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Ebopras > Hand Anatomy/ Embryology > Flashcards

Hand Anatomy/ Embryology Flashcards

1
Q

What tissues comprise the limb bud?

A

Mesenchyme covered by ectoderm. The limbs grow by proliferation of mesenchyme.

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2
Q

Which genes regulate patterning in limb development?

A

Homeobox-containing (HOX ) genes.

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3
Q

When do the limb buds first appear?

A

Toward the end of the fourth week of development, at which time a group of mesenchymal cells in the lateral
mesoderm are activated. The buds are visible by day 26 to day 27.

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4
Q

When is the critical period for upper limb development?

A

Twenty-four to thirty-six days after fertilization.

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5
Q

When are finger buds visible?

A

The end of week 6.

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6
Q

When does ossification occur?

A

Between weeks 8 and 12, ossification of the cartilaginous framework occurs. Epiphyses gradually ossify until the
termination of puberty.

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7
Q

What are the last bones to ossify within their cartilaginous framework?

A

The carpal bones in which ossification begins during the first year of life.

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8
Q

Does sensory or motor innervation occur first?

A

Sensory axons enter the limb after motor axons and use these for guidance.

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9
Q

When is nervous system myelination completed?

A

Around 2 years of age.

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10
Q

What is responsible for proximodistal development?

A

The apical ectodermal ridge (AER), which expresses endogenous fibroblast growth factors.

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11
Q

What is responsible for radioulnar development?

A

The zone of polarizing activity, found in the posterior margin of the limb bud, and activated by fibroblast growth
factors from the AER that cause Sonic hedgehog (SHH) gene expression.

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12
Q

What is responsible for dorsoventral development?

A

Expression of WNT7 and engrailed-1 (EN1) from the dorsal and the ventral epidermis, respectively.

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13
Q

What process is responsible for syndactyly occurrence?

A

Apoptosis, likely mediated by bone morphogenic proteins signaling TGF-􏰁.

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14
Q

How common is syndactyly and which digits are most commonly affected?

A

Occurs in one in 2,200 births, most commonly affecting the webspace between the middle and ring fingers.

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15
Q

Which arteries supply the limb buds?

A

Dorsal intersegmental arteries arising from the aorta.

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16
Q

Outline the American Society for Surgery of the Hand classification of congenital deformities of the hand.

A

The original classification scheme was proposed by Swanson:
i. Failure of formation
ii. Failure of differentiation
iii. Duplication iv. Overgrowth
v. Undergrowth
vi. Constriction band syndromes
vii. Generalized anomalies and syndromes

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17
Q

What is the anatomic snuffbox?

A

The area bounded by the tendons of the abductor pollicis longus and extensor pollicis brevis anteriorly and the tendon of the extendor pollicis longus posteriorly. The floor is formed by the scaphoid and trapezium, and it is a frequent site of tenderness after scaphoid fracture

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18
Q

Where is the metacarpophalangeal (MCP) joint relative to the MCP palmar flexion crease?

A

Proximal.

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19
Q

What is the “fixed unit” of the hand?

A

The distal carpal row and second and third metacarpals.

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20
Q

What is a felon?

A

A subcutaneous abscess of the distal digital pulp. It involves the septal compartments and causes compartment
syndrome of the distal phalangeal pulp. If the pad is not involved, then it is an “apical infection” instead.

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21
Q

What is the normal value for moving two-point discrimination of the fingertip?

A

2 to 3 mm, with best discrimination occurring in individuals in their 20s and in ulnar sided digits. A score of 7 out of 10 correct answers determines the value of two-point discrimination.

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22
Q

What is the perionychium? Paronychium? Hyponychium? Eponychium? Lunula?

A

The perionychium includes the nail bed, nail fold, eponychium, paronychium, and hyponychium. The paronychium is the skin on either side of the nail bed. The hyponychium is skin distal to the nail bed. The eponychium is the skin proximal to the nail that covers the nail fold. The white arc in the proximal nail is the lunula and is the distal extent of the germinal matrix. Distal to this is the sterile matrix

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23
Q

Which tissues contribute to nail growth?

A

The germinal matrix produces approximately 90% of the nail, while the sterile matrix adds a thin layer of cells
underneath the nail to ensure its adherence.

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24
Q

What is a paronychia?

A

Acute paronychia is infection of the paronychial tissues.

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25
Q

How long does a nail take to grow?

A

Approximately 6 months.

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26
Q

Name the median innervated intrinsic muscles of the hand.

A

The intrinsic muscles of the hand are innervated by the ulnar nerve, except the radial two lumbricals, opponens
pollicis, abductor pollicis brevis, and superficial head of the flexor pollicis brevis

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27
Q

What are the functions of the palmar and dorsal interossei?

