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S1 Biomechanics > Biomechanics Wrist and Hand > Flashcards

Biomechanics Wrist and Hand Flashcards

1
Q

joints of the wrist

-purpose of the wrist

A

radiocarpal joint
midcarpal joint
assists the hands as they move in space

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2
Q

radiocarpal joint

-components

A 
distal radius
radioulnar articulate disc
proximal row of carpal bones
-scaphoid
-lunate
-triquetrum
-I do not believe the pisiform articulates with the radius
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3
Q

midcarpal joint

-location

A

between proximal and distal rows of carpal bones

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4
Q

bones of the distal carpal row

A

trapezium
trapezoid
capitate
hamate

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5
Q

wrist osteokinematics

-motions

A

2 degrees of freedom

  • sagittal plane motion (flexion/extension)
  • frontal plane motion (radial and ulnar deviaiton)
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6
Q

radius angulation in relation to the ulna

-what is this called

A

angulated towards the ulna by 25 degrees

called ulnar tils

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7
Q

ulnar tilt

-consequence

A

allows wrist and hand to rotate further into ulnar deviation versus radial deviation

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8
Q

radial deviation is limited by…

A

styloid process

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9
Q

palmar tilt

  • caused by…
  • allows for…
A

distal articular surface of radius is angulated 10 degrees in the palmar direction
allows for greater wrist flexion than extension

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10
Q

scaphoid

-which row is it in, anatomically and functionally

A

spans both proximal and distal row, both anatomically and functionally, due to its elongated shape

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11
Q

pisiform

  • type of bone
  • location
  • function
A

sesamoid bone that sits on top of the triquetrum

mechanically enhances the pull of the flexor carpi ulnaris by giving it a longer moment arm

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12
Q

promixal carpal row

  • which muscles attach to these
  • mobility compared to distal row
  • overall function
A

no muscles attach there
very mobile compared to distal row
servse as a mechanical link between the forearm and hand

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13
Q

when the link created by the proximal carpal row is compromised…

A

you have a zigzag collapse
ligaments are typically damaged
result is carpal instability

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14
Q

scaphoid convex poles

-articulate with…

A

proximal pole
-articulates with scaphoid facet of radius
distal pole
-articulates with trapezium and trapezoid

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15
Q

distal carpal row

  • level of mobility
  • functions as a…
A

very stable

functions as a relatively immobile transverse unit

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16
Q

radiocarpal joint

-type of joint

A

condyloid joint

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17
Q

how does load sharing occur between the radius and ulna

-why is it important

A

ulna has no articulation with carpals

load transmitted to ulna via interosseus membrane

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18
Q

Radioulnar articular disc (TFC)

  • what is it?
  • function
A

biconcave fibrocartilaginous disc

transfers compressive forces from the hand to the forearm

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19
Q

how is the convex head of the ulna held to the distal radioulnar joint

A

by the proximal side of the TFC

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20
Q

what is the function of the distal surface of the TFC

A

holds the convex lunate and triquetrum of the RC joint

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21
Q

central portion of TFC vascularity

A

avascuar

-poor healing capabilities

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22
Q

TFCC function

A

primary stabilizer of distal radioulnar joint
reinforces ulnar side of wrist
forms concavity in RC joint
transfers force from hand to forearm
binds ulna and radius together distally while allowing radius to rotate over fixed ulna for pronation and supination

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23
Q

midcarpal joint

-functional compartments

A

medial and lateral

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24
Q

midcarpal joint medial compartment

  • articulations
  • arthrokinematic rule
A

articulations
-convex head of capitate and apex of hamate articulate with the concave depression in the scaphoid, lunate, and triquetrum
follows convex on concave rule

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25
Q

midcarpal joint lateral compartment

  • articulations
  • arthrokinematic rule
A

convex distal pole of the scaphoid articulates with the concave trapezium and trapezoid
concave on convex rules

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26
Q

arthrokinematics during…

-ulnar deviation

A

medial (ulnar) roll and lateral (radial) slide of the distal on proximal bones

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27
Q

how many bones in the hand?

how many separate joints distal to the carpal bones?

