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Flashcards in Wrist and Hand Deck (54)
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Why is there more flexion in the wrist (85 deg) than extension (25 deg)?

because of the palmar tilt (10 deg posterior) at the end of the radius
- the carpal bones run into the radius quicker when they do extension vs. flexion


Through what bone is the axis of rotation for the wrist?



What are the top three fractured carpal bones?

1) scaphoid
2) lunate (1st most dislocated)
3) triquetrum


Name the bones in order, looking from your palmar side and listing the bottom row then top row, radius to ulna.

bottom row: scaphoid, lunate, triquetrum, pisiform
top row: trapezium, trapezoid, capitate, hamate


What's the most moveable carpal bone?

lunate, making it the most dislocated bone


Which side of the carpal bones is more moveable, medial or lateral?

medial is more moveable


The motions at the wrist include what two joints?

1) radiocarpal (lunate moving on radius)
2) midcarpal (capitate moving on lunate)


The radiocarpal joint has what basic arthrokinetic rule?

convex on concave


What gives stability to the wrist?

collateral ligaments and intercarpal ligaments


What carpal bone does Kienbock's disease involve? What happens? How will the patient present?

- kienbock's disease = avascular necrosis of the lunate, due to trauma or compression of bone
- patient presents with swelling, pain, and decreased ROM


Where do most wrist fractures occur from breaking a fall?

at the waist of the scaphoid bone, since the styloid process of the radius runs right up into it


How many degrees of ulnar and radial deviation can we get?

ulnar = 40 deg
radial = 20 deg


What allows us to get more ulnar deviation than radial?

- b/c the radius directly articulates w/ carpal bones and the ulna doesn't
- due to ulnar tilt of radius


What are the degrees needed of ulnar/radial deviation to complete almost all ADLs?

30 degrees for ulnar deviation, 10 radial deviation


How much flexion/extension do you need at the wrist to complete most ADLs?

40 degrees either way


Describe the arthrokinematics of the radiocarpal joint for flexion/extension.

- flexion = palmar roll of lunate onto radius, dorsal slide
- extension = dorsal roll, palmar slide


Describe the arthrokinematics of the midcarpal joint for flexion/extension.

- flexion = palmar roll of capitate on lunate, dorsal slide
- extension = dorsal roll, palmar slide


In flexion and extension, from which joint (midcarpal or radiocarpal) does most motion come from?

- split 50/50 for flex and extend
* for ulnar and radial deviation though, it's 60% MIDCARPAL


Describe the arthrokinetmatics of ulnar deviation.

1) lunate rolls ulnarly on radius, slides radially
2) capitate rolls ulnarly, slides radially


At what position do we have the most grip strength?

30-35 degrees of wrist extension, 5 degrees ulnar deviation


What happens to the lunate in volar intercalated segment instability (VISI)?

lunate displaced palmarly, angle to scaphoid is less than 30 (zig-zag deformity)


T/F: The longer moment arm a muscle has, perpendicular to the axis of the muscle it's acting on, the better it's able to act on that muscle.



T/F: The wrist extensors are stronger than the wrist flexors.

false, wrist flexors are stronger due to more CSA


When the lunate creates an angle with the scaphoid that is greater than 60 deg, what kind of carpal instability has occurred?

dorsal intercalated segment instability (DISI)


T/F: During wrist flexion, you have passive insufficiency of the wrist extensors.

true; too stretched to give full ROM


T/F: During wrist flexion, you have active insufficiency of the wrist flexors.

true; too shortened to produce full flexion force


What two muscles synergistically flex the wrist, allowing straight wrist flexion with no deviation?

flexor carpi ulnaris and radialis


T/F: You have more ulnar deviators than radial deviators.

false, more radial: they do 15% greater isometric torque than ulnar deviators


Which digits are more rigid?

2-3 are rigid, 4-5 give a lot of movement (as well as the thumb)


What bones are moving on each other at the thumb joint?

metacarpal moves on the trapezium in the saddle joint