Wrist & Hand

Question 1

What movements occur at the radioulnar joints? Which muscles are involved? Which nerves are involved?

Answer 1

Pronation (median n.):

1. Pronator teres
2. Pronator quadratus

Supination:

1. Supinator (radial n.)
2. Biceps brachii (musculocutaneous n.)

Question 2

What do holes in the raised ridges of bone represent?

Answer 2

Where arteries and veins come in and out of bone as bones have a huge blood supply

Question 3

Where are the radial and ulnar styloid? What does it suggest if they are deformed?

Answer 3

Radial styloid = LATERAL
Ulnar styloid = MEDIAL

Deformity can suggest wrist fracture

Question 4

What is the overall osteology structure of the hand?

Answer 4

From wrist to finger tips:

• Bones: carpal -> metacarpal -> phalanges (usually 3x but thumb only has 2x)
• Joints: carpometacarpal -> MCP (knuckle) -> PIP -> DIP

Question 5

What is the pneumonic for the hand bones?

Answer 5

Looking at R hand palmar side moving from thumb to little finger:

Some - Scaphoid
Lovers - Lunate
Try - Triquestral
Positions - Pisiform

Then a line above moving from thumb to little finger again:

That - Trapezium
They - Trapezoid
Cant - Capitate
Handle - Hamate

Question 6

What type of bone is the pisiform?

Answer 6

Sesamoid bone (like patella) so it can move around

Question 7

What should the ulnars articulation with the carpal bones look like on an image?

Answer 7

Like a space as there is an articular fibrocartilaginous disc present there

Question 8

What bony prominence can be felt between extensor compartments 2 and 3? What can this be an important landmark for?

Answer 8

Dorsal radial tubercle - just distally and medially to this there is a soft spot which is the wrist aspiration point

Question 9

What is the radiocarpal joint?

Answer 9

Condyloid synovial wrist joint that is the articulation of the distal radius with the scaphoid, lunate and triquetrum with 2 planes of movement:

• Flexion/extension
• Adduction/abduction

You CANNOT rotate your wrist, you circumduct it combining these 2 planes of movement

Question 10

What are the 2 strong lateral ligaments of the wrist joint?

Answer 10

1. Medial collateral: ulnar styloid to triquetrum

2. Lateral collateral: radial styloid to scaphoid

Question 11

How can you fracture the waist of the scaphoid? What are the consequences of this?

Answer 11

By falling onto your hand - this will result in tenderness in anatomical snuffbox and possible avascular necrosis (AVN) as the scaphoid unidirectional blood supply runs from distal to proximal (like femoral head) so the proximal section of scaphoid can become necrotic following a fracture which is very problematic as the wrist joint is affected which would greatly impair movement of hand so monitor and fixate these properly

Question 12

What are some other examples of regional fractures that occur in and around the hand?

Answer 12

1. Colle’s: dorsal displacement of wrist due to FOOSH normally
2. Smith’s: ventral displacement of wrist i.e. opposite of Colle’s
3. Bennett’s: proximal metacarpal 1 i.e. thumb often due to skiing accidents when thumb has been on outside of skiing pole (all fingers should be wrapped round together to avoid this)

Question 13

What is the anatomical snuffbox?

Answer 13

A small triangular area on the lateral side of dorsal hand bordered by:

1. Extensor pollucis longus (EPL) medially
2. Extensor pollucis brevis (EPB) and adductor pollucis (AP) laterally
3. Radial styloid proximally

Question 14

What structures pass the anatomical snuffbox and therefore can be palpated here?

Answer 14

Radial artery
Superficial (cutaneous) branch of radial n.
Cephalic (houseman’s) vein
Scaphoid (tenderness here can indicate scaphoid #)

Question 15

Why can cannulation of the cephalic vein at the anatomical snuffbox cause paraesthesia?

Answer 15

Because the vein runs alongside the superficial (cutaneous) branch of the radial n. and this nerve is particularly delicate

Question 16

What is palmar aponeurosis?

Answer 16

A tough fibrous layer limiting movement of the palmar skin allowing people to grip onto objects easily without them falling through hand (unlike dorsal hand) and it attaches to the palmaris longus (PL) proximally if the person has this muscle

Question 17

What disorders can affect the resting position of the hand?

Answer 17

1. Dupuytren’s contracture: aponeurotic thickening causing passive flexion of medial digits
2. Stenosing tenosynovitis: inflammation of tendon and synovial sheath causing a narrowing of pulley system causing a passive flexion of the affect digit (popping sensation if extended)
3. Ulnar claw head: ulnar nerve lesion causing clawing of digits 4 and 5

Question 18

What is the golden rule of hand muscle innervation?

