Biomechanics > Wrist > Flashcards

Wrist Flashcards

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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
What is lunatomalacia?
softening lunate (kienbock's disease)
26
What causes lunatomalacia?
- AVN of lunate - history of trauma - trauma linked with dislocation or with repetitive compression forces
27
What does treatment of Kienbock's disease depend on?
functional limitation pain progression of disease
28
Mild treatment of Kienbock's disease:
immobilization by casting or splinting
29
Moderate cases of Kienbock's disease:
length of ulna or radius may be surgically altered as a means to reduce contact stress on lunate
30
Advanced cases of Kienbock's disease:
treatments may include partial fusion of selected carpal bones, lunate excision, or proximal row carpectomy
31
What are the two primary articulations within the wrist?
radiocarpal and mid-carpal joints
32
How do intercarpal joints contribute to wrist motion?
through small gliding and rotary motions
33
What are the proximal components of the radiocarpal joint?
concave surfaces of radius and adjacent articular disc
34
What are the distal components of the radiocarpal joint?
convex proximal surfaces of scaphoid and lunate
35
Why is the triquetrum also considered part of radiocarpal joint?
because at full ulnar deviation, its medial surface contacts articular disc
36
20% of total compression force that crosses radiocarpal joint passes through where?
articular disc
37
80% of total compression force that crosses radiocarpal joint passes through where?
scaphoid and lunate to radius
38
When are contact areas at radiocarpal joint greated?
when wrist is partially extended and ulnarly deviated
39
The midcarpal joint is what?
articulation betwen proximal and distal row of carpal bones
40
The midcarpal joint is divided into what?
medial and lateral joint compartments
41
What is the larger medial compartment formed by?
convex head of capitate and apex of hamate, fitting into concave recess formed by distal surfaces of scaphoid, lunate and triquetrum
42
What composes the lateral compartment of the midcarpal joint?
junction of slightly convex distal pole of scaphoid with slightly concave proximal surfaces of trapezium and trapezoid
43
How many degrees of freedom at the wrist joint? What are they?
2 flexion-extension ulnar-radial deviation
44
Extension occurs with
radial deviation
45
Flexion occurs with
ulnar deviation
46
Resulting natural path of motion for wrist follows what path?
slightly oblique path
47
Where is the axis of rotation for wrist movement?
passes through head of capitate
48
For flexion and extension where is the axis? What plane of motion?
ML axis | sagital plane
49
For radial and ulnar deviation where is the axis? What plane motion?
near AP | frontal plane
50
What is the rotation of the wrist in the sagittal plane?
130°-160°
51
Wrist flexion is from:
0° to about 70°-85°
52
Wrist extension is from:
0° to about 60°-75°
53
Total flexion normally exceeds extension by about:
10°-15°
54
What limits end-range extension of the wrist?
by stiffness in thick palmar radiocarpal ligaments
55
Wrist rotates in frontal plane approximately :
50° to 60° degrees
56
Ulnar deviation:
0° to about 35°-40°
57
Radial deviation
0° to about 15°-20°
58
How is radial and ulnar deviation measured?
angle b/w radius and shaft of 3rd metacarpal
59
Why is ulnar deviation normally double maximum amount of radial deviation?
b/c of ulnar tilt of distal radius maximum
60
“Average” position of function for wrist:
About 10°-15° of extension and 10° of ulnar deviation
61
Arthrokinematics of extension and flexion
convex-on-concave rotations at both radiocarpal and midcarpal joints
62
During extension at radiocarpal joint:
convex surface of lunate rolls dorsally on radius and simultaneously slides palmarly
63
During extension at midcarpal joint:
head of capitate rolls dorsally on lunate and simultaneously slides in palmar direction
64
What is the closed-packed position of the wrist?
full extension
65
What does full wrist extension elongate?
palmar radiocarpal ligaments and all muscles that cross on palmar side of wrist
66
During ulnar and radial deviation at the radiocarpal joint:
scaphoid, lunate, and triquetrum roll ulnarly and slide significant distance radially
67
At the midcarpal joint during ulnar deviation:
capitate rolling ulnarly and sliding slightly radially
68
What helps stabilize the wrist during ulnar deviation?
Compression of hamate against triquetrum pushes proximal row of carpal bones against styloid process of radius
69
What are two common forms of carpal instability?
rotational collapse of wrist: zigzag deformity | ulnar translocation of carpus
70
DISI
- disruption of link between scapholunate ligament causing dissaociation between scaphoid and lunate - lunate most often dislocated and moves dorsally
71
VISI
injury to lunotriquetral ligament may cause lunate to dislocate volarly
72
Double V System of Ligaments
- 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
Primary Set (Act on Wrist only) wrist extensor
Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris
74
Secondary Set (Act on Wrist and Hand) wrist extensor
Extensor digitorum Extensor indicis Extensor digiti minimi Extensor pollicis longus
75
Primary Set (Act on wrist) wrist flexor
Flexor carpi radialis Flexor carpi ulnaris Palmaris longus
76
Secondary Set (act on wrist and hand) wrist flexors
``` Flexor digitorum profundus Flexor digitorum superficialis Flexor pollicis longus Abductor pollicis longus Extensor pollicis brevis ```
77
Radial deviators of wrist
``` Extensor carpi radialis longus Extensor carpi radialis brevis Extensor pollicis longus Extensor pollicis brevis Flexor carpi radialis Abductor pollicis longus Flexor pollicis longus ```
78
Ulnar deviators of wrist
Extensor carpi ulnaris Flexor carpi ulnaris Flexor digitorum profundus and superficialis Extensor digitorum
79
Where is the transverse carpal ligament attached?
scaphoid and trapezium on radial side
80
Abduction of CMC joint of thumb first metacarpal roll and slides on trapzium in ______ direction
opposite
81
What is stretched in ulnar deviation?
lateral leg of palmar intercarpal ligament and fibers of palmar ulnocarpal ligament
82
What is stretched in radial deviation?
medial leg of palmar intercarpal ligament and fibers of radiocarpal ligament
83
Maximal grip force occurs at
about 30 degrees of extension
84
Joint angle of peak torque of flexors
40 degrees of flexion
85
Joint angle of peak torque of extensors
from 30 degrees of flexion to 70 degrees of extension
86
Joint angle of peak torque of radial deviators
0/neutral
87
Joint angle of peak torque of ulnar deviators
0/neutral
Biomechanics
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