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
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
3
Q
midcarpal joint
-location
A
between proximal and distal rows of carpal bones
4
Q
bones of the distal carpal row
A
trapezium
trapezoid
capitate
hamate
5
Q
wrist osteokinematics
-motions
A
2 degrees of freedom
- sagittal plane motion (flexion/extension)
- frontal plane motion (radial and ulnar deviaiton)
6
Q
radius angulation in relation to the ulna
-what is this called
A
angulated towards the ulna by 25 degrees
called ulnar tils
7
Q
ulnar tilt
-consequence
A
allows wrist and hand to rotate further into ulnar deviation versus radial deviation
8
Q
radial deviation is limited by…
A
styloid process
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
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
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
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
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
14
Q
scaphoid convex poles
-articulate with…
A
proximal pole
-articulates with scaphoid facet of radius
distal pole
-articulates with trapezium and trapezoid
15
Q
distal carpal row
- level of mobility
- functions as a…
A
very stable
functions as a relatively immobile transverse unit
16
Q
radiocarpal joint
-type of joint
A
condyloid joint
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
18
Q
Radioulnar articular disc (TFC)
- what is it?
- function
A
biconcave fibrocartilaginous disc
transfers compressive forces from the hand to the forearm
19
Q
how is the convex head of the ulna held to the distal radioulnar joint
A
by the proximal side of the TFC
20
Q
what is the function of the distal surface of the TFC
A
holds the convex lunate and triquetrum of the RC joint
21
Q
central portion of TFC vascularity
A
avascuar
-poor healing capabilities
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
23
Q
midcarpal joint
-functional compartments
A
medial and lateral
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
25
midcarpal joint lateral compartment
- articulations
- arthrokinematic rule
convex distal pole of the scaphoid articulates with the concave trapezium and trapezoid
concave on convex rules
26
arthrokinematics during...
| -ulnar deviation
medial (ulnar) roll and lateral (radial) slide of the distal on proximal bones
27
how many bones in the hand?
| how many separate joints distal to the carpal bones?
19 bones
| 19 joints
28
each metacarpal is comprised of...
base
shaft
head
29
1st CMC
| -articulation
1st met
| trapezium
30
2nd CMC
- primary articulation
- secondary articulation
```
2nd met
primary
-trapezoid
secondary
-capatate
-trapezium
```
31
3rd CMC
| -articulation
3rd met
| capitate
32
4th CMC
- primary articulation
- secondary articulation
```
4th met
primary
-hamate
secondary
-capitate
```
33
5th CMC
| -articulation
5th met
| hamate
34
CMC joints 2-4 degrees of freedom
| -motions allowed
1 degree
| flexion/extension
35
CMC joints 1 and 5
- type of joint
- degrees of freedom
- motions allowed
```
saddle joints
2 df
flexion/extension
abduction/adduction
opposition
```
36
CMC joints
- which are stable
- which are mobile
stable
-2, 3
mobile
-1, 4, 5
37
1st CMC
- orientation compared to other CMCs
- purpose
internally rotated 90 degrees relative to other digits
allows full opposition to contact the other digits
-provides critical link for prehensile activities
38
1st CMC saddle arthrokinematics
```
trapezium
-concave in sagittal plane
-convex in frontal plane
1st metacarpal
-convex in sagittal plane
-concave in frontal plane
```
39
MCP arthrokinematics
| -type of joint
```
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
IP joints
- type of joint
- df
- arthrokinematic rule
hinge joint
1 df
concave on convex rule
41
arches of the hand
| -names
proximal transverse arch
distal transverse arch
longitudinal arch
42
longitudinal arch
- where is it rigid
- where is it mobile
- follows the shape of...
- what is considered the stable keystone of the arch
rigid proximally
mobile distally
follows shape of 2nd and 3rd rays
2nd and 3rd MCP considered stable keystone
43
proximal transverse arch
- location
- how stable
- keystone structure
at level of carpal bones
very rigid
capitate is keystone
44
distal transverse arch
- location
- how stable
- keystone structure
located at level of metacarpal heads
very mobile
MCP joints are keystone of arch
45
```
function of arches of hand
-what maintains their shape
```
allow us to grasp, hold, release, and manipulate objects of varying shapes and sizes
shape maintained by intrinsic muscles
46
primary passive structures of the hand
volar (palmar) plates
flexor tendon pulley system
extensor mechanism of the fingers
47
volar plates
- what are they
- function
```
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
damage to volar plate
- name of deformity
- description of deformity
Swan Neck Deformity
- DIP in flexion
- PIP in hyperextension
49
Swan Neck deformity etiology
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
flexor tendon pulley system
| -components
```
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
flexor tendon pulley system
| -function
maintain efficient and smooth gliding of the flexor tendons while maintaining their mechanical advantage
52
damage to flexor tendon pulley system
- names
- how it happens
```
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
extensor mechanism of fingers
| -components
extensor digitorum tendon (backbone)
- split into 3 sections
- -central (dorsal) band
- -2 lateral bands
54
extensor mechanism of fingers
- function
- how does it work
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
dorsal hood transverse fibers
- location
- why is it necessary for function of the extensor mechanism
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