Answer 18

Everything is C8 and T1 supplied and ULNAR nerve supplied EXCEPT

Thenar muscles (innervated by recurrent brunch of median n.)
Lumbricals to digits 2 and 3 

Which are MEDIAN nerve supplied

Question 19

What is the role of intrinsic hand muscles?

Answer 19

Bring about precise control of digit movements and movements such as opposition which allows the thumb pad to encounter pad of other digits allowing you to pick up objects and be dextrous which is important for ADLs

Question 20

What are the 2 eminences of the hand and what do they contain?

Answer 20

1. Thenar
2. Hypothenar

BOTH containing 3 types of muscle:

• Flexor
• Abductor
• Opposer

Question 21

What can lower motor neuron (LMN) damage of the hand muscles cause? Give an example.

Answer 21

Weakness/paralysis, muscle wasting and a changed resting position of digits (can vary depending on hand/wrist position) e.g. thenar eminence wasting as a result of CTS for example, will weaken/paralyse the muscles so the thumb will be extended at rest due to loss of flexor, slightly adducted due to loss of abductor and have an inability to oppose due to loss of opposer - after a while it will begin to waste to the point where you can see bands of muscles and it will start to look like other fingers where pad is facing forward

Question 22

What do the lumbricals do? What is their innervation?

Answer 22

Intrinsic hand muscles passing from deep flexor tendons to extensor expansion where they spread out forming a flat sheath of tendon that flexes the MCP joint and extends the PIP/DIP joints giving the hand a upside down L shape (clawing of digits will occur if these muscles stop working)

Innervation:

• 2 lumbricals on ulnar (medial) side innervated by ulnar n.
• 2 lumbricals on radial (lateral) side innervated by median n.

Question 23

What do the interosseous muscles do? What is their innervation?

Answer 23

Sit between metacarpal bones and flex MCP and extend PIP/DIP like the lumbricals as they insert into extensor expansion but mainly:

• Palmar interossei adduct (PAD): adduction towards middle finger
• Dorsal interossei abduct (DAB): abduct away from middle finger

Ulnar n. innervated

Question 24

How can you test the interosseous muscles?

Answer 24

PAD:
Ask patient to hold piece of paper between 2 fingers to test strength

DAB:
Ask patient to abduct fingers splaying them out and to resist you trying to push them back towards the middle finger

Question 25

What muscles abduct and adduct the thumb? What is their innervation?

Answer 25

Abduct: abductor pollicis brevis (APB) and abductor pollicis longus (APL) Adduct: adductor pollicis (AP)

Question 26

What sign will show if the adductor pollicis muscle stops working?

Answer 26

Froment sign: excess thumb flexion whilst pinching which normally requires thumb adduction - a piece of paper will also easily be able to be pulled out from between the thumb and digit due to weakness

Question 27

What are synovial sheaths? What can go wrong with them?

Answer 27

Sheaths that cover and conjoin the flexor and extensor tendons across the hand and wrist - can be involved in infection spread, ganglion formation (treat with surgery or corticosteroid aspiration) or tenosynovitis because a common flexor sheath called the ulnar bursa extends distally along all digits in most people and through carpal tunnel into proximal forearm

Question 28

What other fascia bound spaces can also get infected in the hand?

Answer 28

Thenar and midpalmar spaces between the deep flexor tendons and metacarpals/interossei in the palm e.g. through splinters and this can spread down the synovial sheaths too and may require surgical drainage if abscess if large enough

Question 29

What is the carpal tunnel?

Answer 29

A tunnel on the anterior (volar) side of hand acting as a passageway for the tendons of the digit flexors passing into the hand from the anterior forearm with the entrance being marked by the distal wrist crease and the tunnel moving between the thenar and hypothenar eminences

Question 30

What forms the carpal tunnel?

Answer 30

Flexor retinaculum covers the roof the tunnel and attaches to carpal bones pisiform, hook of hamate, scaphoid tubercle and trapezium tubercle to form the carpal arch

Question 31

What travels through the carpal tunnel?

Answer 31

Median n. (superficial palmar branch comes off before tunnel and runs superficial to it) 9 tendons: - Flexor digitorum superficialis (FDS) x 4 - Flexor digitorum profundus (FDP) x 4 - Flexor pollicis longus (FPL)

Question 32

What canal does the ulnar nerve run in? Why is this clinically relevant?

