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Musculoskeletal System > Week 6 - The Hand > Flashcards

Week 6 - The Hand Flashcards

0
Q

Which muscles are included in the intrinsic muscle group of the hand?

A
  • Thenar muscles
  • Hypothenar muscles
  • Lumbricals
  • Interossei
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1
Q

What are the 2 groups of muscles that can be found in the hand?

A

Extrinsic: located in the anterior and posterior compartments of the forearm, control crude movements
Intrinsic: located within the hand itself, responsible for the fine motor functions of the hand

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2
Q

What are the thenar muscles?

A

3 short muscles

  • Opponens pollicis (largest muscle, lies underneath the other 2 muscles, from the tubercle of the trapezium and the associated flexor retinaculum to the metacarpal of the thumb)
  • Abductor pollicis brevis (from the tubercles of the scaphoid and trapezium and from the associated flexor retinaculum, to the lateral side of proximal phalanx)
  • Flexor pollicis brevis (from the tubercle of the trapezium and associated flexor retinaculum to the base of the proximal phalanx of the thumb)
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3
Q

What innervates the thenar muscles?

A

Median nerve

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4
Q

What is the action of the opponens pollicis?

A

Opposes the thumb, by medically rotating and flexing the metacarpal on the trapezium

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5
Q

What are the actions of the abductor pollicis brevis?

A

Abducts the thumb

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6
Q

What are the actions of the flexor pollicis brevis?

A

Flexes the MCP joint of the thumb

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7
Q

What are the hypothenar muscles?

A
  • Opponens digiti minimi (from the hook of hamate and associated flexor retinaculum, to the medial margin of metacarpal V)
  • Abductor digiti minimi (from the pisiform and the tendon of the flexor carpi ulnaris, to the base of the proximal phalanx of the little finger)
  • Flexor digiti minimi brevis (from the hook of hamate and adjacent flexor retinaculum, to the base of the proximal phalanx of the little finger)
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8
Q

What innervates the hypothenar muscles?

A

Ulnar nerve

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9
Q

What are the actions of the opponens digiti minimi?

A

Rotates the metacarpal of the little finger towards the palm, producing opposition

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10
Q

What are the actions of the abductor digiti minimi?

A

Abducts the little finger

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11
Q

What are the actions of the flexor digiti minimi brevis?

A

Flexes the MCP joint of the little finger

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12
Q

What are the lumbricals?

A
  • There are 4 lumbricals in the hand
  • Each are associated with a finger
  • They are crucial to finger movement, linking the extensor tendons to the flexor tendons
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13
Q

What innervates the lumbricals?

A
  • Medial 2 lumbricals = ulnar nerve

- Lateral 2 lumbricals = median nerve

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14
Q

What are the interossei muscles?

A
  • Muscles that are located between the metacarpals
  • Can be divided into 2 groups: dorsal and palmar
  • Dorsal: from the medial and lateral surfaces of a metacarpal, to the extensor hood and proximal phalanx of each finger
  • Palmar: from a medial or lateral surface of a metacarpal, to the extensor hood and proximal phalanx of the same finger
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15
Q

What innervates the interossei muscles?

A

Ulnar nerve

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16
Q

What are the actions of the interossei muscles?

A
  • Dorsal: abducts the fingers at the MCP joint (DAB)
  • Palmar: adducts the fingers at the MCP joint (PAD)
  • They also assist the lumbricals in flexion at the MCP joints and extension at the IP joints
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17
Q

What other muscles (I.e. Not intrinsic hand muscles) can be found in the palm?

A
  • Palmaris brevis

- Adductor pollicis

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18
Q

Where is the palmaris brevis found?

A
  • From the palmar aponeurosis and flexor retinaculum

- To the dermis of the skin on the medial margin of the hand

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19
Q

What are the actions of the palmaris brevis?

A
  • Wrinkles the skin of the hypothenar eminence

- Deepens the curvature of the hand, improving grip

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20
Q

What innervates the palmaris brevis?

A

Ulnar nerve

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21
Q

Where does the adductor pollicis originate from/attach to?

A

Has 2 heads:

  • 1 head: from metacarpal III
  • Other head: from adjacent areas of metacarpals II and III, and the capitate
  • Both attach to the base of the proximal phalanx of the thumb
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22
Q

What are the actions of the adductor pollicis?

A

Adducts the thumb

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23
Q

What innervates the adductor pollicis?

A

Ulnar nerve

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24
Q

What is the blood supply to the hand?

A
  • There is a good supply, with many anastomosing arteries
  • Majority are superficial arteries (allows for heat loss when needed)
  • The radial and ulnar arteries interconnect to form 2 arches, from which branches to the digits emerge
  • The radial artery contributes mainly to the supply of the thumb and lateral side of the index finger
  • The ulnar artery contributes mainly to supply of the rest of the digits and medial side of the index finger
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25
Q

How does the ulnar artery enter the hand?

