The Hand Flashcards
What does prehensile mean?
Capable of grasping
What type of joints are the small joints of the hand? What disesase does this mean they are therefore vulnerable to?
Synovial joints
Vulnerable to rheumatoid arthritis - when the immune system attacks lining of the joints (called the synovium)
What joint is circled?
Carpometacarpal joint
Surface anatomy of the hand
What joints are the ‘knuckles’?
The metacarpophalangeal joints
What 2 groups of muscles bring about movements of the fingers and thumb?
- Extrinsic muscles
- Intrinsic muscles
Where are the extrinsic muscles of the hand found?
Located in the anterior and posterior compartments of the forearm whose tendons travel down into the hand
Where are the tendons of the extrinsic muscles of the hand most vulnerable?
Most vulnerable to injury at the wrist or in the hand
Where are the intrinsic muscles of the hand located?
Both their origins and insertions are located within the hand itself. These are, by definition, short, or small muscles. Many of them have the term ‘brevis’ in their name.
Broadly, what type of movements are the extrinsic / intrinsic muscles of the hand responsible for?
Extrinsic - They control crude movements and produce a forceful grip.
Intrinsic - They are responsible for the fine motor functions of the hand.
Where do almost all of the intrinsic muscles of the hand lie?
Almost all of them lie in the palm of the hand (the dorsum of the hand has just one set)
Describe the organisation of the intrinsic muscles of the hand
- 4 groups of muscles
- 1 single muscle
What are the 4 groups of intrinsic muscles?
- Thenar muscles
- Hypothenar muscles
- Lumbricals
- Interosseous muscles (interossei)
What is the single intrinsic muscle?
Adductor pollicis
How many muscles make up the ‘thenar’ muscle group? Where do they lie? What is their function?
- 3 muscles that lie in the palm of the hand at the base of the thumb
- Produce the bulge - ‘thenar eminence’
- Responsible for fine movements of the thumb
What innervates the thenar muscles?
The recurrent branch of the median nerve
How many muscles make up the ‘hypothenar’ muscle group? Where do they lie? What is their function?
- 3 muscles that lie in the palm at the base of the little finger
- Make up the ‘hypothenar eminence’
- Move the little finger (mirror the thenar eminence muscles)
What are the hypothenar muscles innervated by?
By the deep branch of the ulnar nerve
How many muscles make up the ‘lumbrical’ muscle group? Where do the lumbricals arise from?
- 4
- Don’t have a bony attachment but instead arise from the tendons of the flexor digitorum profundus
- FDP gives off 4 tendons in the palm
How many muscles make up the ‘interosseous’ muscle group? Where do they lie?
- 7
- 3 in the palm
- 4 in the dorsum
- These lie between adjacent metacarpal bones
What are the lumbricals innervated by?
The lateral two lumbricals (of the index and middle fingers) are innervated by the median nerve. The medial two lumbricals (of the little and ring fingers) are innervated by the ulnar nerve.
What are the interossei muscles innervated by?
The ulnar nerve
Where does adductor pollicis lie? What is its action?
A single muscle that lies in the palm and adducts the thumb
What is adductor pollicis innervated by?
The ulnar nerve
What intrinsic muscles of the hand does the ulnar nerve innervate?
- Hypothenar muscles
- Interossei muscles
- Medial 2 lumbrical muscles (4th and 5th digits)
- Adductor pollicis
What intrinsic muscles of the hand does the median nerve innervate?
- Thenar muscles
- Lateral 2 lumbrical muscles (2nd and 3rd digits)
Does the radial nerve innervate any intrinsic muscles of the hand?
No
What are the muscles of the ‘thenar’ eminence?
- Opponens pollicis
- Flexor pollicis brevis
- Abductor pollicis brevis
What muscle of the thenar eminence is the largest? Which lies the deepest?
The opponens pollicis is the largest of the thenar muscles, and lies underneath the other two.
Where do the muscles of the thenar eminence originate?
From the carpal bones (centered on the trapezium)
What is the trapezium?
The trapezium bone is a carpal bone in the hand
What is the action of opponens pollicis brevis?
Opposes the thumb, by medially rotating and flexing the metacarpal on the trapezium.
Where does opponens pollicis brevis insert?
On the 1st metacarpal
Action of abductor pollicis brevis?
Abducts the thumb.
Where does abductor pollicis brevis insert?
Attaches to the base of the proximal phalanx of the thumb.
Action of flexor pollicis brevis?
Flexes the metacarpophalangeal (MCP) joint of the thumb.
Where does flexor pollicis brevis insert?
Attaches to the base of the proximal phalanx of the thumb.
Describe relation of flexor and abductor pollicis brevis
Flexor pollicis brevis lies slightly more medially
Abductor pollicis brevis lies slightly more laterally
Both lie superficial to the opponens pollicis
Name the highlighted muscle
Flexor pollicis brevis
Name the muscle highlighted in blue
Abductor pollicis brevis
What nerve is being pointed to? What type of nerve is this?
Recurrent branch of the median nerve - motor nerve
This prosection provides a deep view of the thumb. What muscle is highlighted in pink?