Answer 32

Guyon's canal superficially of the carpal tunnel - can become compressed when biking and wrist is pressed against the handle bars causing potentially months weakness of hand muscles e.g. grip weakness and sensory changes on the medial 1.5 digits which can last months if sufficiently compressed

Question 33

What is carpal tunnel syndrome (CTS)? What symptoms and examination findings would you find associated with it?

Answer 33

An inflammation of the carpal tunnel due to excess wrist pressure or overuse compressing the median nerve producing motor and sensory symptoms such as: - Thenar muscle weakness and wasting so thumb opposition (pincer grip) is weakened so patient would be less dextrous - Lumbricals of digits 2 and 3 would also be weakened and wasted - LOS of lateral 3.5 digit tips BUT sensation of lateral plane of PL is SPARED due to palmar cutaneous branch of median n. not passing through carpal tunnel

Question 34

What can cause carpal tunnel syndrome?

Answer 34

``` Anything that occupies excess space: Ganglion cyst Giant cell tumour Neuroma Lipoma Soft tissue thickening (e.g. hypothyroidism and pregnancy) Fluid retention ```

Question 35

How is carpal tunnel treated?

Answer 35

Surgically to decompress and release pressure by cutting through the flexor retinaculum using special equipment as it is so tough

Question 36

What is the cutaneous innervation to the palmar hand and digits?

Answer 36

Ulna nerve: medial 1.5 digits Median nerve: lateral 3.5 digits Radial nerve: dorsal hand connecting lateral 3.5 digits and a very small area at the lateral proximal palm under the thumb anteriorly

Question 37

Where are the digital cutaneous nerves? Why is this? How can this be medically exploited?

Answer 37

Pass along sides of digits as this is where they are least likely to become damaged by cuts for example (why cuts dont often cause sensory loss) - can be locally blocked in the dorsal web space so medics can remove a nail or even a finger

Question 38

How can you test if the median nerve has been compressed e.g. in carpal tunnel syndrome (CTS)?

Answer 38

1. Tinel's test: tap median n. just proximal to carpal tunnel under or lateral to palmaris longus (PL) 2. Phalen's test: hands are placed facing down with dorsal hands pressing against eachother for 30-60 seconds 3. Reverse Phalens: hands in prayer position for 30-60 seconds If +ve, these tests will elicit tingling/painful symptoms in patients in the median n. distribution

Question 39

What is the blood supply to the hand?

Answer 39

Radial and ulnar artery along with interosseous arteries run down to hand. Ulnar artery enters lateral to pisiform bone through Guyon's canal (palpation point) forming the superficial palmar arch (distal extent approx. along palm from thumb web space). Radial artery passes posteriorly through floor of anatomical snuffbox (palpation point), behind thumb and into palm deeply to form the deep palmar arches which anastomose with the superficial arch. Digital arteries come off and run up the sides of the digits to supply them along with the cutaneous nerves.

Question 40

Where can the radial artery be accessed for arterial blood gas (ABG) for example?

Answer 40

Lateral to flexor carpi radialis (FCR) at wrist where the radial pulse is palpable

Question 41

What is Allen's test?

Answer 41

A test that should be performed to test the presence of ulnar artery patency of vascular anomalies in the hand prior to radial artery procedures e.g. cannulation or ABG where you compress both the radial and ulna arteries on both sides of wrist, get patient to make a fit and the hand will then go pale but once you release the ulnar artery, the hand should quickly fill with blood and go red reasonably quickly if there is no blockage of the ulna artery

Question 42

What points on the hand can you test sensation for different nerves?

Answer 42

Ulna: little finger or just below on palm Median: index finger Radial: 1st dorsal interosseous web space

Question 43

Where is the median nerve vulnerable to damage?

Answer 43

It runs superficially before carpal tunnel so a FOOSH can damage it e.g. if glass lacerates the wrist upon falling or if someone attempts suicide by cutting transversely across the wrist (does not usually damage radial artery as its lateral and deeper to FCR tendon and its so painful to cut through it people stop before they reach the artery)

Question 44

What can the radial nerve clinically be used for?

Answer 44

Spare part for grafting

Question 45

Why must you perform the Allen's test before doing an arterial blood gas (ABG) on the radial artery?

Answer 45

When a needle is put into it, the SM around it can contract and spasm so if ulna artery is not anastomotic with the radial and able to supply blood to the hand, problems such as tissue death to parts of hand can occur