L5: The Hand

Question 1

Name the bones and joints of the hand.

Answer 1

Bones include: Distal phalanges, Intermediate phalanges, Proximal phalanges, Metacarpals and carpals.

The joints between them are:

• Carpometacarpal joint
• The Metacarpophalangeal joint
• Interphalangeal joint (in the thumb)
• Proximal interphalangeal joint
• Distal interphalangeal joint

The small joints in the hand are synovial and so can be affected by rhematoid arthritis.

Question 2

What are the possible movements at the digits?

Answer 2

Fingers:

• Abduction - Move fingers out
• Adduction - move fingers back in

[These two usually happen at the axis of the middle finger]

• Extension
• Flexion

Question 3

What are the possible movements at the thumb?

Answer 3

• Abduction
• Adduction
• Flexion
• Extension
• Opposition

Question 4

What are the intinsic muscles of the hand and there actions?

Answer 4

On the palmar surface:

• Thenar eminence:
• Abductor pollicis brevis (most deep) - abducts the thumb
• Flexor pollicis brevis (most medially) - flexes the thumb
• Oppenens pollicis (most laterally) - opposes the thumb

*Hypothenar eminence:
- Abductor digiti minimi
(most deep) - abducts the little finger
- Flexor digiti minimi (most laterally) - flexes the little finger
- Oppenens digiti minimi (most medially) - opposes the little finger

• Lumbrical Muscles - flex the MCP joint and contribute to extension to the PIP joint and DIP joint. Allows for a combination move.
• Palmar interossei muscles - Adduction of the 3rd, 4th and 5th digits.
• Adductor Pollics - adduction of the thumb.

On the dorsal surface:
*Dorsal interossei muscles - abduction of the 4 digits.

Question 5

What are the attachments of the intrinsic muscles of the thenar eminence?

Answer 5

*Thenar eminance:
OP: Inserts on the first metacarpal.
APB: Inserts on the base of the proximal phalanx of the hand.
FPB: Inserts on the base of the proximal phalanx of the hand.
These muscle orginate from the carapl bones - Trapezium.

Question 6

What are the innervations of the intrinisic muscles of the hand?

Answer 6

Thenar eminence: Innervated by the recurrent branch of the median nerve.

Hypothenar eminence: supplied by the deep branch of the ulnar.

Adductor pollicis: Innervated by the deep branch of the ulnar nerve.

Lumbrical muscles: The medial 2 muscles is innervated by the ulnar nerve and the lateral 2 muscles are supplied by the median nerve.

Palmar interossei muscles: supplied by the deep branch of the ulnar.

Dorsal Interossei muscles: supplied by the deep branch of the ulnar.

Question 7

What are the major nerves and vessels of the hand?

Answer 7

Vessel:

- The radial and ulnar arteries are the terminal branches of the brachial. They course down the medial and lateral forearm towards the wrist. We can palpate the radial artery and the ulnar artery.
- The radial and ulnar arteries anastomose in the palm to form the palmar arches. This ensures perfusion of the hand in the case on becomes blocked. Metacarpal and digital arteries arise from these. 

Nerves:
The median and ulnar nerves travel into the hand – only the median travels through the carpal tunnel. The ulnar nerve travels over the carpal tunnel. The radial nerve innervates a prat of skin over the hand. The radial nerve does not supply the intrinsic muscles but does supply an area over the skin by the ASB.

Veins:
- Superficial veins on the dorsum of the hand. (We have deep veins on the hand that follow the arteries.)
- These form the cephalic and basilic veins
- The cephalic vein - on the dorsolateral aspect - formed in the ASB and courses up the lateral forearm towards the cubital fossa.
- The basilic vein is formed on the medial aspect of the forearm and courses up to the cubital fossa. It drains the medial part of the hand.
- The basilic vein joins with the deep veins of the arm to form the axillary vein in the axilla
- The cephalic vein drains into the axillary vein
The dorsal venous network is extremely important clinically as a site for IV cannulation.

Question 8

Name the carpal bones.

Answer 8

From ulna to radius
Proximal row:
Scaphoid, Lunate, Triquetrum and Pisiform

Distal row: Trapezium, Trapezoid, Capitate and Hamate

Question 9

What are the basic principles of examining joint movement in order to identify nerve, tendon or msucle injuried?

Answer 9

-

Question 10

What is the presentation of median nerve injury?

Answer 10

Innervation of the median nerve:

- Thenar eminence 
- Lateral part half of the lumbrical muscles 
- Through the carpal tunnel innervates the sensory branch that innervates the skin on the lateral, around the 3 digits of the hand.

Injuries prevent with loss of movement and eventually atrophy of the thenar eminence. Injury includes carpal tunnel injury.

Question 11

What is the presentation of ulnar nerve injury?

Answer 11

Sensory disturbance e.g. pain, diminished sensation, pins and needles in the distribution of the ulnar nerve.

In claw hand - ulnar nerve injury:
- Hyperextension of MCP joints of 4th and 5th
- Flexion at PIP and DIP joints of 4th and 5th but not at the index or ring finger
Guttering between the metacarpals

Question 12

How can we identify OA and RA on the fracture?

Answer 12

b

Question 13

True/False: All the following intrinsic muscles move the thumb:

• OP
• APB
• FPB
• AP
• Dorsal Interossei

Answer 13

False: The dorsal interossei (1) does not abduct the thumb. It moves the second digit as it inserts distally on the 2nd finger. The thumb has other abductors.

Question 14

What’s the most commonly dislocated carpal bone?

Answer 14

Lunate - this is not common

Question 15

What is the most commonly fractured carpal bone?

Answer 15

Scaphoid