A
  • It moves into the hand anteriorly to the flexor retinaculum and laterally to the ulnar nerve
  • It then divides into 2 branches: superficial palmar arch and deep palmar arch
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26
Q

Where is the superficial palmar arch found?

A
  • Anterior to the flexor tendons in the hand

- Just deep to the palmar aponeurosis

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27
Q

What arises from the superficial palmar arch?

A

The common digital arteries

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28
Q

How does the radial artery enter the hand?

A
  • It enters dorsally, crossing the floor of the anatomical snuffbox
  • It turns medically and moves between the heads of the adductor pollicis
  • It then anastomoses with the deep palmar branch of the ulnar artery, forming the deep palmar arch
29
Q

What is the carpal tunnel?

A
  • A narrow passageway found on the anterior portion of the wrist
  • Serves as the entrance to the palm for several tendons and the median nerve
30
Q

How is the carpal tunnel formed?

A

By 2 layers:
A deep carpal arch
- Concave on the palmar side
- Formed laterally by the scaphoid and trapezium tubercles
- Formed medially by the hook of hamate and the pisiform
Flexor retinaculum
- Thick connective tissue
- Turns the carpal arch into the carpal tunnel by bridging the space between the medial and lateral parts of the arch
- Originates on the lateral side and inserts on the medial side of the carpal arch

31
Q

What are the contents of the carpal tunnel?

A

Tendons:
- Tendon of flexor pollicis longus
- 4 tendons of flexor digitorum profundus
- 4 tendons of flexor digitorum superficialis
Median nerve

32
Q

What happens to the median nerve after it passed through the carpal tunnel?

A

It divides into 2 branches

  • Recurrent branch (supplies the thenar muscles)
  • Palmar digital
33
Q

What does the palmar digital (median) nerve innervate?

A
  • Sensory innervation: the palmar skin and dorsal nail beds of lateral 3.5 digits
  • Motor innervation: lateral 2 lumbricals
34
Q

What is carpal tunnel syndrome?

A

Compression of the median nerve with the carpal tunnel

- It can cause weakness and atrophy of the thenar muscles if left untreated

35
Q

What can cause carpal tunnel syndrome?

A
  • Thickened ligaments and tendon sheaths

- Most often idiopathic (unknown)

36
Q

How can you test for carpal tunnel syndrome?

A
  • Tap the nerve in the carpal tunnel to elicit pain in median nerve distribution
  • Hold the wrist in flexion for 60 seconds to elicit numbness/pain in median nerve distribution
37
Q

How can you treat carpal tunnel syndrome?

A
  • Use a splint to hold the wrist in dorsiflexion overnight to relieve symptoms
  • If unsuccessful, can use corticosteroid injections in the carpal tunnel
  • In severe cases, surgical decompression of the carpal tunnel may be required
38
Q

What is a Boxer’s fracture?

A

A fracture of the 5th metacarpal neck

  • Usually caused by a clenched fist striking a hard object
  • The distal part of the fracture is displaced posteriorly, producing shortening of the affected finger
39
Q

What is a scaphoid fracture?

A
  • Most common carpal bone fracture
  • Causes pain and tenderness in the anatomical snuffbox
  • Needs to be fixed quickly, since it may cut off the blood supply to the proximal part of the bone (will cause a vascular necrosis)
  • If undiagnosed, patient is likely to develop wrist arthritis
40
Q

What is the effect of a superficial laceration at the wrist?

A

May damage the palmar cutaneous branch of the median nerve
- Hence loss of sensation over the skin overlying the thenar eminence
- No motor deficit
Mainly damages skin
No penetration of major blood vessels

41
Q

What are the effects of a deep laceration at the wrist?

A
  • Ulnar nerve damage (results in claw hand deformity, sensory loss in medial 1.5 digits only)
  • Median nerve and its palmar cutaneous branch injury (results in ape thumb deformity, sensory loss on lateral palm and in the lateral 3.5 digits)
  • Tendons in carpal tunnel may be damaged
  • Radial and ulnar artery may be damaged
42
Q

What is the effect of a laceration to the palm?

A
  • May damage tendons
  • Superficial or/and deep artery arches may be damaged depending on depth of wound
  • Median/ulnar nerve damage
43
Q

How can Erb’s palsy occur?

A

Excessive increase in the angle between the neck and the shoulder

  • This stretches (or can even tear) the nerve roots, causing damage
  • Can occur as a result of a difficult birth or shoulder trauma
44
Q

What nerves are affected in Erb’s palsy?

A
  • Musculocutatneous
  • Axillary
  • Suprascapular
  • Subclavian
45
Q

Which muscles are paralysed in Erb’s palsy?