A

The interossei originate from the metacarpal shafts and form the lateral bands, aiding in the function of the lumbrical muscles. In addition, the Palmar interossei ADduct the fingers and the Dorsal interossei ABduct the fingers

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28
Q

Name the thenar muscles. What order are they in?

A

Superficial to deep, they are:
abductor pollicis brevis
flexor pollicis brevis
opponens pollicis
adductor pollicis

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29
Q

Name the hypothenar muscles.

A

Palmaris brevis
Abductor digiti minimi
Flexor digiti minimi brevis r Opponens digiti minimi

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30
Q

Name the muscles of the mobile wad.

A

Brachioradialis, extensor carpi radialis brevis, extensor carpi radialis longus.

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31
Q

How can you test for extensor pollicis longus (EPL) function?

A

Ask the patient to rest their hand palm down on a table and lift the thumb—only the EPL can move lift the thumb
dorsal to the plane of the palm.

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32
Q

What are Cleland’s and Grayson’s ligaments?

A

Cleland’s ligaments connect the digital fascia to the sides of the phalanges and are not involved in Dupuytren disease. They lie dorsal to the neurovascular bundle. Grayson’s ligaments connect the tendon sheath to the digital fascia and are often involved in Dupuytren disease. They lie volar to the neurovascular bundle.

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33
Q

What are natatory ligaments?

A

This is another name for the superficial transverse metacarpal ligaments and these help to create the webspaces.
These coalesce distally with the spiral bands and may be involved in Dupuytren’s disease.

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34
Q

What are the boundaries and contents of the carpal tunnel?

A
  1. Roof: transverse carpal ligament 4. Ulnar border: pisiform and hamate
  2. Floor: carpal bones 5. Contents: the median nerve and nine tendons
  3. Radial border: scaphoid and trapezium
    (flexor digitorum superficialis [FDS], flexor digitorum profundus [FDP], and flexor pollicis longus [FPL])
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35
Q

What are the boundaries and contents of Guyon’s canal?

A
  1. Roof: volar carpal ligament and pisohamate ligament
  2. Floor: transverse carpal ligament
  3. Ulnar wall: pisiform
  4. Contents: ulnar nerve and artery
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36
Q

What is the oblique retinacular ligament?

A

A ligament running between the flexor tendon sheath at the proximal phalanx and the terminal extensor tendon, linking flexion and extension between the interphalangeal joints.

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37
Q

What is the transverse retinacular ligament?

A

They are ligaments that span the edge of the flexor tendon sheath to the conjoined lateral bands, preventing dorsal
shift of the lateral bands, and thus preventing a swan neck deformity

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38
Q

What are the pulleys? What do they do? How many pulleys are there? Which pulleys are the most important?

A

Thickened areas of the synovial sheath. They prevent bowstringing of the flexor tendons. There are five annular and four cruciate pulleys in each of the fingers and two annular and one oblique pulley in the thumb. A2, A4, and the oblique pulleys are essential to prevent bowstringing

39
Q

What is a boutonniere deformity?

A

PIP hyperflexion with DIP hyperextension, which may be caused by extensor mechanism injury, synovitis, or
iatrogenic causes.

40
Q

What is a swan neck deformity?

A

PIP joint hyperextension with DIP joint flexion, which may be due to multiple potential causes including FDS loss,
synovitis, mallet deformity, or iatrogenic causes.

41
Q

Name the seven potential spaces and two bursae in the hand.

A
  1. thenar space
  2. midpalmar space
  3. hypothenar space
  4. interdigital webspace
  5. dorsal subcutaneous space 6. dorsal subaponeurotic space 7. Parona’s space
    In addition to the above, the radial and ulnar bursae.
42
Q

What is a collar button abscess?

A

A webspace abscess in which infection tracks both volarly and dorsally. These infections usually start on the volar surface but dense attachments of the palmar fascia to the skin limit the volar extension causing it to track dorsally forming an hourglass shape.

43
Q

What is a horseshoe abscess and why does it occur?

A

This is an abscess formed by communication or rupture between the ulnar and the radial bursae of the hand through Parona’s space (region between FPL, FDP, and pronator quadratus).

44
Q

What is the ultimate result of an untreated compartment syndrome?

A

Decreased capillary perfusion pressure leads to tissue necrosis and ultimately may result in a Volkmann’s contracture.

45
Q

What are Kanavel’s signs?

A

These are used to diagnose infectious tenosynovitis:
1. Pain and tenderness along the course of the tendon 2. Flexed resting posture
3. Uniform and symmetric swelling
4. Pain on passive extension

46
Q

What is the safe position for splinting the hand and why?

