Lecture 11 and 12: Elbow and Forearm Final. NEED TO FINISH Flashcards
how many bones/joints make up the forearm
3 bones and 4 joints
humeri-ulnar
humeroradial
radio-ulnar
goal of forearm joints
placement of hand
what motions are independent of one another in the forearm/wrist
flexion and extension and supination and pronation are independent of one another and the GH joint
what would you palpate at the medial and lateral epicondyles
lateral = common extensor/supinator tendon
medial = common flexor/pronator tendon
describe the trochlea
like a rounded empty spool of thread
medial and lateral borders flare up to form lips
trochlear groove is between the lips and spirals towards the medial side
medial lip flares/projects further distally
describe the trochlear notch
jawlike
has a longitudinal crest
what attaches to the tuberosity of the ulna
brachialis
what attaches to the supinator crest
LCL/sup mm
how is the radius positioned in supination
parallel and lateral
describe the ends of the radius; which is bigger/smaller
proximal end is small
distal end is large = major part of wrist; styloid process
describe the radial head
disc like
articular cartilage covers at 280 degrees of the rim
contacts the radial notch on the ulna
what is the fovea of the radius
shallow cup shaped depression on radial head that articulates with capitulum
contributions of the humeroulnar joint
contributes to flexion and extension
contributes to much of the stability of the elbow
contributions of the humeroradial joint
contributes to flexion and extension
ligaments press the radial head against the capitulum
what type of joint is the elbow (humeroulnar)
originally thought to be a hinge joint but it is actually a modified hinge joint because the ulna actually has a small amount of axial rotation
where is the axis od the elbow for flexion and extension
near med-lat
lateral epicondyle through convex members
medial lip of trochlea is longer so the ulna deviates laterally
what is the frontal plane angle of the elbow
normal cubitos valgus or carrying angle
average is 13 degrees
excessive = 20-25; cubitus varus secondary to growth plate injury
what joints does the capsule around the elbow encompass
humeroulnar
humeroradial
radioulnar
what are the periarticular tissues of the elbow
capsule
MCL
RCL
LCL
annular ligament
describe the anterior fibers of the MCL
strongest
resist valgus
run from medial epicondyle to coronoid process
provides stability in the sagittal plane; 9 separate divisions
describe the posterior fibers of the MCL
fan like
thickening of posterior/med capsule
from medial epicondyle to olecranon
resist valgus
tight in extreme flexion
describe the transverse fibers of the MCL
from olecranon to coronoid process
only limited articular stability
how can a WB injury to the MCL occur
extended and valgus force
can cause compression fx, ulnar nerve injury, anterior capsule injury, or damage to medial musculature at the epicondyles
how can a NWB injury to the MCL occur
repetitive valgus produces strain
common with overhead athletes
may require “Tommy John surgery”
what is Tommy John surgery
repair of the anterior fibers through a tendon graft from palmaris longus, gracilis, or plantaris
where does the lateral collateral ligament complex run
2 primary bundles that run from the lateral epicondyle
resist carbs forces
describe the radial collateral ligament
merges with the annular lig, supinator, and ECRB
describe the lateral ulnar collateral ligament
thicker
attaches to supinator crest of ulna
taut at full flexion
guide wire with MCL in frontal plane during full flexion/extension
sling for the radial head
when is intracapsular pressure at the elbow lowest
at 80 degrees flexion
“position of comfort”
those with a swollen elbow may hold this position, but there is a possibility of a flexion contracture
what is a terrible triad injury
fall outstretched and supinated
elbow joint dislocation
fx radial head
fx coronoid process
problems can occur even with surgery… like persistent instability, nerve damage, heterotypic ossification, and stiffness
ROM for elbow flexion/extension
5 degrees beyond neutral (5 degrees hyperextension)
145-150 flexion
“functional arc”
what happens fi there is a spinal cord injury above C5
paralysis of elbow flexors
what can result in a flexion contracture
immbolixation
heterotrophic ossification
osteophyte formation
inflammation/effusion elbow
muscle spasticity
triceps paralysis
scarring of skin on anterior elbow
describe the arthrokinematics of the humeroulnar joint
concave trochlear notch of ulna and convex trochlea of humerus
primarily sagittal plane
ext = olecranon process wedged into olecranon fossa; extensible anterior tissues and some fibers of MCL
flex = concave trochlear notch tolls and slides on convex trochlea; elongation of ulnar n and posterior MCL
what does the coronoid process do with full elbow flexion
coronoid process fits into the coronoid fossa of the humerus
arthrokinematics of the humeroradial joint
between the cuplike fovea of the radial head and the capitulum
radius rolls and slides
flexion = radial fovea is pulled firmly against the capitulum by contracting muscles
minimal stability in sagittal plane
50% lateral stability to valgus forces
changes with the radial head
structure if the interosseous membrane
radius and ulna bound together
central band is directed distally and medially at 20 deg from radius
tensile strength similar to patellar tendon
oblique cord is perpendicular
function of interosseous membrane
central band: attachment site, binds, provides mechanism for force transmission,
transmits muscle forces to radiohumeral joint 3-4x BW
force shunted to radio ulnar joint
membrane tears = migration of radius
describe the force transmission of a compressive force through the hand
transmitted through wrist at RC jt
goes to radius
force pulls central band of interosseous membrane taut
this tranfers a significant amount of force to ulna and then across humeroulnar joint
compressive forces finally transmitted to shoiulder
describe the force transmission of holding a load (distracting force)
distraction slackens central band of interosseous membrane
oblique cord, annular ligament, and brachioradialis assist to support load