A

19 bones

19 joints

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28
Q

each metacarpal is comprised of…

A

base
shaft
head

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29
Q

1st CMC

-articulation

A

1st met

trapezium

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30
Q

2nd CMC

  • primary articulation
  • secondary articulation
A 
2nd met
primary
-trapezoid
secondary
-capatate
-trapezium
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31
Q

3rd CMC

-articulation

A

3rd met

capitate

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32
Q

4th CMC

  • primary articulation
  • secondary articulation
A 
4th met
primary
-hamate
secondary
-capitate
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33
Q

5th CMC

-articulation

A

5th met

hamate

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34
Q

CMC joints 2-4 degrees of freedom

-motions allowed

A

1 degree

flexion/extension

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35
Q

CMC joints 1 and 5

  • type of joint
  • degrees of freedom
  • motions allowed
A 
saddle joints
2 df
flexion/extension
abduction/adduction
opposition
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36
Q

CMC joints

  • which are stable
  • which are mobile
A

stable
-2, 3
mobile
-1, 4, 5

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37
Q

1st CMC

  • orientation compared to other CMCs
  • purpose
A

internally rotated 90 degrees relative to other digits
allows full opposition to contact the other digits
-provides critical link for prehensile activities

38
Q

1st CMC saddle arthrokinematics

A 
trapezium
-concave in sagittal plane
-convex in frontal plane
1st metacarpal
-convex in sagittal plane
-concave in frontal plane
39
Q

MCP arthrokinematics

-type of joint

A 
distal end of met has convex head articulating with concave base of proximal phalanx
condyloid joint
-2 df
MCP of thumb has 1df
all MCP joints follow concave on convex
40
Q

IP joints

  • type of joint
  • df
  • arthrokinematic rule
A

hinge joint
1 df
concave on convex rule

41
Q

arches of the hand

-names

A

proximal transverse arch
distal transverse arch
longitudinal arch

42
Q

longitudinal arch

  • where is it rigid
  • where is it mobile
  • follows the shape of…
  • what is considered the stable keystone of the arch
A

rigid proximally
mobile distally
follows shape of 2nd and 3rd rays
2nd and 3rd MCP considered stable keystone

43
Q

proximal transverse arch

  • location
  • how stable
  • keystone structure
A

at level of carpal bones
very rigid
capitate is keystone

44
Q

distal transverse arch

  • location
  • how stable
  • keystone structure
A

located at level of metacarpal heads
very mobile
MCP joints are keystone of arch

45
Q 
function of arches of hand
-what maintains their shape
A

allow us to grasp, hold, release, and manipulate objects of varying shapes and sizes
shape maintained by intrinsic muscles

46
Q

primary passive structures of the hand

A

volar (palmar) plates
flexor tendon pulley system
extensor mechanism of the fingers

47
Q

volar plates

  • what are they
  • function
A 
what
-fibrocartilage plates located on the volar surface of MCP, PIP, and DIP joints
function
-reinforce anterior joint capsules
-prevent impingement of flexor tendons during flexion
-limit hyperextension at these joints
48
Q

damage to volar plate

  • name of deformity
  • description of deformity
A

Swan Neck Deformity

  • DIP in flexion
  • PIP in hyperextension
49
Q

Swan Neck deformity etiology

A

can be caused by synovitis of the flexor tendon sheath
increased flexion pull on the MP joint causes an imbalance to the extensor central slip through the long extensor tendons and the intrinsic muscles
stretch to the volar plate at the PIP causes hyperextension of the PIP
lateral intrinsic tendons shift dorsally and reciprocal flexion occurs at the DIP

50
Q

flexor tendon pulley system

-components

A 
2 digital flexor tendons
-FDS
-FDP
-tendons lie in their synovial sheaths which are secured against the phalanges by a fibrous sheath
5 annular pulleys (A1-A5)
3 cruciform pulleys (C1-C3)
51
Q

flexor tendon pulley system

-function

A

maintain efficient and smooth gliding of the flexor tendons while maintaining their mechanical advantage

