Lecture 8
What is the functions of the wrist complex?
- control of length tension relationships in the hand muscles
- permit fine adjustments of grip
- loss of function in wrist cannot be replaced by compensatory movements of shoulder, elbow, forearm
- Two compound joints: radoiocarpal and mid carpal (called wrist complex)
Where is the mid carpal and radoiocarpal located on the wrist?
You can identify them by the two creases in the wrist
What do the wrist complex consist of?
- radius
- ulna
- carpals
- radioulanr disc
What are the joints of the wrist complex?
- radoiocarpal joint: favors flexion and ulnar deviation (condyloid joint 2 degree of freedom)
- mid carpal joint: favors extension and radial deviation (condyloid joint 2 degree of freedom)
- mid carpal joint: functional joint
What do ligaments provide?
provide support, application of passive forces
What is the ROM of the radoiocarpal and mid carpal joints?
- Extension is 70-75 degrees, flexion is 80-85 degrees
- extension is initiated by the distal row
- flexion is initiated by the proximal row
- radial deviation 20-25 degrees, ulnar deviation is 30-35 degrees
What are the principles of motion of the wrist complex?
- movement occurs at both proximal and distal carpal bones
- wrist flexion: initiated by there proximal row, proximal carpals slide dorsally on the distal radius and radioulnar disc
- wrist extension: initiated by the capitate in the distal carpal row,
- radial deviation: proximal carpal bones slide ulnarly
(the axis of rotation is more proximal in flexion than in extension)
- both ligaments and bones serve to check movement
In extension what way does the wrist slide?
It rolls to the same side the wrist is moving towards and slides the opposite way.
What is the dynamics of wrist extension?
- movement initiated at the distal carpal row w/ capitate at center
- convex- on concave rotations: lunate rolls dorsally on the radius and slides palmarly, head of the capitate rolls dorsally on the lunate and simultaneously slides palmarly
- the dorsal radoiocarpal ligaments become slackened and palmar radoiocarpal ligaments become taut
- 70 to 75 degrees of wrist extension
What are the dynamics of wrist flexion?
- movement initiated at proximal carpal row
- convex on concave rotations at the radoiocarpal and mid carpal joints
- lunate begins to roll palmarly on the radius while simultaneously sliding dorsally
- the head of the capitate rolls palmarly on the lunate and simultaneously slides in a dorsal direction
- palmar radoiocarpal ligaments become slackened, and the dorsal radoiocarpal ligaments become taut
- creates 80 to 85 degrees of flexion
What way does the wrist roll and slide in wrist flexion?
it rolls to the same side that the wrist flexes to and slides into the opposite direction.
What are the dynamics of ulnar deviation?
- at the radoiocarpal joint: proximal carpal bones roll ulnarly and slide radially (significant distance)
- at the mid carpal joint: capitate rolls ulnarly and slides slightly radially. Full range of ulnar deviation causes the triquetrum to contact the articular disc
- proximal row of carpals pushed against the styloid process of the radius because of the compression of the hamate against the triquetrum
- compression helps stabilize the wrist for activities requiring large gripping forces
What way does the ulnar deviation roll and slide
- it rolls toward the way of the ulnar deviation and slides the opposite way
What are the dynamics of radial deviation?
- at the mid carpal joint: captivate rolls radially and slide ulnarly
- amount of radial deviation at the radoiocarpal joint is limited bc of the radial side of the carpus impinging against the styloid process of the radius
- less stability in this position
What way does the radial deviation roll and slide?
it rolls the same direction of the radial deviation and slides in the opposite way
What does the flexor and extensor retinaculum do?
it helps prevent bow stringing when you have the tendons coming away from the joint during flexion.
- the flexor carpi ulna's muscle is the only flexor muscle outside of the retinaculum.
What are the wrist flexors?
- Flexor carpi ulanris: prime movers for wrist flexion and ulnar deviation
- Flexor carpi radialis: prime mover for wrist flexion and for radial deviation
- Palmer's longus: assists with wrist flexion
(all pass under the flexor retinaculum except palmaris longus
What are the wrist extensors?
- extensor carpi radialis longus: prime mover for wrist extension and radial deviation
- extensor carpi radialis brevis:medial position makes it most consistent extensor, most important stabilizer during forceful finger flexion, stabilizing action of long finger flexors at wrist, avoiding active insufficiency. Prime mover for radial deviation
- extensor carpi ulnaris: prime mover for wrist extension and ulnar deviation
(extensor retnaculum prevents bow stringing of long extensor tendons when hand is hyperextended at wrist joint)
What are the muscles working at the wrist?
- wrist extension: activation of radial and ulnar wrist extensors balances the wrist in extension. deviations are cancelled out
- wrist flexors: activation of radial and ulnar wrist flexors with cancellation of deviation
- radial deviation: activation of FCR and ECRL/ ECRB with cancellation of flexion and extension
- ulnar deviation: activation of FCU and ECU with cancellation of flexion and extension
What is carpal tunnel?
- purpose of carpal tunnel is to protect the structures that pass through from compression and damage (median nerve and long finer flexors)
- carpal arch: formed by both rows of carpal bones, accentuated by the hook of the hamate and anterior extension of the trapezium
What is carpal tunnel syndrome?
- a repetitive motion disorder
- results in swelling and nerve compression
- painful movement
- numbness
- weakness
LAB: drinking a glass of water
-movement: radial deviation
-contraction: concentric
-prime movers: FCR, ECRL, ECRB
LAB: Hammering a nail
- contraction: concentric
- prime movers: FCU, ECU
LAB: waving goodbye
-movement: radial deviation
- contraction: concentric
- Prime movers: FCR, ECRL, ECRB
LAB: shooting a basketball:
-movement: wrist extension
- contraction: eccentric
- prime movers: FCR, FCU