biomechanics of wrist

Question 1

wrist function

Answer 1

controls length tension relationship

fine movements for grip

load transfer from hand to from forearm

Question 2

hand function

Answer 2

sensory and motor

essential for prehension and fine motor control

thumb opposition

rich supply of sensory receptors

Question 3

wrist joint type

Answer 3

biaxial
condyloid joint

flexion extension
ulnar radial deviations

2 dof
capsular- equal f and e

Question 4

normal wrist rom

Answer 4

flex 65-85
ext 60-80
RD 15-21
UD 20-45

Question 5

functional wrist position

Answer 5

20-35 ext
10-15 UD

Question 6

close pack wrist

Answer 6

full extension

Question 7

radiocarpal joint

Answer 7

radius, TFCC, triquetrum, lunate, scaphoid

axial loading sharing- scaphoid/lunate 80%; TFCC 20%

radial styloid typically more distal than ulnar

Question 8

if ulnar styloid more proximal

Answer 8

• ulnar variance
  associated with Keinbocks

Question 9

if ulnar styloid more distal

Answer 9

+ ulnar variance
associated with TFCC impingment

Question 10

proximal row of carpal bones

Answer 10

highly mobile
location of most carpal instabilities
susceptible to collapse with load

Question 11

intrinsic ligaments for proximal row of carpal bones

Answer 11

scapulolunate interosseous

lunotriquetral interosseous

Question 12

what one muscle attaches to proximal carpal bones

Answer 12

FCU

Question 13

scaphoid

Answer 13

key participant for wrist action
supports weight of arm (CKC)

transmits forces from hand to forearm
moves with either proximal or distal row of carpals

exerts flexion moment on proximal row

most commonly fractured in FOOSH

Question 14

lunate

Answer 14

most commonly dislocated carpal bone

exerts extension moment on proximal row

Question 15

midcarpal joint and distal row of carpals

Answer 15

functional not anatomical joint

distal carpals move as fixed unit

functional union of distal carpals and metacarpals are foundation of transverse and longitudinal arches of the hand

Question 16

wrist ligaments

Answer 16

thinner dorsally

thicker and stronger volarly

extrinsic and intrinsic

Question 17

extrinsic wrist ligaments

Answer 17

connect radius/ulna to carpals
connect carpals to metacarpals

Question 18

intrinsic wrist ligaments

Answer 18

stronger
carpal to carpal
slow healing - lie within synovial lining

Question 19

dorsal intercalated segment

Answer 19

carpal instability

named for distal lunate
scapholunate disruption
lunate tips dorsally due to connection to triquetrum

Question 20

volar intercalated segment

Answer 20

named for distal lunate

lunotriquetral disruption

lunate dips palmarly due to connection to scaphoid

Question 21

wrist extension arthro

Answer 21

lunate rolls dorsally/ slides volarly on distal radius

capitate rolls dorsally/ slides volarly on lunate

closed packed position

Question 22

ulnar deviation arthro

Answer 22

proximal row rolls ulnarly, slides radially

axis through head of capitate

Question 23

radial deviation arthro

Answer 23

proximal row rolls radially, slides ulnarly

axis through head of capitate

Question 24

wrist muscles stabilized by

Answer 24

extensor retinaculum and transverse carpal ligament

Question 25

primary role of wrist muscles

Answer 25

stable base for the hand
optimize length tension relationship in long fingers

Question 26

work capacity for wrist muscles

Answer 26

flexors 2x > extensors

RD> UD