL, movement at the IP joint of the thumb is assessed.

Question 53

What is dupuytren’s contracture?

Answer 53

In this condition, the fingers (usually the little and ring fingers) are pulled into flexion by progressive fibrosis of the palmar fascia and palmar aponeurosis. The palmar fascia is attached to the flexor tendon sheaths of the fingers. The fascia shortens and pulls the fingers into flexion. The fascia can be released surgically.

Question 54

What is arthritis?

Answer 54

Osteoarthritis is ‘wear and tear’ arthritis and is more common in older people. It primarily affects large, ‘load bearing’ joints like the hips and knees. However, rheumatoid arthritis is an autoimmune condition that affects various synovial joints, and the small joints of the hands are typically involved. The MCP and PIP joints are predominantly affected. Rheumatoid arthritis can damage these joints causing significant deformity such as ulnar deviation of the digits at the MCP joints, and fixed flexion and extension deformities of either of the interphalangeal joints. This can lead to significant functional impairment for these patients.

Question 55

What is the boxers fracture?

Answer 55

Fracture of the 5th metacarpal
Otherwise known as a ‘boxer’s fracture’, as it is typically sustained by punching something hard, there is usually pain, swelling and tenderness over the 5th metacarpal.