A
  • Supraspinatus
  • Infraspinatus
  • Subclavius
  • Biceps brachii
  • Brachialis
  • Coracobrachialis
  • Deltoid
  • Teres minor
46
Q

Which motor functions are affected in Erb’s palsy?

A

Movements that are lost or greatly weakened:

  • Abduction at shoulder
  • Lateral rotation of arm
  • Supination of forearm
  • Flexion at shoulder
47
Q

Which sensory functions are affected in Erb’s palsy?

A

There is a loss of sensation down the lateral side of arm

48
Q

What is the characteristic presentation of Erb’s palsy?

A

Affected limb hangs limply - “waiter’s tip”:

  • Medially rotated by unopposed actin of the pectoralis major
  • Forearm is pronated due to the loss of biceps brachii
49
Q

What type of injury is Erb’s palsy?

A

An upper brachial plexus injury

50
Q

What is Klumpke’s palsy?

A

A lower brachial plexus injury

51
Q

How can Klumpke’s palsy occur?

A

By excessive abduction of the arm

- E.g. Someone catching a branch of the arm

52
Q

Which nerves are affected by Klumpke’s palsy?

A

Nerves derived from the T1 root

- Ulnar and median

53
Q

Which muscles are paralysed by Klumpke’s palsy?

A

All of the small muscles of the hand

54
Q

What is the sensory effect of Klumpke’s palsy?

A

Loss of sensation along medial side of arm

55
Q

What is the characteristic presentation of Klumpke’s palsy?

A

Clawed appearance of hand

- The MCP joints are hyperextended and the IP joints are flexed

56
Q

What is the most common way of damaging the ulnar nerve at the elbow?

A

Fracture of the medial epicondyle

57
Q

What is the effect on motor functions following ulnar nerve injury at the elbow?

A

Paralysed muscles: flexor carpi ulnaris, medial half of flexor digitorum profundus, interossei, medial 2 lumbricals

  • Flexion of the wrist can still occur, but is accompanied by abduction
  • Abduction and adduction of the fingers cannot occur since interossei muscles are paralysed
  • Movement of the little and ring fingers is greatly reduced, due to paralysis of the medial 2 lumbricals
58
Q

Which sensory functions are affected following ulnar nerve injury at the elbow?

A

All sensory branches are affected

- Loss of sensation over the areas that the ulnar nerve innervates

59
Q

What is a sign of ulnar nerve injury at the elbow?

A

Patient cannot grip paper placed between fingers

60
Q

How can ulnar nerve injury at the wrist occur?

A

Laceration at the wrist

61
Q

Which motor functions are affected following ulnar nerve damage at the wrist?

A
  • The interossei are paralysed, so abduction and Adduction of the fingers cannot occur
  • Movement of the little and ring fingers is greatly reduced, due to paralysis of the medial 2 lumbricals
62
Q

Which sensory functions are affected following ulnar nerve damage at the wrist?

A
  • The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected
  • Sensory loss over palmar side of medial 1.5 fingers only
63
Q

What is a characteristic sign of ulnar nerve damage at the wrist?

A

Patient cannot grip paper placed between fingers

  • For long term cases: a hand deformity called ulnar claw develops
  • – Hyperextension of the MCP joints of the little and ring fingers (due to paralysis of the medial 2 lumbricals and the now unopposed action of the extensor muscles)
  • – Flexion at the IP joints
64
Q

How can median nerve injury occur at the wrist?

A

Commonly in lacerations just proximal to the flexor retinaculum

65
Q

What motor functions are affected following median nerve injury at the wrist?

A
  • Thenar muscles are paralysed
  • Lateral 2 lumbricals are paralysed
  • This affects opposition of the thumb and flexion of the index and middle fingers
66
Q

What sensory functions are affected following median nerve injury at the wrist?

A

Lack of sensation over the area that the median nerve innervates

67
Q

What is the characteristic sign of median nerve injury at the wrist?

A
  • The thenar eminence is wasted, due to atrophy of the thenar muscles
  • If the patient tries to make a fist, only the little and ring fingers can flex completely
  • This results in a characteristic shape of the hand known as ‘hand of benediction’
68
Q

How can median nerve injury occur at the elbow?

A

Commonly by supracondylar fracture of the humerus

69
Q

Which motor functions are affected following median nerve injury at the elbow?

A
  • The flexors and pronators in the forearm are paralysed, with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus
  • The forearm is constantly supinated
  • Flexion is weak (often accompanied by adduction, because of the pull of the flexor carpi ulnaris)
  • Flexion at the thumb is also prevented, as both the longus and brevis are paralysed
  • The lateral 2 lumbrical muscles are paralysed
  • The patient will not be able to flex at the MCP joints or extend at the IP joints of the index and middle fingers
70
Q

What are the characteristic signs of median nerve injury at the elbow?

A
  • Wasted thenar eminence

- Hand of benediction

Musculoskeletal System (12 decks)

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