52
Q

damage to flexor tendon pulley system

  • names
  • how it happens
A 
bowstring phenomenon
-rupture a pulley (A1-5)
trigger finger
-nodule of tendon becomes inflamed
-nodule gets trapped behind tendon sheath, finger becomes stuck in flexed position
53
Q

extensor mechanism of fingers

-components

A

extensor digitorum tendon (backbone)

  • split into 3 sections
  • -central (dorsal) band
  • -2 lateral bands
54
Q

extensor mechanism of fingers

  • function
  • how does it work
A

coordinates movements between PIP and DIP joints
mechanism has multiple attachments along the phalanges allowing transfer of extensor forces distally through the entire digit

55
Q

dorsal hood transverse fibers

  • location
  • why is it necessary for function of the extensor mechanism
A

at proximal end of extensor mechanism at the MCP joints
transverse fibers run perpendicular to the ED tendon, attaching to the volar plate of the proximal phalanx to create a sling that assists the ED tendon with MCP extension

56
Q

dorsal oblique fibers

  • contains which muscles
  • location
  • function
A

contains muscle fibers of the lumbricals and interossei
runs distally to attach into lateral band of extensor mechanism
aids extensor mechanism in extension of PIP and DIP joints

57
Q

damage to extensor mechanism

  • name of deformity
  • what happens
  • description of deformity
A

Boutonniere Deformity
tear in central slip
PIP joint in flexion
DIP in hyperextension

58
Q

function of the wrist in relation to hand motion

A

controls length tension relationship in the hand

balance and control of fine motor adjustments

59
Q

function of the wrist for grasp and prehension

  • maximum grip strength in _____
  • least grip strength in _____
A

maximum grip strength in 20-35 extension

minimum grip strength in full flexion

60
Q

how much wrist motion is required for common ADL’s

  • which motions are most important
  • what are the coupled motions
A 
54 flexion
60 extension
17 radial deviation
40 ulnar deviation
extension and UD most important
combined motions
-extension with RD
-flexion with UD
61
Q

wrist ligament functions

-are palmar or dorsal ligaments stronger

A

restrict joint motion and oppose joint surfaces
can cause bone movement (displacement)
maintain structure
facilitate precise loads
transmit loads to proximal and distal segments
palmar ligaments stronger

62
Q

extrinsic wrist ligaments

-characterisitics

A 
more likely to fail with injury than intrinsic
good healing (vascularity from surrounding tissue)
63
Q

what are the extrinsic wrist ligaments

A

dorsal radiocarpal ligament
radial collateral ligament
palmar radiocarpal ligament

64
Q

dorsal radiocarpal ligament

-function

A

reinforces posterior radiocarpal joint
guides arthrokinematics of proximal row
prevents anterior dislocation of the unstable lunate

65
Q

radial collateral ligament

-function

A

provides little lateral stability

66
Q

palmar radiocarpal ligament

  • strength compared to dorsal RC ligament
  • when does it provide support
A 
stronger and thicker than dorsal RC lig
passive tension (even in neutral)
maximally taut in full extension
67
Q

TFCC vascularity

A

80% avascular

68
Q

intrinsic wrist ligaments

-characteristics

A

stronger than extrinsic ligaments
lie within the synovial lining
rely on synovial fluid for nutrition
slow healing capacity (poorly vascularized)

69
Q

intrinsic wrist ligaments

-names

A 
short ligaments
intermediate ligaments (don't need to know names)
-lunotriquetral
-scapholunate
-scaphotrapezial
long ligaments
-palmar intercarpal "V" ligament
dorsal intercarpal ligament
70
Q 
short ligaments (wrist)
-function
A

connect bones of distal row
stabilize and unite distal row
allows distal row to function as a single mechanical unit