Opponens pollicis (lies deep to abductor)
What are the names of the 3 muscles of the hypothenar eminence?
- Opponens digiti minimi
- Abductor digiti minimi
- Flexor digiti minimi brevis
N.B. the names of the thenar muscles have just been replaced with ‘digiti minimi’
Where do the hypothenar eminence muscles originate?
Carpal bones (centered on the hamate and pisiform)
Describe locations of the 3 hypothenar muscles?
ODM - lies deep to the others
ADM - most superficial
FDM - lies laterally to the ADM
Where does opponens digiti minimi insert?
On the 5th metacarpal (shown in diagram with opposing thenar muscle)
Action of ODM?
It rotates the metacarpal of the little finger towards the palm, producing opposition.
Where does abductor digiti minimi insert?
It attaches to the base of the proximal phalanx of the little finger (5th digit)
(shown in diagram with opposing thenar muscle)
What is movement of ADM?
Abducts the little finger.
Where does the flexor digiti minimi insert?
Inserts into the base of the proximal phalanx of the little finger (same as ADM)
(shown in diagram with opposing thenar muscle)
Action of FDM?
Flexes the MCP joint of the little finger.
Difference in innervation between thenar and hypothenar muscles?
Thenar - recurrent branch of median nerve
Hypothenar - deep branch of ulnar nerve
Name the highlighted muscles
Prosection is palm side nearest little finger
Blue - ADM
Orange - FDM
Pink - ODM
What nerve is being pointed to?
Deep branch of the ulnar - motor nerve
What is the movement of adductor pollicis?
Adducts the thumb (i.e. helps to draw thumb back towards the hand)
Origin of adductor pollicis?
This is a large triangular muscle with 2 heads.
One head originates from metacarpal III. The other head originates from the capitate and adjacent areas of metacarpals II and III.
What happens when the muscle fibres of the adductor pollicis contract?
They pull the proximal phalanx of the thumb towards the midline (towards middle finger) –> this has effect of drawing thumb in (adduction)
Difference between innervation of the thenar muscles and adductor pollicis?
Thenar - recurrent branch of median nerve
Adductor pollicis - deep branch of ulnar nerve
Is there an adductor digiti mimini? What adducts the little finger instead?
No - one of the interosseous muscles adducts the little finger
What are the origins of the lumbricals?
Each lumbrical originates from a tendon of the flexor digitorum profundus
Where do the lumbricals insert?
They travel onto the thumb side (lateral side) of each finger and insert on the base of proximal phalanges and then onto the extensor expansion (on the dorsum of the finger)
Actions of the lumbricals?
Flexion: at the MCP joint
(Contribute to) Extension: at the distal (DIP) and proximal (PIP) interphalangeal joints of each digit
Allow combined move of flexion at MCPJ and extension at DIPJ and PIPJ
What are the lumbricals innervated by?
Dual innervation:
- Lateral 2 lumbricals –> median nerve
- Medial 2 lumbricals –> ulnar nerve
Where are the interossei muscles located? What can they be divided into?
Between the metacarpals –> They can be divided into two groups: the dorsal and palmar interossei
How many interossei muscles are found in the palmar group? How many in the dorsal group?
3 palmar interossei muscles
4 dorsal interossei muscles
Where do the palmar interossei originate?
From a medial or lateral surface of a metacarpal
Where do the palmar interossei insert?
Each insert on the base of proximal phalanges and extensor expansion
What is the movement of the palmar interossei?
- Adducts the fingers at the MCP joint.
- Contributes to flexion at the MCPJs and extension at the PIPJs and DIPJs (via their insertion onto the extensor expansion)
What are the palmar interossei innervated by?
The deep branch of the ulnar nerve
Location of the dorsal interossei?
The most superficial of all dorsal muscles, these can be palpated on the dorsum of the hand.
What is the origin of the dorsal interossei?
Each interossei originates from the lateral and medial surfaces of the metacarpals.
Where do the dorsal interossei insert?
Insert on the base of the proximal phalanges and extensor expansion
What is the action of the dorsal interossei?
- Abduct fingers
- Contribute to flexion at the MCPJs
- Contribute to extension at the PIPJs and DIPJs via their insertion onto the extensor expansion
When the 2nd and 3rd dorsal interossei contract together, what effect does this have on the middle finger?
Effects cancel each other out –> middle finger doesn’t move
Where does each dorsal interossei lie?
Between the metacarpals (e.g. 4th dorsal interosseous muscle lies between 3rd and 4th digit)
What finger does the 4th dorsal interosseous muscle abduct?
The ring finger (sits between 3rd and 4th digit but has NO effect on little finger)
What are the terminal branches of the brachial artery?
The radial and ulnar arteries - they course down the medial and lateral forearm towards the wrist
Where can you palpate the radial pulse?
Where can you palpate the ulnar artery?
What happens when the radial and ulnar arteries reach the palm? What is purpose of this?
They anastamose to form the palmar arches (superficial and deep) –> ensures perfusion of hand should one of these vessels become blocked
What arises from the palmar arteries?
The metacarpal and digital arteries
Which is the only nerve that passes through the carpal tunnel?
