Elbow and forearm Flashcards
describe the osteology of the forearm
3 bones/4 joints
humeral-ulnar
humeroradial
proximal/distal radio-ulnar
t/f
flexion/extension and supination/pronation of the forearm si independent of each other in the GH joint
true
describe the trochlear notch
jawlike
has longitudinal crest
which ligament in the body runs from the ulna to the ulna
MCL transverse fibers
describe the radial head
disc-like
articular cartilage covers at 280 degrees of the rim
contact radial nots on ulna
describe the fovea
what does the fovea articulate with
shallow cup-shaped depression
articulates with capitulum
what motions does the humero-ulnar joint contribute to
flexion/extension
contributes to much of the stability
what motions does the humeroradial joint contribute to
flexion/extension
ligaments buttress the radial head against the capitulum
does the ulna have axial rotation
yes, modified hinge joint
how does the medial lip of the trochlea affect flexion/extension of the elbow
medial lip of trochlea is larger so ulna deviates laterally relative to humerus
what is the frontal plane angle called in regard to elbow flexion/extension
normal cubitus of carrying angle
what is the average normal cubitus valgus or carrying angle
when is it higher
13 degrees
higher on dominant side, higher with age
what is excessive cubitus valgus or carrying angle
20-25 degrees
cubitus varus secondary to growth plate injury
what ligaments are present in the elbow joint
medial collateral ligament (MCL)
radial collateral ligament (RCL)
lateral collateral ligament (LCL)
annular ligament
describe the MCL anterior fibers
-strength
-resists
-how does it run
-function
strongest
resists valgus
medial epicondyle to coronoid process
9 separate divisions
stability in sagittal plane
describe the MCL posterior fibers
-location
-where does it run
-what does it resist
fan-like thickening of posterior/med capsule
medial epicondyle to olecranon
resists valgus forces and tight in extreme flexion
describe the MCL transverse fibers
-where does it run
-what does it limit
olecranon to coronoid process (ulna to ulna)
only limited articular stability
explain how a WB injury to the MCL can occur
what injuries can occur
extended and valgus force WB
can cause compression fracture, ulnar nerve injury
anterior capsule, medial musculature at epicondyle
explain how a NWB injury to the MCL can occur
repetitive valgus producing strain, overhead athletes
most common in baseball pitchers d/t late cocking and acceleration phase
what is tommy john surgery
repair of the anterior fibers through a tendon graft from palmaris longus, gracilis, or plantaris
what 3 structures does the RCL merge with
annular ligament
supinator
extensor carpi radialis brevis (ECRB)
describe the lateral ulnar collateral ligament (LUCL)
-attachment site
-when is it taut
-what structure is the guidewires in frontal plane
thicker
attaches supinator crest of ulna
taut in full FXT
MCL are guidewires in frontal plane during full FLX/EXTn
when is intracapsular pressure the lowest or the “position of comfort”
what does the “position of comfort” mean
80 degrees flexion
pts with swollen elbow may hold this position, but may get a flexion contractor
what is the terrible triad injury
fall on outstretched/supinated arm
elbow joint dislocation (ligament injury)
fracture on radial head or coronoid process
can problems occur with surgery on the elbow
if so, what injuries are common
yes
persistent instability, nerve damage, heterotropic ossification, stiffness
when can a flexion contracture occur
after immobilization
heterotropic ossification
osteophyte formation
inflammation/effusion elbow joint
muscle spasticity
triceps paralysis
scarring of the skin anterior elbow
what is the functional arc of the elbow
145-150 flexion
-5 degrees extension
what is the primary plane of motion of the humero-ulnar joint
saggital
explain full extension of the humero-ulnar joint
extensible anterior tissues and some fibers MCL
olecranon process able to wedge into olecranon fossa
explain flexion of the humeral-ulnar joint
concave surface of trochlear notch rolls and slides on convex trochlea
elongation fo ulnar nerve
posterior MCL
where does motion occur with the humeroradial arthrokinematics
what are the arthrokinematics
between cuplike fovea of radial head and capitulum
radius rolls and slides
describe the active flexion of the humeroradial arthrokinematics
radial fovea pulled against capitulum by contracting muscles
humeroradial joint provides __% lateral stability
50%
t/f
changes with the radial head such as fracture, malunion, surgical removal change valgus alignment
true
what is the function of the interosseous membrane
radius and ulna bound together
attachment site
transmits force to share load
the tensile strength of the interosseous membrane is similar to what other structure
patellar tendon
a tear of the interosseus membrane will result in..
proximal migration fo radius
what structure connects the ulna to the humerus
interosseus membrane
in full pronation, how does the radius and ulna move
radius crosses over the ulna
where is the axis of rotation located in the FA during pronation
obliquely across the forearm from radial head to ulnar head
what causes a “pulled elbow”, “nursemaids elbow”, or “babysitter’s elbow”
strenuous pull on pronated hand causes radial head to slip out
what makes up the distal radio-ulnar joint
convex head of ulna on shallow concave radius
triangular fibrocartilage (TFC) holds head of ulna
what are the stabilizers of the distal radio-ulnar joint
triangular fibrocartilage (TFCC)
pronator teres
ECU tendon
distal oblique fibers interosseous membrane
what is the average motion of pronation/supination
pronation: 75 degrees
supination: 85 degrees
t/f
supination/pronation both require simultaneous movements at only proximal or distal radio-ulna joint or humeroradial joint
false
supination/pronation both requires simultaneous movements at both proximal and distal radio-ulna joint and humeroradial joint
what happens during supination with the radius and carpal bones
radius and carpal bones rotate around the fixed humerus and ulna
proximally, describe supination
rotation of radial head in fibro-osseus ring
no slide/roll
distally, describe pronation
radius rolls/slides in the same direction
articular discs proximal surface slides across ulan head
during pronation, how do the radius and carpal bones move
radius and carpal bones rotate around the fixed humerus and ulna
where is the axis of rotation located during rotation
axis is nearly parallel to membrane
limits tension
t/f
the humeroradial joint is linked with any movement of elbow and forearm
true
how does the fovea of the radial head move during pronation
the fovea of the radial head spins against the capitulum
how does the pronator teres function during forearm pronation
pronates the forearm
pulls radius proximally against the capitulum
when the forearm is fixed distally during pronation (pushup position), what are the ulna/radius movements
what muscles are involved
is this a closed/open chain exercise
ulna rotates around the foxed radius
infraspinatus and pronator quadratus
closed chain
what is the innervation of the brachialis
what is the innervation of the brachialis
what elbow flexors are innervated by the musculocutaneous nerve (C5-C6)
brachialis, biceps
what forearm supinators are innervated by the musculocutaneous nerve (C5-C6)
biceps
what elbow flexors are innervated by the radial nerve (C5-C6)
bracioradialis
what elbow flexors are innervated by the median never (C6-C7)
pronator teres
what elbow extensors are innervated by the radial nerve (C7-C8)
triceps
anconeus
what forearm pronators are innervated by the median nerve
pronator quadratus
pronator teres
what forearm supinators are innervated by the radial nerve
supinator
