Elbow Injuries
July/August 2013 issue of Radiologic Technology
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Introduction
The elbow is a complex joint that supports forearm movement and
consequently is at risk for various injuries and disorders. Elbow
disorders can range from chronic to acute problems, many of which
can be debilitating.
This article explains the functional anatomy of the elbow joint and
discusses the most common elbow disorders and injuries. It also
presents the most common diagnostic imaging choices, along with
typical acquisition methods.
Elbow
The functionality of the upper extremity relies on elbow motion. If a
person’s elbow motion decreases by 50%, upper extremity
impairment increases by as much as 80%. The elbow controls
pronation, supination, flexion, and extension of the forearm.
Pronation positions the forearm with the palm facing down and the
arm extended. This position causes the paths of the radius and ulna
to cross at the midpoint of the shafts. Supination of the forearm
brings the palm of the hand face up with the forearm extended. This
position brings the radius and ulna parallel with each other.
Elbow
The elbow joint’s ability to flex and extend depends on the articulation
of the ulna and humerus. Pronation and supination depend on the radial
head and capitulum of the humerus. A fully working elbow should allow
the forearm to extend 145°from full extension to full flexion and
permit a 180°rotation during pronation or supination.
Elbow pain can be caused by a number of issues with the joint or
surrounding anatomy. Pain at the elbow also can result from problems
not related to the elbow joint, such as cervical radiculopathy or referred
shoulder pain. Most commonly, elbow pain is due to periarticular causes
or problems specific to the elbow joint. Polyarticular causes, or problems
affecting many joints, also play a role in elbow disorders. Chronic elbow
injuries can be attributed to repetitive motion of the joint or
inflammatory processes. Acute injuries occur from trauma, most often
from falls.
Functional Anatomy
The humerus, radius, and ulna are the 3 bones that make up the
elbow. Each bone is designed to allow the elbow to act as a hinge
joint. The distal humerus contains the trochlea, capitulum, coronoid
fossa, olecranon fossa, radial fossa, medial epicondyle, and lateral
epicondyle. The proximal radius includes the radial head, radial neck,
and radial tuberosity. The proximal ulna comprises the olecranon
process, coronoid process, radial notch, and trochlear notch.
Within the elbow are the ulnohumeral, radiocapitellar, and radioulnar
joints, all of which lie within the same joint capsule. The capsule has
an internal synovial layer and a superficial fibrous layer. Within these
layers are 3 fat pads. The coronoid fossa and radial fossa both contain
an anterior fat pad, and the olecranon fossa has a posterior fat pad.
Functional Anatomy
The largest of the elbow joints is the ulnohumeral articulation, which is a
modified hinge joint. The trochlear groove of the humerus holds the
ulnohumeral articulation, which allows for movement between the ulna and
the humerus.
The radiocapitellar joint is a ball and socket joint composed of the radial
head and humeral capitulum. This joint is lateral to the ulnohumeral joint
and allows for forearm supination and pronation.
The radioulnar joint is a pivot type of synovial joint (a freely movable joint
that contains fibrocartilage and hyaline cartilage layers and synovial fluid)
divided into superior and inferior sections. The superior section contains the
articulation between the radial head and the radial notch of the ulna; the
joint rotates within the annular ligament during pronation or supination.
The inferior section articulates with the ulnar notch of the radius and
swivels around the head of the ulna during pronation or supination.
Functional Anatomy
The olecranon process is the bony prominence of the ulna and also is
where the triceps muscle attaches to the elbow joint. The olecranon
bursa is a fluid-filled sac that provides a cushion between the bone
and the slack skin directly over the olecranon process. The
bicipitoradial bursa, or cubital bursa, lies between the radial
tuberosity and the biceps tendon. The interosseous medial bursa lies
medially between the bicipitoradial bursa and the interosseous
membrane of the forearm.
Below the neck of the radius, the radial tuberosity lies at the insertion
point of the biceps tendon. The brachialis muscle attaches at the
coronoid process, whereas the radial notch articulates with the radial
head to provide radial head stabilization.
Elbow Ligaments
Ligaments provide stability for the elbow joint. The medial and lateral
collateral ligaments supply most of the stabilization. The medial
collateral ligament (MCL) attaches the ulna to the medial epicondyle
of the humerus. The annular ligament loops around the radial head.
The lateral ligament attaches the lateral epicondyle to the annular
ligament.