dorsal oblique fibers
- contains which muscles
- location
- function
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
damage to extensor mechanism
- name of deformity
- what happens
- description of deformity
Boutonniere Deformity
tear in central slip
PIP joint in flexion
DIP in hyperextension
58
function of the wrist in relation to hand motion
controls length tension relationship in the hand
| balance and control of fine motor adjustments
59
function of the wrist for grasp and prehension
- maximum grip strength in _____
- least grip strength in _____
maximum grip strength in 20-35 extension
| minimum grip strength in full flexion
60
how much wrist motion is required for common ADL's
- which motions are most important
- what are the coupled motions
```
54 flexion
60 extension
17 radial deviation
40 ulnar deviation
extension and UD most important
combined motions
-extension with RD
-flexion with UD
```
61
wrist ligament functions
| -are palmar or dorsal ligaments stronger
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
extrinsic wrist ligaments
| -characterisitics
```
more likely to fail with injury than intrinsic
good healing (vascularity from surrounding tissue)
```
63
what are the extrinsic wrist ligaments
dorsal radiocarpal ligament
radial collateral ligament
palmar radiocarpal ligament
64
dorsal radiocarpal ligament
| -function
reinforces posterior radiocarpal joint
guides arthrokinematics of proximal row
prevents anterior dislocation of the unstable lunate
65
radial collateral ligament
| -function
provides little lateral stability
66
palmar radiocarpal ligament
- strength compared to dorsal RC ligament
- when does it provide support
```
stronger and thicker than dorsal RC lig
passive tension (even in neutral)
maximally taut in full extension
```
67
TFCC vascularity
80% avascular
68
intrinsic wrist ligaments
| -characteristics
stronger than extrinsic ligaments
lie within the synovial lining
rely on synovial fluid for nutrition
slow healing capacity (poorly vascularized)
69
intrinsic wrist ligaments
| -names
```
short ligaments
intermediate ligaments (don't need to know names)
-lunotriquetral
-scapholunate
-scaphotrapezial
long ligaments
-palmar intercarpal "V" ligament
dorsal intercarpal ligament
```
70
```
short ligaments (wrist)
-function
```
connect bones of distal row
stabilize and unite distal row
allows distal row to function as a single mechanical unit
71
palmar intercarpal "V" ligament
- function
- what do the "legs" connect
```
guides arthrokinematics
lateral leg
-palmar capitate to scaphoid
medial leg
-palmar capitate to triquetrum
```
72
dorsal intercarpal ligament
- function
- connects...
provides transverse stability
| connects trapezium, scaphoid, lunate, and triquetrum
73
retinaculum
- what are they?
- function
thickenings of fascia
can form a tunnel-like effect to keep tendons in correct position
prevents bowing out during muscle activation
74
carpal tunnel and transverse carpal ligament (TCL)
- what is it?
- function
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
thumb opposition
| -phases and description of each
phase 1
-abduction
phase 2
-flexion, medial rotation (spin) of metacarpal
76
what provides the passive tension in the MCP's to stabilize the joint for grasping
dorsal capsule
77
skier's thumb
- what is it
- in what position does it occur
UCL tear
| occurs at 45 degrees abduction, 30 degrees flexion
78
lumbricals of hand
| -function
flex MCP joint
| extend IP joint
79
interossei
| -functions
dorsal
-abduct digits and assist lumbricals
palmar
-adduct digits and assist lumbricals
80
names of functional positions of the hand
extrinsic plus
| intrinsic plus
81
extrinsic plus hand position
- what is the position
- what combined muscle activations create this position
MCP extension, PIP and DIP flexion
muscle activation
-simultaneous contraction of the extrinsic finger muscles (ED, FDS, FDP)
82
intrinsic plus hand position
- what is the position
- what combined muscle activation create this position
MCP joint flexion, PIP and DIP extension
muscle activation
-simultaneous contraction of the intrinsic finger muscles (lumbricals and interossei)
83
names of 5 types of prehension
```
power grip
precision grip
power (key) pinch
precision pinch
hook grip - laundry grip
```
84
power grip
- purpose
- shape
- muscles
```
stability, large force but low precision
spherical or cylindrical shape
muscles
-finger flexors
-intrinsic muscles
-thumb abductor/flexor
-wrist extensors to stabilize
```
85
precision grip
- purpose
- shape
- use of fingers
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
power (key) pinch
- when is it used
- where are objects held
- muscles
```
large forces needed
stabilize object between thumb and lateral border of index finger
muscles
-adductor pollicis
-1st dorsal interossei
```
87
precision pinch
- purpose
- where are objects held
fine control
objects held between thumb and index finger
tip-to-tip and pulp-to-pulp
88
hook grip - laundry grip
- what fingers involved
- shape
- muscles
does not involve thumb
partially flexed PIPs/DIPs of fingers
force primarily from FDP
89
what strucutures are responsible for the following conditions
- Boutonniere deformity
- swan neck deformity
- De Quervain's
```
Boutonniere
-extensor hood
Swan neck
-volar plate
De Quervain's
-extensor pollicis brevis
-abductor pollicis longus
```
90
most commonly
- dislocated carpal
- fractured carpal
dislocation
-lunate
fracture
-scaphoid
91
distal radius fractures
- most common MOI
- results in...
FOOSH mechanism
| results in displacement of the distal aspect of the radius
92
ulnar neuropathy
- what is damaged
- -this affects...
- result
```
deep motor branch affected
-hypothenar muscles
-medial 2 lumbricals
-palmar interossei
-dorsal interossei
-adductor pollicis
results in atrophy
```