The median nerve
Where do the superficial veins (cephalic and basilic) of the upper limb arise?
From dorsum of the hand
What side is the cephalic vein found on? What landmark does it run through?
Dorsal lateral aspect - runs through the ASB and into the lateral forearm
What side is the basilic vein found on?
Dorsal medial aspect
Where is the cephalic vein formed?
In the ASB
How does the basilic vein form the axillary vein?
The basilic vein joins with the deep veins of the arm to form the axilary vein in the axilla
Why is the dorsal venous network important in clinical practice?
IV access - back of hand is common place for cannulation
What does the cephalic vein drain into?
The axillary vein
Normal hand x-ray
Normal carpus x-ray
- 8 carpal bones
- Joint surfaces are smooth and uniform
- It is normal to see some superimposition of the carpal bones on each other
For clinical practice, which carpal bones are particularly important?
Scaphoid - carpal bone that is most commonly fractured
Lunate - carpal bone that is most commonly dislocated
What are the 2 carpal bones that articulate with the radius to form the wrist joint?
Scaphoid and lunate
Labelled carpal bones
Where is the injury in this X-ray?
Which carpal bone articulates with the thumb?
Trapezium
What abnormality can you see here?
What abnormalities can you see?
?
Why must you examine the hand and movements carefully during hand injury?
Have a high index of suspicion for muscle / tendon / nerve injury when there has been an injury to the hand – you must examine the hand and movements carefully. Have a low threshold for referral for further assessment (do not risk missing these injuries).
Where is the injury? What structures are at risk? How can you assess if these structures have been injured?
?
Where is the injury? What structures are at risk? How can you assess if these structures have been injured?
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Where is the injury? What structures are at risk? How can you assess if these structures have been injured?
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Name the structures
Yellow - thenar eminence
Blue - 2 lateral lumbrical muscles
Light blue - carpal tunner
Arrow - route of median nerve
What sensory branches of the median nerve are responsible for innervation of the hand? Where do these branches arise?
Palmar cutaneous branch –> arises in the forearm and travels into the hand (does not pass through capral tunnel)
Palmar digital cutaneous branch –> arises in the hand after the median nerve passes through the carpal tunnel
What do the sensory branches of the median nerve innervate in the hand?
Palmar cutaneous branch –> It innervates the lateral aspect of the palm.
Palmar digital cutaneous branch –> Innervates the palmar surface and fingertips of the lateral three and half digits.
What motor branches of the median nerve are responsible for innervation in the hand?
- Recurrent branch
- Palmar digital branch
What does the recurrent branch and palmar digital branch of the median nerve innervate?
Recurrent - Thenar muscles
Palmar digital - Lateral two lumbricals
If there is an injury to the median nerve at the wrist, what structures are affected?
Structures downstream of the wrist
How do median nerve injuries at the wrist present?
Motor:
- Thenar muscles paralysed
- Atrophy (wasting) and weakness of the thumb
- Lateral 2 lumbricals paralysed
Sensory:
- Sensory disturbance (e.g. pain, diminished sensation, pins and needles) in the distribution of the median n.
What branch of the ulnar nerve innervates the majority of the intrinsic hand muscles?
The deep branch of the ulnar nerve
Motor function of deep branch of ulnar nerve?
Innervates:
- Hypothenar muscles (a group of muscles associated with the little finger)
- Medial two lumbricals
- Adductor pollicis
- Palmar and dorsal interossei of the hand
- Palmaris brevis
How does the ulnar nerve provide sensory innervation of the hand? Where do these branches arise?
Via 3 branches:
- Palmar cutaneous branch –> arises in forearm and travels into hand
- Dorsal cutaneous branch –> arises in forearm and travels into hand
- Superficial branch –> arises in hand itself
What do the 3 sensory branches of the ulnar nerve innervate?
Palmar cutaneous branch – innervates the medial half of the palm.
Dorsal cutaneous branch – innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
Superficial branch – innervates the palmar surface of the medial one and a half fingers.
How do ulnar nerve injuries at the wrist present?
Motor:
- 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:
- The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected. This results in sensory loss over palmar side of medial one and a half fingers only.
What is ‘claw hand’? What is it caused by?
Abnormal attitude of the hand that develops due to ulnar nerve damage causing paralysis of the lumbricals.
What features characterise ‘claw hand’?
- Hyperextension of MCP joints of 4th and 5th
- Flexion at PIP and DIP joints of 4th and 5th
- Guttering between the metacarpals
How many lumbricals are found in the hand?
4 - each associated with a finger
Why are the lumbricals crucial to finger movements?
Link the extensor tendons to the flexor tendons –> Denervation of these muscles is the basis for the ulnar claw and hand of benediction.
Where does each lumbrical originate from? Where do they attach?
From a tendon of the flexor digitorum profundus, pass dorsally and laterally around each finger, insert into the extensor expansion
What is the action of the lumbricals?
Flexion at the MCPJ and extension at the IPJs (proximal and distal) of each digit
What is the innervation of the lumbricals?
Lateral 2 (thumb side) –> innervated by the median nerve
Medial 2 (little finger side) –> innervated by the ulnar nerve