The MCL also is called the ulnar collateral ligament (UCL); it has 3
separate bundles and is essential to stabilizing the ulnohumeral
articulation of the elbow. The ligament bundles are the anterior,
transverse, and posterior bundles. The most important of the elbow
stabilizing ligament bundles is the anterior bundle.
Elbow Ligaments
The lateral collateral ligament has 4 separate structures: the annular
ligament, the accessory lateral collateral ligament, the lateral ulnar
collateral ligament, and the radial collateral ligament.
The annular ligament encompasses the radial head and stabilizes the
radial notch of the ulna by banding the proximal radius to the
proximal ulna. The accessory lateral collateral ligament derives from
the inferior portion of the annular ligament and connects to the
supinator crest of the ulna. The lateral ulnar collateral ligament begins
at the lateral epicondyle and also attaches to the ulna’s supinator
crest. The radial collateral ligament begins at the lateral epicondyle
and inserts into the annular ligament.
Elbow Muscles
Four muscle groups, as well as the tendons, work together to move
the elbow joint. The muscle groups are flexors, extensors, the
extensor supinator group, and the flexor pronator group. Three
muscles within the flexor group primarily act upon the elbow: the
biceps brachii, the brachioradialis, and the brachialis muscles. The
brachialis muscle and the biceps brachii are the most powerful elbow
flexor muscles.
The extensor group contains the triceps and anconeus muscles. The
triceps muscle and part of the anconeus muscle control forearm
extension. The extensor supinator group contains the brachioradialis,
supinator, extensor digitorum, extensor carpi radialis longus and
brevis, extensor carpi ulnaris, and extensor digiti minimi. The flexor
pronator group includes the pronator teres, flexor carpi radialis,
palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis.
Blood Supply and Elbow Nerves
The blood supply through the elbow is extensive, and the major
arteries involved with the elbow are the brachial artery, radial artery,
and ulnar artery. The brachial artery is lateral to the median nerve
and lies within the cubital fossa of the elbow. Within the cubital fossa,
the brachial artery then bifurcates into the radial and ulnar arteries.
Four nerves control elbow function and sensation. They are the
musculocutaneous nerve, median nerve, ulnar nerve, and radial
nerve. The brachial plexus of the elbow is very complex, filled with a
network of peripheral nerves. The most accessible nerve is the ulnar
nerve. This nerve sits along the olecranon groove and crosses the
elbow through the cubital tunnel of the humerus. Because of its
location, the ulnar nerve is the elbow nerve injured most often. It
most commonly is compressed during direct trauma.
Blood Supply and Elbow Nerves
The radial nerve crosses the elbow forward of the lateral epicondyle.
Radial nerve compression also is possible because the nerve is
susceptible to tightening of the fibrous band that surrounds it.
The median nerve runs medially to the biceps tendon and crosses the
elbow from within the antecubital fossa. At the elbow, the posterior
interosseous nerve branches off of the radial nerve. The
musculocutaneous nerve traverses the elbow through the lateral
antecubital fossa.
Bone Development
Bones develop in 3 distinct stages: during childhood, adolescence,
and young adulthood.
When viewing a radiograph of a pediatric patient’s elbow, it is
important to understand the ossification centers or the order in which
the elbow joint and bones begin to develop. The order of bone
growth is the same for all pediatric patients, and the commonly
accepted mnemonic for this order is CRITOE (capitulum, radial head,
internal [medial] epicondyle, trochlea, olecranon process, and
external [lateral] epicondyle). Ossification centers typically appear in
girls 1 to 2 years before they appear in boys.
Radiographic Anatomy
Radiographically, several important anatomical lines are essential in
assessing possible elbow damage in patients. The radiocapitellar line
should be centered through the long axis of the radius and extend
through the radial neck to the center of the capitulum.
A lateral radiograph also should display the anterior humeral line. This
line should begin at the anterior portion of the humerus and extend
vertically through the middle third of the capitulum. The coronoid line
also can be seen on the lateral image. This line should proceed from
the top of the coronoid process of the ulna and proximally intersect
the anterior portion of the capitulum and trochlea.
Radiographic Anatomy
The lateral projection of the elbow also is essential in evaluating the
fat pads. The distal humerus contains 2 fat pads that make contact
with the joint capsule on the anterior and posterior portion of the
joint. Radiographically, this fat pad appears as a darker density next to
the bone with a grayer density of tissue surrounding the edges. If the
posterior fat pad is noted by the radiologist, this is known as a
positive fat pad sign and indicates a probable fracture in
approximately 90% of fracture cases.
