Chapter 8 - The Hand Flashcards
make-up of the hand
19 bones
29 muscles
- takes up a large part of the motor/sensory cortex of brain
palmar creases
- distal and middle digital creases
- proximal digital crease
- proximal and distal palmar creases
concavity of the palm
supported by three integrated arch systems:
1) longitudinal arch(follows 3rd phalanx)
2) distal transverse arch(knuckles or MCP joints)
3) proximal transverse arch(CMC joints)
Which metacarpals are the most mobile?
1st, 4th, and 5th
Thumb CMC
- classic saddle joint
- Trapezium/1st metacarpal
- trapezium = concave (palmar to dorsal)
- trapezium = convex (medial to lateral)
- 2 degrees of freedom(flex/ext & abd/add)
- opposition = combination of all
ROM of thumb CMC
abduction = 50 degrees Flexion = 45-50
abduction of the thumb
convex-on-concave
- caused by abductor pollicis longus
- roll anterior/slide posterior
flexion of thumb
concave-on-convex
- roll medially/slide medially
- stretches medial collateral ligament
extension of the thumb
concave-on-convex
- roll laterally/slide laterally
- stretches the anterior oblique ligament
opposition
2 phases:
1) abduction
2) flexion with medial rotation
- posterior oblique ligament is taut
- muscle = opponens pollicis
CMC joints of fingers
2nd and 3rd are more rigid for stability
- 4th and 5th are mobile
- intermetacarpal joints at bases of 2nd through 5th
ROM CMC joints
- 2nd and 3rd relatively stable
- 4th flexes = 10 degrees(hamate bone)
- 5th flexes = 20-25 degrees(hamate bone)
MCP of fingers
2 degrees of motion = flex/ext & abd/add
- rotation as an accessory motion
- convex head of MC’s to concave proximal phalanges
- close packed position = 70 degrees of flexion
- collateral ligaments are tightest and most stable
limiting extension of MCP
prevented by palmar plates
- MCP can be hyper extended(unlike IP joints)
ROM of MCP
increases from 2nd digit to 5th digit
- flexion = 90 - 115
- passive hypertension = 30-45
abduction and adduction of fingers during flexion
limited because radial and ulnar collateral ligaments are stretched
- dorsal capsule is also stretched
abduction of fingers
concave on convex
- roll and slide in same direction
- muscles = dorsal interossei
- ulnar collateral ligament
- axis through head of MC
flexion of MCP joint
head of the MC is cam-shaped
- flexion increases the distance between attachment points of the collateral ligaments
- in contrast to PIP where distance remains constant
thumb MCP
1 degree of freedom(flex/ext)
- flexion = 60 degrees
- concave-on-convex(roll and slide same direction)
- limited hyperextension
- muscle = flexor pollicis brevis, some flexor pollicis longus
- dorsal capsule being stretched during flexion
finger IP joints
1 degree of freedom(flexion/extension)
- tongue in groove articulation
- closed packed near full extension
- PIP flex = 100-129
- DIP flex = 70-90
- palmar plate limits extension
- collateral ligament stretched during flexion
Thumb IP joint
1 degree of freedom(flex/ext)
- similar to fingers
- flex = 70 degrees
- passive hyperextension to 20 degrees
“position of function”
wrist = 20-30 degrees of extension with slight ulnar deviation
fingers = 35-45 degrees of MCP flex
- 15-30 degrees of PIP and DIP flexion
thumb = 35-45 degrees of CMC joint abduction
intrinsic hand muscles
interossei, lumbricals, adductor pollicis, opponens pollicis
extrinsic hand muscles
muscles that cross wrist joint
flexor digitorum superficialis
medial epicondyle to middle phalanx
- median nerve
flexor digitorum profundus
to distal phalanx
- median and ulnar nerve
lumbricals
attach on the tendon of flexor digitorum profundus
- flexion of MCP and extension of IP’s
- insert on the dorsal hood
- 1&2 = median nerve
- 3&4 = ulnar nerve
through the carpal tunnel
through the tunnel: - flexor digitorum superficialis and profundus - flexor pollicis longus - flexor carpi radialis - median nerve - ulnar(flexor digitorums) and radial(flexor pollicis longus) synovial sheath outside of tunnel: - ulnar nerve
make up of carpal tunnel
top = transverse carpal ligament bottom = pisiform, triquetrum, lunate, scaphoid
during PIP flexion
flexor digitorum superficialis flexes
- extensor digitorum and extensor carpi radialis brevis isometrically contract to prevent wrist flexion and MCP flexion
tendodesis action
as the wrist is extended, thumb and fingers automatically flex because of stretch placed on the extrinsic digital flexors(passively)
finger abduction
dorsal interossei and abductor digiti minimi
finger adduction
palmar interossei
- also thumb flexion
intrinsic-plus position
MCP’s flexed
DIP’s and PIP’s extended
- lumbricals and interossei
extrinsic-plus position
MCP’s extended
DIP’s and PIP’s flexed
“claw” position
ulnar nerve lesion(3&4 lumbricals paralyzed)
- 4&5 MCP’s hyperextended
- DIP’s and PIP’s partially flexed
- manually holding MCP’s in flexion, extensor digitorum extends DIP and PIP joints
active finger extension progression
1) intrinsic muscles activate(lumbricals and interossei)
2) PIP joints extend
3) oblique retinacular ligament is stretched
4) DIP joint extends
Finger flexion progression
Early Phase:
- flexor digitorum profundus and superficialis, and interosseus muscles flex joints of finger
Late Phase:
- flexing continues, extensor carpi radialis brevis extends wrist slightly, extensor digitorum decelerates flexion of MCP joint
finger extension progression
Early phase:
- extensor digitorum extends MCP joint
Middle phase:
- intrinsic muscles(lumbricals and interossei) assist in extension of PIP and DIP
- also they produce flexion at MCP to prevent hyperextension
Late phase:
- muscle activation continues
- flexor carpi radialis slightly flexes wrist
zigzag deformity of the thumb
radially directed dislocation of CMC joint
- hyperextension of MCP joint(from extensor pollicis longus)
- IP joints remain partially flexed(flexor pollicis longus)
- caused by rheumatoid arthritis
palmar dislocation of the MCP joint
palmar directed bowstring force of flexor tendons(FDP & FDS) against the palmar plate
- rupture of the weakened collateral ligaments
- caused by rheumatoid arthritis
ulnar drift MCP joint
ruptured radial collateral ligament
- extensor digitorum pulls in ulnar direction at MCP joint
Swan-neck deformity
1) hyperextension of PIP
- palmar plate damaged(over stretch)
2) flexion of DIP
- flexor digitorum profundus
Boutonniere deformity
1) flexion of PIP
- ruptured central band
- slipped lateral band
2) hyperextension of DIP