A

The intrinsic plus or safe position: the metacarpophalangeal joints are flexed to 60◦ to 70◦, the interphalangeal joints are fully extended, the wrist is at 10◦ less than maximal extension, and the thumb is abducted. Owing to the nature of the cam of the joint, the collateral ligaments of the metacarpophalangeal joints are maximally stretched when the joint is fully flexed and of the interphalangeal joints are maximally stretched when the joint is fully extended

47
Q

Which is the most mobile carpometacarpal (CMC) joint?

A

The first CMC joint.

48
Q
A
49
Q
A
50
Q
A
51
Q
A
52
Q
A
53
Q

Where are the epiphyses in the bones of the hand?

A

Proximally on all phalanges and the thumb metacarpal, and distally on the other metacarpals.

53
Q

What extensor compartments is Lister’s tubercle between?

A

The second and third extensor compartments.

53
Q

What is a Seymour fracture?

A

A juxtaepiphyseal fracture of the terminal phalanx of the finger. The terminal tendon is attached to the proximal
epiphyseal fragment, and the profundus tendon, attached to the distal fragment, causes it to flex.

53
Q

What is an extra octave fracture?

A

A Salter–Harris 2 fracture of the proximal phalanx of the small finger with ulnar angulation of the small finger.

53
Q

What is a jersey finger fracture?

A

Traumatic avulsion of the flexor digitorum profundus tendon.

53
Q

What is a boxer’s fracture?

A

Metacarpal neck fractures of the ulnar digits.

53
Q

Name the types of mallet injuries.

A

Type I : closed with tendon rupture
Type II: laceration
Type III: abrasion with tissue loss Type IV: with fracture

54
Q

What is a Stener lesion?

A

This occurs in ulnar collateral ligament injury in the thumb when the adductor aponeurosis interposes between the
distally avulsed ligament and its insertion into the base of the proximal phalanx

55
Q

What are the origins and insertions of the lumbrical muscles? What is their function?

A

Originate from the flexor digitorum profundus tendons and insert into the radial aspect of the extensor mechanism distal to the metacarpophalangeal joint. They help flex the metacarpophalangeal joint and extend the interphalangeal joint.

56
Q

What prevents profundus tendons from retracting fully when cut?

A

They may be tethered by the lumbricals, vinculae, and adjacent tendons (with which they share a muscle belly).

57
Q

How are the flexor tendons arranged in the carpal tunnel?

A

The FDP tendons lie on the floor side by side. The FDS tendons to the ring and middle fingers are superficial to
the index and small fingers. FPL lies radially.

58
Q

How often is the palmaris longus tendon present?

A

Between 7% and 20% of people do not have a palmaris longus.

59
Q

What is Camper’s chiasm?

A

This is where the FDS slips that have bifurcated (to allow passage of the FDP tendon) come back together and rejoin on the volar surface of the middle phalanx. Proximal to this location, the profundus tendon is deep to the superficialis tendon.

60
Q

How is the FDP to the index finger unique?

A

It has an independent muscle belly.

61
Q

How do flexor tendons receive nutrition?

A

They receive nutrition through the parietal paratenon, bony insertions, muscle bellies, and the longitudinal vincular system on the dorsal aspect of the tendon—including the vinculum brevis superficialis, vinculum brevis profundus, vinculum longum superficialis, and vinculum longum profundus

62
Q

What are the flexor tendon zones

A

Zone 1: distal to FDS insertion
Zone 2: from the A1 pulley to FDS insertion
Zone 3: from the distal edge of the carpal ligament to the proximal edge of the A1 pulley Zone 4: the carpal tunnel
Zone 5: proximal to the carpal tunnel

63
Q

Name the insertions of the extrinsic extensors.

A

The base of the proximal, middle, and distal phalanges.

64
Q

Name the extensor tendon zones

A

Zone I: distal interphalangeal joint
Zone II: middle phalanx
Zone III: proximal interphalangeal joint (metacarpophalangeal joint in thumb) Zone IV: proximal phalanx (metacarpal in thumb)
Zone V: metacarpophalangeal joint (carpometacarpal join in thumb)
Zone VI: metacarpal
Zone VII: dorsal retinaculum/carpal bones
Zone VIII: distal forearm
Zone IX: mid and proximal forearm

65
Q

How many dorsal extensor compartments are there at the wrist? What are their contents?

A
  1. APL, EPB
  2. ECRL, ECRB 3. EPL
  3. EDC, EIP 5. EDM
  4. ECU
66
Q

Which digits have their own unique extensor tendons? Where are these located?

A

The index and small fingers each have proprius tendons (EIP and EDM) that typically lie both ulnar and volar to their EDC tendons. The EIP tendon typically has a more distal muscle belly than its EDC counterpart.