71
Q

palmar intercarpal “V” ligament

  • function
  • what do the “legs” connect
A 
guides arthrokinematics
lateral leg
-palmar capitate to scaphoid
medial leg
-palmar capitate to triquetrum
72
Q

dorsal intercarpal ligament

  • function
  • connects…
A

provides transverse stability

connects trapezium, scaphoid, lunate, and triquetrum

73
Q

retinaculum

  • what are they?
  • function
A

thickenings of fascia
can form a tunnel-like effect to keep tendons in correct position
prevents bowing out during muscle activation

74
Q

carpal tunnel and transverse carpal ligament (TCL)

  • what is it?
  • function
A

TCL makes a tunnel with carpal bones (carpal tunnel)
passageway for median nerve and 9 extrinsic flexor muscles of the digits
restrains ligaments from bowstringing

75
Q

thumb opposition

-phases and description of each

A

phase 1
-abduction
phase 2
-flexion, medial rotation (spin) of metacarpal

76
Q

what provides the passive tension in the MCP’s to stabilize the joint for grasping

A

dorsal capsule

77
Q

skier’s thumb

  • what is it
  • in what position does it occur
A

UCL tear

occurs at 45 degrees abduction, 30 degrees flexion

78
Q

lumbricals of hand

-function

A

flex MCP joint

extend IP joint

79
Q

interossei

-functions

A

dorsal
-abduct digits and assist lumbricals
palmar
-adduct digits and assist lumbricals

80
Q

names of functional positions of the hand

A

extrinsic plus

intrinsic plus

81
Q

extrinsic plus hand position

  • what is the position
  • what combined muscle activations create this position
A

MCP extension, PIP and DIP flexion
muscle activation
-simultaneous contraction of the extrinsic finger muscles (ED, FDS, FDP)

82
Q

intrinsic plus hand position

  • what is the position
  • what combined muscle activation create this position
A

MCP joint flexion, PIP and DIP extension
muscle activation
-simultaneous contraction of the intrinsic finger muscles (lumbricals and interossei)

83
Q

names of 5 types of prehension

A 
power grip
precision grip
power (key) pinch
precision pinch
hook grip - laundry grip
84
Q

power grip

  • purpose
  • shape
  • muscles
A 
stability, large force but low precision
spherical or cylindrical shape
muscles
-finger flexors
-intrinsic muscles
-thumb abductor/flexor
-wrist extensors to stabilize
85
Q

precision grip

  • purpose
  • shape
  • use of fingers
A

control, precision
fingers partially flexed, thumb partially abducted
selectively use fingers and/or thumb to improve security and modify force
alter distal transverse arch to fit objects

86
Q

power (key) pinch

  • when is it used
  • where are objects held
  • muscles
A 
large forces needed
stabilize object between thumb and lateral border of index finger
muscles
-adductor pollicis
-1st dorsal interossei
87
Q

precision pinch

  • purpose
  • where are objects held
A

fine control
objects held between thumb and index finger
tip-to-tip and pulp-to-pulp

88
Q

hook grip - laundry grip

  • what fingers involved
  • shape
  • muscles
A

does not involve thumb
partially flexed PIPs/DIPs of fingers
force primarily from FDP

89
Q

what strucutures are responsible for the following conditions

  • Boutonniere deformity
  • swan neck deformity
  • De Quervain’s
A 
Boutonniere
-extensor hood
Swan neck
-volar plate
De Quervain's
-extensor pollicis brevis
-abductor pollicis longus
90
Q

most commonly

  • dislocated carpal
  • fractured carpal
A

dislocation
-lunate
fracture
-scaphoid

91
Q

distal radius fractures

  • most common MOI
  • results in…
A

FOOSH mechanism

results in displacement of the distal aspect of the radius

92
Q

ulnar neuropathy

  • what is damaged
  • -this affects…
  • result
A 
deep motor branch affected
-hypothenar muscles
-medial 2 lumbricals
-palmar interossei
-dorsal interossei
-adductor pollicis
results in atrophy

S1 Biomechanics (12 decks)

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