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Biomechanics > Wrist > Flashcards

Wrist Flashcards

1
Q

What is the waist region?

A

midway bewteen proximal and distal poles of scaphoid

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2
Q

What is the ulnar tilt?

A

25 degrees tilt of the radius (medial direction)

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3
Q

What is the palmar tilt?

A

10 degrees tilt of radius (lateral direction)

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4
Q

The ulnar tilt allows what?

A

wrist and hand to rotate farther into ulnar deviation than into radial deviation

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5
Q

What does the palmar tilt allow?

A

greater amounts of flexion than extension at wrist

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6
Q

What limits radial deviation of the wrist?

A

ulnar tilt and impingement of lateral side of carpus against styloid process of radius

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7
Q

Distal articular surface of radius is what?

A

concave on both ML and AP directions

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8
Q

Where is the transverse carpal ligament connected?

A

pisiform and hamate on ulnar side

tubercles of scaphoid and trapezium on radial side

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9
Q

Palmar side of carpal bones forms what?

A

concavity

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10
Q

What is the carpal tunnel a passageway for?

A

median nerve and tendons of extrinsic flexor muscles of digit

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11
Q

How do the ligaments restrain tendons?

A

they bowstring anteriorly out of carpal tunnel during grasping actions performed with partially flexed wrist

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12
Q

The scaphoid and lunate are lodged between what two rigid structures?

A

distal forearm

distal row of carpal bones

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13
Q

What injuries are the scaphoid and lunate vulnerable to?

A

compression-related injuries

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14
Q

Scaphoid accounts for what percentage of all carpal fractures?

A

60 to 70%

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15
Q

What is the common MOI for a scaphoid fracture?

A

fall on fully supinated forearm with wrist full extended and radially deviated

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16
Q

From where does the scaphoid receive its blood supply?

A

radial artery and branches of anterior interosseous artery

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17
Q

What is retgrade blood flow?

A

proximal ⅓ of bone experiences poor vascular circulation and principally relies

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18
Q

What provides collateral circulation to the scaphoid bone?

A

Dorsal and volar branches of anterior interosseous artery anastomosing with dorsal and volar branches of radial artery provide

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19
Q

Where does a person with a fractures scaphoid typiclly show tenderness?

A

anatomic snuffbox of wrist

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20
Q

Where do most fractures of the scaphoid occur?

A

along or near scaphoid’s waist, midway b/w bone’s two poles

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21
Q

Why might fractures proximal to waist may result in delayed union or nonunion?

A

because most blood vessels enter scaphoid at and distal to its waist

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22
Q

What do fractures of proximal pole require?

A

surgery, followed by immobilization for at least 12 weeks or until evidence of radiographic union

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23
Q

What do fracture of the distal pole require?

A

do not require surgery, especially if non-displaced, and generally require only 5 to 6 weeks of immobilization

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24
Q

What are associated injuries of a fractured scaphoid?

A

Associated injuries often involve fracture and/or dislocation of lunate and fracture of trapezium and distal radius

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25
Q

What is lunatomalacia?

A

softening lunate (kienbock’s disease)

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26
Q

What causes lunatomalacia?

A
  • AVN of lunate
  • history of trauma
  • trauma linked with dislocation or with repetitive compression forces
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27
Q

What does treatment of Kienbock’s disease depend on?

A

functional limitation
pain
progression of disease

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28
Q

Mild treatment of Kienbock’s disease:

A

immobilization by casting or splinting

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29
Q

Moderate cases of Kienbock’s disease:

A

length of ulna or radius may be surgically altered as a means to reduce contact stress on lunate

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30
Q

Advanced cases of Kienbock’s disease:

A

treatments may include partial fusion of selected carpal bones, lunate excision, or proximal row carpectomy

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31
Q

What are the two primary articulations within the wrist?

A

radiocarpal and mid-carpal joints

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32
Q

How do intercarpal joints contribute to wrist motion?

A

through small gliding and rotary motions

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33
Q

What are the proximal components of the radiocarpal joint?

A

concave surfaces of radius and adjacent articular disc

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34
Q

What are the distal components of the radiocarpal joint?

A

convex proximal surfaces of scaphoid and lunate

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35
Q

Why is the triquetrum also considered part of radiocarpal joint?

A

because at full ulnar deviation, its medial surface contacts articular disc

36
Q

20% of total compression force that crosses radiocarpal joint passes through where?

A

articular disc

37
Q

80% of total compression force that crosses radiocarpal joint passes through where?

A

scaphoid and lunate to radius

38
Q

When are contact areas at radiocarpal joint greated?

A

when wrist is partially extended and ulnarly deviated

39
Q

The midcarpal joint is what?

A

articulation betwen proximal and distal row of carpal bones

40
Q

The midcarpal joint is divided into what?

A

medial and lateral joint compartments

41
Q

What is the larger medial compartment formed by?

A

convex head of capitate and apex of hamate, fitting into concave recess formed by distal surfaces of scaphoid, lunate and triquetrum

42
Q

What composes the lateral compartment of the midcarpal joint?

A

junction of slightly convex distal pole of scaphoid with slightly concave proximal surfaces of trapezium and trapezoid

43
Q

How many degrees of freedom at the wrist joint? What are they?

