Ulna and Radius Elbow Complex
what is the function of the brachialis
elbow flexion: regardless of the position of the forearm
where is the medial/ulnar collateral ligament
extends from medial epicondyle of humerus to the coronoid process and olecranon of the ulna
what does the proximal radioulnar joint allow
rotation to occur: supination and pronation
what muscles are activated first until more torque is needed
shorter muscles or muscles that cross only one joint
where does compression injury occur
occurs at the elbow joint during a fall on our hand with elbow in closed-packed position
olecranon process
posterior surface: bursa anterior surface: part of trochlear notch
what are the two types of pronators
pronator teres pronator quadratus
what is the function of the humeroulnar joint
provides majority of structural stability to the elbow
what is the function of the medial/ulnar collateral ligament
provides the most significant resistance against a valgus force at the elbow
what are the additional joints of the forearm
proximal radioulnar joint distal radioulnar joint
what percent of compression force is through the ulna
20%
what percent of compression force is through the radius
80%
what happens when the pectorals major acts as elbow extensor
GH jt adducts, horizontally flexes, pull the humerus towards the midline
what is the humeroulnar joint enclosed by
a joint capsule
what is the smaller extensor muscle
anconeus
which fibers are the strongest and stiffest of the medial/ulnar collateral ligament
anterior
what does the medial/ ulnar collateral ligament consist of
anterior, posterior, and transverse fiber bundles
supinator notch
between supinator crest and the distal part of the coronoid process
what is a powerful supinator
biceps brachii
what are the different types of elbow flexors
biceps brachii brachioradialis brachialis
what is known as the work horse of elbow flexion
brachialis
what muscle usually generates the greatest force of any muscle crossing the elbow
brachialis
what is an example of the biceps as a flexor
bringing spoon to mouth
what does the brachioradialis do
can be readily palpated during resisted elbow flexion with forearm in neutral
what is elbow dislocation
caused by a distraction force exerted on the radius
who is most susceptible for elbow dislocation
children: nursemaid's elbow
where does the humeroulnar joint articulate
concave, trochlear notch (ulna) around the convex trochlea (humerus)
what does the distal radioulnar joint consist of
convex head of ulna fitting into a shallow concavity on the radius (ulnar notch)
what is the carrying angle of the elbow called
cubitus valgus
where does the humeroradial joint articulate
cuplike fovea of radial head and the rounded capitulum (humerus)
where is the ulnar notch of the radius
distal end of radius which accommodates the head of the ulna
what happens during pronation at the proximal radioulnar joint
distal segment of the radius rotates and crosses over a fixed ulna
where does the shaft of radius enlarge
distally whereas ulna shaft decreases distally
what does the anconeus do
first to initiate and maintain low level of elbow extensor force due to law of parsimony
what is the function of the annular ligament
fits snugly around the head of radius and holds against the ulna
______ are 2x as strong as ______ in all positions
flexors, extensors
what doe the interosseous membrane allow
for transmission of forces through the upper limb
what is compression injury
force from the fall transmits force through either the radius or ulna
what is triceps paralysis
fracture of cervical spine may result in C6 quadriplegia
what is a valgus injury
fully extended elbow receives a violent valgus force
where is the lateral/radial collateral ligament seen
goes from the lateral epicondyle and blends into the annular ligament and supinator crest of the ulna
what is excessive cubits valgus
greater than 20 degrees
what does the pronator teres do
has 2 heads: humeral and ulnar primary forearm pronator
what is part of the radius
head of radius shaft of radius distal end of radius
what does the interosseous membrane do
holds the radius and ulna together
what are the different joints at the elbow
humeroulnar humeroradial
what does the proximal radioulnar joint share the same joint capsule with
humeroulnar joint and humeroradial joint
when is a valgus injury commonly seen?
in a fall or when pitching a baseball, results in overstitching of the medial collateral ligament
what happens at rest with the humeroradial joint
in full extension, little if any physical contact exists at the humeroradial joint
ulnar tuberosity
inferior side of coronoid process
supinator crest
inferior to radial notch on lateral surface of ulna
what is the brachioradialis
longest elbow muscle
what does the triceps function as in elbow extensor
large and powerful provides stability at elbow produces majority of total extensor torque at elbow during maximal extensor effort
where is the radial styloid process
lateral aspect of radius
radial notch of ulna
lateral side of coronoid process, receives head of radius
head of ulna
lateral surface articulates with ulnar notch of radius styloid process of ulna
what is cubits varus
less than 5 degrees
where is the brachialis
lies deep under biceps muscle
what is the posterior surface of the radial shaft called
lister's tubercle which forms tunnels for extensor tendons
where is the annular ligament and what is composed of
located a proximal radioulnar joint thick circular band of connective tissue
what is a supinator
located deep on the dorsal side of the forearm relentless forearm supinator during elbow flexion
how many heads are in the triceps and what are they
long, medial, lateral
biceps brachii: flexor- what does it do
may be palpated when elbow is flexed and forearm is supinated simultaneously performs elbow flexion and supination for the forearm
what happens if the ulna is fallen on in a compression injury?
may cause fracture of coronoid or olecranon process
what happens if the radius is fallen on in a compression injury?
may cause fracture of the radial head
what is the humeroulnar joint stabilized by
medial collateral ligament
what does the pronator quadratus do
most active and consistently used pronator- regardless of power demands
what about the fibers of the interosseous membrane?
most are directed away from the radius to the ulna
what is the law of parsimony
nervous system tends to activate the fewest muscles or muscle fibers possible for the control of a given joint
what is cubitus valgus do
normal carrying angle of the elbow approximately 10-20 degrees abduction keeps carried items away from the side of the thigh while walking
what does the biceps brachii do as a supinator
normally recruited during high power supination activities, especially those associated with elbow flexion
what type of joint capsule is the elbow joint
one joint capsule
what can act as elbow extensor in a closed kinematic chain
pectoralis major
what does the distal radioulnar joint do during pronation and supination
stabilizes the distal forearm
what is the function of the lateral/radial collateral ligament
stabilizes the elbow against a vagus-directed force
coronoid process
superior surface- forms a part of the trochlear notch
what is part of the head of radius
superior surface: articulates with capitiulum of humerus circumference radial neck: distal to head radial tuberosity: distal to medial part of neck
what is the first muscle to initiate supination at low to moderate intensity supination activities
supinator
what happens to the ulna and radius when the forearm is fully supinated at the forearm
the radius and ulna are parallel
what does the distraction cause
the radius to slip out of the annular ligament
what would be paralyzed in triceps paralysis
triceps (C7) and other shoulder muscles such as pectorals major (C5-C6) would remain innervated
what are the elbow extensors
triceps brachii anconeus
what is consisted of the ulna
trochlear notch olecranon coronoid process shaft of ulna head of ulna ulnar tuberosity radial notch of ulna supinator crest supinator fossa
some the force through the radius is transferred to what via the membrane
ulna
what is the differences between men and women in carrying angle
women is greater due to different angle in pelvis for childbirth enables women to fit their upper arms in close to waist when carrying items
example: getting into bed (triceps paralysis)
wrist fixed to bend, the muscles rotate elbow into extension once locked into extension, the stable elbow allows the entire limb to accept weight without buckling