biomechanics elbow, forearm, wrist Flashcards
Flexion/extension, shorten/lengthen, upper extremity
humero ulnar joint
humero radial joint
rotation- pronate/supination
proximal radioulnar joint
distal radioulnar joint
functional range of motion of the elbow
30 to 130°
capsular pattern for the elbow
Flexion greater than extension
bony stability of the humeroulnar joint
interlocking of trochlea groove of humorous into ulnar trochlear
coronoid process into coronoid fossa
olecranon into olecranon fossa
Coronoid process prevents
Posterior displacement with flexion
olecranon prevents
Hyper extension
elbow capsule
humeral ulnar, humero radial, proximal radioulnar joints
anterior and posterior are weak
Laterally reinforced with ligaments
Max volume is 70 to 80° of flexion
Medial collateral ligament
anterior- 1° of valgus restraint through all elbow motion
Posterior - taught in full flexion
Transverse -no role in stability
Lateral collateral ligament complex
lateral collateral ligament
Lateral ulnar collateral ligament
Annular ligament
lateral (radial) collateral ligament
Fan shaped
lateral epicondyle to annular ligament
primary restraint to varus/ supination
lateral ulnar collateral ligament
lateral epicondyle to supinator crest, ulna, and annular ligament
tight extreme flexion and any varus
secondary restraint to varus/supination
annular ligament
Restraint- traction, lateral subluxation
Secondary restraint to varus/supination
Axis of motion for the elbow
movement is through center of trochlea and capitulum
medial trochlea More distal
Carrying angle is about 13°
mediately deviate with flexion
Laterally deviate with extension
Increased angle may impact ulnar nerve
Limits to elbow extension
anterior capsule
Flexor muscles
Bony olecranon process
limits to elbow flexion
soft tissue
Posterior capsule
Extensor muscles
Bony- Radial head and coronoid process
Function limited with forearm in mid to full pronation
humero ulnar joint positions
closed- full extension and supination
Open - 70° flexion and 10° supination
humeroradial joint positions
closed- 90 degrees flexion 5° supination
Open -full extension and supination
closed and open pack positions during elbow injury
Closed packed joints often fracture associated bones
Open packed joints often dislocate
monteggia fx
fx proximal ulna
radial head dislocation
role of interosseous membrane
binds radius to ulna
muscle attachments
Transfers force from radius to ulna
Wight bearing from hand to forearm is through
the radius
The interosseous membrane distributes portion load to ulna
Axis of motion for proximal and distal radio ulnar joints
Radial head through ulnar head
proximal radial ulnar joint
within capsule with HU and HR joints
Annular ligament
Annular ligament
allows spin
Binds radius to ulna
Prevents radial head displacement
distal radioulnar joint
palmar RU lig
dorsal RU lig
articular disc
palmar RU lig
tight in supination
dorsal RU lig
tight in pronation
articular disc (TFCC)
binds to distal radius ulna
dual articular surface
separates RU and RC joints
central portion avascular
RU joint arthro
pivot
one dof
rom-150
pronation- 75
supination-85
functional- 50 each
capsular pattern- pro> sup
pronation at RU jt
radial head spins in annular lig/radial notch
radius rotates over ulna
supination at RU
radial head spins in annular ligament radial notch
radius unwinds from ulna
treatment considerations for PRU and DRU
PRU- roll glide opposite (it only spins)
DRU- roll glide same
limits to supination
pronator teres
pronator quadratus
TFCC
palmar DRUJ
IOM
limits to pronation
supinator
biceps
TFCC
dorsal DRUL lig
brachialis
prime mover- inserts close to joint of action
unaffected by forearm position due to insertion on ulna
biceps brachii
prime mover
most effective 80-100 elbow flexion and with shoulder in extension
good supinator at 90 flexion
brachioradialis
stability muscle - inserts far from joint of action
strongest at 90-120 elbow flexion with forearm in mid position
pronator teres
small role in elbow flexion
triceps
not influences by forearm position due to ulnar insertion
max torque 90 flexion
primarily medial head lateral and long head active with higher resistance or speed of contraction
anconeus
helps initiate elbow extension
may stabilize against varus force
supinator
supinator
functions regardless of elbow position
biceps brachii- supination
used with higher force activity and when combined with flexion
good supinator at 90 flexion
radial wrist extensors
supination
brachioradialis
can derotate forearm to neutral
forearm pronators
pronator teres
pronator quadratus
flexor carpi radialis
palmaris longus
brachioradialis
