Wrist and Hand Flashcards
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?
capitate
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.
radiocarpal:
- flexion = palmar roll of lunate onto radius, dorsal slide
- extension = dorsal roll, palmar slide
Describe the arthrokinematics of the midcarpal joint for flexion/extension.
midcarpal:
- 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.
true
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
Do the longitudinal/transverse diameters of the thumb follow the same longitudinal/transverse diameters of the SC, arthrokinematic wise?
yes: longitudinal goes in opposite ways, transverse goes in same way
Adduction and abduction of the thumb moves in what diameter?
ad/ab = longitudinal diameter, so convex on concave
Flexion and extension of the thumb occur in what diameter?
flex/extend = transverse diameter, so concave on convex
Describe the arthrokinematics in the flexion/extension of the thumb.
flex = concave metacarpal rolls ulnarly, slides ulnarly extend = rolls radially, slides radially
Do you get more motion in digit abduction when the fingers are flexed or extended?
fingers extended gives you more motion to do ad/abduction
On what axis does wrist ulnar and radial deviation occur?
about the AP axis
T/F: Extensor carpi ulnaris is better at extension than ulnar deviation.
false: ECU is best at ulnar deviation due to a longer moment arm to the ML axis
T/F: The wrist flexors have 2x the CSA of the extensors.
true
What muscle produces the greatest flexor torque of the three main wrist flexors?
FCU
What is the purpose of having pulleys in the hands?
to hold down the tendons; although these can get thick and cause pain in digits during motion
Which pulley is the most important? Why?
A1 @ MCP; it’s thicker and more fibrous, so tendon can push its way through the pulley and cause trigger finger
What is the normal range of motion at the IP joints?
70 deg flexion, 30 deg extension
What are the arthrokinematics for all MCP joints in the hand, including IP on MCP?
proximal phalange moves on metacarpal, motion is in same directions since they’re all concave on convex
Can the MCP of the thumb do ab and adduction, like the MCP of the fingers?
no, thumb just does flexion/extension
What is the position of function for the hand?
think of the splint picture: prevent contractures by keeping hand in slight extension; UD; MCP, DIP, PIP flexion; thumb abduction
What’s the difference between extrinsic and intrinsic plus positions?
1) extrinsic plus: use superficialis and profundus, and extensor digitorum, to get bear claw hand
2) intrinsic plus: use lumbricals and interossei to get lumbrical action
What muscle offsets extensor digitorum while it extends the IPs so that hyperextension at the wrist doesn’t occur?
flexor carpi radialis
For a low-level fist, what muscle is activated first?
first, profundus, then superficialis
What osteokinematics need to happen during power grip?
- flexed fingers (esp. 4 and 5)
- adducted and flexed thumb
- DAB interossei
- slight WE and UD
Compare boutonniere deformity and swan neck deformity.
boutonniere = flexed PIP, extended DIP
swan neck = extended PIP, flexed DIP
Why does ulnar drift occur?
thumb adducts and the interossei can’t resist that motion (the connective tissue they attach to is broken down), so those fingers begin to move ulnarly like the thumb
Abductor pollicis brevis is used in what grip?
precision grip, to abduct thumb
What does “power key” or “power pinch” involve?
DAB to abduct 1st digit toward thumb, adductor pollicis to bring thumb to lateral border of first digit
What causes boutonniere deformity?
central tendon on dorsum of digit tears