A

2
flexion-extension
ulnar-radial deviation

44
Q

Extension occurs with

A

radial deviation

45
Q

Flexion occurs with

A

ulnar deviation

46
Q

Resulting natural path of motion for wrist follows what path?

A

slightly oblique path

47
Q

Where is the axis of rotation for wrist movement?

A

passes through head of capitate

48
Q

For flexion and extension where is the axis? What plane of motion?

A

ML axis

sagital plane

49
Q

For radial and ulnar deviation where is the axis? What plane motion?

A

near AP

frontal plane

50
Q

What is the rotation of the wrist in the sagittal plane?

A

130°-160°

51
Q

Wrist flexion is from:

A

0° to about 70°-85°

52
Q

Wrist extension is from:

A

0° to about 60°-75°

53
Q

Total flexion normally exceeds extension by about:

A

10°-15°

54
Q

What limits end-range extension of the wrist?

A

by stiffness in thick palmar radiocarpal ligaments

55
Q

Wrist rotates in frontal plane approximately :

A

50° to 60° degrees

56
Q

Ulnar deviation:

A

0° to about 35°-40°

57
Q

Radial deviation

A

0° to about 15°-20°

58
Q

How is radial and ulnar deviation measured?

A

angle b/w radius and shaft of 3rd metacarpal

59
Q

Why is ulnar deviation normally double maximum amount of radial deviation?

A

b/c of ulnar tilt of distal radius maximum

60
Q

“Average” position of function for wrist:

A

About 10°-15° of extension and 10° of ulnar deviation

61
Q

Arthrokinematics of extension and flexion

A

convex-on-concave rotations at both radiocarpal and midcarpal joints

62
Q

During extension at radiocarpal joint:

A

convex surface of lunate rolls dorsally on radius and simultaneously slides palmarly

63
Q

During extension at midcarpal joint:

A

head of capitate rolls dorsally on lunate and simultaneously slides in palmar direction

64
Q

What is the closed-packed position of the wrist?

A

full extension

65
Q

What does full wrist extension elongate?

A

palmar radiocarpal ligaments and all muscles that cross on palmar side of wrist

66
Q

During ulnar and radial deviation at the radiocarpal joint:

A

scaphoid, lunate, and triquetrum roll ulnarly and slide significant distance radially

67
Q

At the midcarpal joint during ulnar deviation:

A

capitate rolling ulnarly and sliding slightly radially

68
Q

What helps stabilize the wrist during ulnar deviation?

A

Compression of hamate against triquetrum pushes proximal row of carpal bones against styloid process of radius

69
Q

What are two common forms of carpal instability?

A

rotational collapse of wrist: zigzag deformity

ulnar translocation of carpus

70
Q

DISI

A
  • disruption of link between scapholunate ligament causing dissaociation between scaphoid and lunate
  • lunate most often dislocated and moves dorsally
71
Q

VISI

A

injury to lunotriquetral ligament may cause lunate to dislocate volarly

72
Q

Double V System of Ligaments

A
  • Distal inverted V formed by medial and lateral legs of palmar intercarpal ligament
  • Proximal inverted V formed by lunate attachments of palmar ulnocarpal and palmar radiocarpal ligaments
73
Q

Primary Set (Act on Wrist only) wrist extensor

A

Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris

74
Q

Secondary Set (Act on Wrist and Hand) wrist extensor

A

Extensor digitorum
Extensor indicis
Extensor digiti minimi
Extensor pollicis longus

75
Q

Primary Set (Act on wrist) wrist flexor

A

Flexor carpi radialis
Flexor carpi ulnaris
Palmaris longus

76
Q

Secondary Set (act on wrist and hand) wrist flexors

A 
Flexor digitorum profundus
Flexor digitorum superficialis
Flexor pollicis longus
Abductor pollicis longus
Extensor pollicis brevis
77
Q

Radial deviators of wrist

A 
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor pollicis longus
Extensor pollicis brevis
Flexor carpi radialis
Abductor pollicis longus
Flexor pollicis longus
78
Q

Ulnar deviators of wrist

A

Extensor carpi ulnaris
Flexor carpi ulnaris
Flexor digitorum profundus and superficialis
Extensor digitorum

79
Q

Where is the transverse carpal ligament attached?

A

scaphoid and trapezium on radial side

80
Q

Abduction of CMC joint of thumb first metacarpal roll and slides on trapzium in ______ direction

A

opposite

81
Q

What is stretched in ulnar deviation?

A

lateral leg of palmar intercarpal ligament and fibers of palmar ulnocarpal ligament

82
Q

What is stretched in radial deviation?

A

medial leg of palmar intercarpal ligament and fibers of radiocarpal ligament

83
Q

Maximal grip force occurs at

A

about 30 degrees of extension

84
Q

Joint angle of peak torque of flexors

A

40 degrees of flexion

85
Q

Joint angle of peak torque of extensors

A

from 30 degrees of flexion to 70 degrees of extension

86
Q

Joint angle of peak torque of radial deviators

A

0/neutral

87
Q

Joint angle of peak torque of ulnar deviators

A

0/neutral

Biomechanics (13 decks)

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