67
Q

What is a juncturae tendinae?

A

Connections between the common extensor tendons that prevent independent finger extension.

68
Q

What is the primary metacarpophalangeal joint extensor?

A

The extrinsic system, while the intrinsic system is its primary flexor.

69
Q

Name the vascular arches in the hand.

A
  1. Superficial palmar arch (anastomosis between the ulnar artery and the superficial branch of the radial artery). 2. Deep palmar arch (extension of the radial artery after giving off the princeps pollicis artery).
  2. Dorsal carpal arch (anastomosis of the radial and ulnar dorsal carpal branches).
70
Q

Where do digital arteries originate?

A

Common digital arteries originate from the superficial palmar arch.

71
Q

How can radioulnar anastomosis be tested?

A

An Allen’s test is used—the ulnar and radial arteries are occluded by the examiner, blood is removed from the hand
by making a fist, and each artery is released in turn to test patency.

72
Q

Why may an upper arm tourniquet not sufficiently prevent bleeding in the hand?

A

Blood may be shunted via nutrient vessels present in the humerus. A tourniquet should be placed as high as possible
to avoid this.

73
Q

What is the dominant vascular supply to the hand?

A

Most commonly the ulnar artery—66% ulnar artery, 30% radial artery, and 4% persistent median artery.

74
Q

Which are the dominant proper digital arteries for each digit?

A
  1. thumb and index: ulnar digital artery
  2. middle and ring: codominance
  3. small finger: radial digital artery
75
Q

Name the draining lymphatic beds of the arm.

A

Axillary, supraclavicular, and infraclavicular.

76
Q

Between which musculotendinous structures is the radial artery located at the wrist and distal forearm?

A

Between the brachioradialis and the flexor carpi radialis.

77
Q

Between which musculotendinous structures is the posterior interosseous artery located in the forearm?

A

Between extensor carpi ulnaris and extensor digiti minimi.

78
Q

Where does the motor branch of the median nerve arise within the carpal tunnel?

A

Around half are extraligamentous, approximately 30% subligamentous, and approximately 20% transligamentous.

79
Q

Where is the palmar branch of the median nerve found?

A

This sensory nerve arises approximately 6 cm proximal to the transverse carpal ligament between FCR and palmaris longus and running distally along on radial aspect of the carpal tunnel. Overly radial placement of a carpal tunnel release incision may cause injury to this nerve.

80
Q

What does the anterior interosseous nerve supply? What does the posterior interosseous nerve supply?

A

The anterior is a branch of the median nerve supplies FPL, FDS to middle/long fingers, and pronator quadratus. The posterior is a branch of the radial nerve and supplies ECRB, EDC, EDM, ECU, supinator, APL, EPL, EPB, and EIP.

81
Q

Which nerve supplies the flexors of the hand and wrist?

A

The median nerve supplies all flexors except the flexor carpi ulnaris and flexor digitorum profundus to the ring and
small fingers (which are supplied by the ulnar nerve).

82
Q

Are digital nerves dorsal or volar to digital arteries?

A

Volar.

83
Q

List the Sunderland classification of nerve injuries.

A

Grade I is a neurapraxia (the axon is preserved with altered conduction).
Grade II is an axonotmesis (the axonal integrity is disrupted).
Grade III is neurotmesis (disruption of supporting structures) with preservation of the perineurium. Grade IV is neurotmesis with preservation of the epineurium.
Grade V is complete transaction of the nerve trunk.
Grade VI (MacKinnon modification) is a mixed injury.

84
Q

What is a Riche–Cannieu anastomosis?

A

An communication between the deep branch of the ulnar nerve and the recurrent motor branch of the median
nerve in the palm.

85
Q

What is a Martin–Gruber anastomosis?

A

An communication of motor fibers from the median to ulnar nerve in the forearm.

86
Q

Name the possible sites of ulnar nerve compression in ulnar nerve entrapment.

A

These include the following:
1. intermuscular septum (arcade of Struthers, medial septum, medial head of triceps) 2. medial epicondyle
3. epicondylar groove
4. cubital tunnel (between the heads of the flexor carpi ulnaris) 5. flexor–pronator aponeurosis
6. Guyon’s canal

87
Q

Name the possible sites of median nerve compression in pronator syndrome.

A

These include the following:
1. bicipital aponeurosis
2. ligament of Struthers
3. between the heads of pronator teres

88
Q

What is the difference between de Quervain and intersection syndromes?

A

De Quervain syndrome is a stenosing tenosynovitis of the first extensor compartment with pain felt at the wrist, whereas intersection syndrome is caused by the tendons of the first extensor compartment crossing over those of the second compartment and pain is felt proximal to the wrist joint.

Ebopras (22 decks)

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