Fat pads appear in the presence of a joint effusion when the capsule
that holds the fat pads distends. Correctly positioning the patient’s
elbow at 90°is imperative when imaging fat pads. A minor extension
of the arm can increase the pressure on the posterior fat pad, making
the fat pad appear on the image and leading to a false-positive
diagnosis.
Diagnostic Imaging Modalities:
Radiography
The most common findings are fractures, arthritis, loose bodies, and
destructive processes. Radiologic technologists should obtain a
minimum of 2 projections with 90°of differentiation because the
elbow anatomy appears normal in some projections even when the
patient has a disorder or injury in the area.
For the elbow, an anteroposterior (AP) projection and a lateral
projection should be taken. Other common elbow projections include
the medial and lateral oblique, radiocapitellar, and the Jones method,
also known as the distal humerus acute flexion projection.
Radiography
In the AP projection, the patient’s elbow is extended over the
cassette. Supination of the hand prevents the forearm bones from
crossing. A slight lateral tilt of the forearm can place the anatomy in
the correct position. The x-ray beam is perpendicular and centered to
the elbow joint.
When the patient cannot completely straighten the elbow, 2 images
replace the AP projection. Positioning for both projections is similar to
the AP projection, in that the central ray is perpendicular to the joint.
However, the first projection places the posterior surface of the
humerus flat and parallel to the cassette. For the second projection,
the technologist places the patient’s arm so that the posterior
forearm is flat and parallel to the cassette.
Radiography
Lateral images of the elbow require that the patient flex the elbow
90°. Both the forearm and the humerus should be parallel to the
surface of the cassette during contact, and the radiologic technologist
should rotate the patient’s hand into a true lateral position. The
central ray should be directed perpendicular to the elbow joint.
The medial oblique projection requires the patient to extend the
elbow over the cassette as in the AP projection but with the arm and
hand in a pronated position. The internal oblique projection is
positioned similarly, but the arm should be rotated laterally until the
elbow is at a 45°angle to the cassette.
Radiography
The radiocapitellar projection requires that the forearm be imaged
using a lateral projection but that the hand and arm remain in a
neutral rotation. The x-ray beam points at a 45°cephalic angle
toward the shoulder, centering on the elbow joint. The radiocapitellar
projection shows an oblique angle of the lateral elbow separating the
proximal radius and ulna.
The Jones method acquires images of the elbow in complete flexion.
The posterior aspect of the humerus lies on the cassette with the
forearm superimposed over the top. The x-ray beam should be
perpendicular to the cassette and centered approximately 2 inches
above the olecranon process.
Magnetic Resonance Imaging
Magnetic resonance (MR) imaging helps display the joint’s muscle
and tendon attachments. The ability to evaluate much of the elbow
anatomy would make MR an optimal imaging choice except that
positioning the elbow is difficult using MR imaging.
For elbow MR, the patient can lie on his or her stomach with the arm
positioned above the head. Patients do not tolerate this position well;
therefore, the supine position is used more frequently.
The classic MR acquisition for the elbow involves axial, coronal, and
sagittal images with T1- and T2-weighted images.
Magnetic Resonance Imaging
MR images of the 3 major nerves of the elbow generally appear the
same intensity as muscle on T1-weighted imaging. The signal intensity
is slightly higher with T2-weighted images, but outlining and
visualizing the nerves depend somewhat on adjacent fat.
MR images of an injured ligament might show thickening or thinning
of the ligament, increased signal intensity, hemorrhage, slackness,
and other abnormalities. Muscle injuries on MR scans show
morphological changes, atrophy, fatty changes, and edema. Joint
fluids increase with diseases that produce synovial inflammatory
changes. MR using gadolinium contrast enhances the tissue’s signal
intensity.
Computed Tomography
The rapid scanning and helical imaging of modern CT scanners make
accurate and prompt imaging of elbow trauma possible. Planning for
elbow surgery also benefits from CT’s ability to reformat images in
any plane required and to provide 3-D volume renderings.
CT displays fractures, loose bodies, osteochondral lesions, and other
bony abnormalities well. Aside from fracture fragment evaluation, CT
with IV contrast also is beneficial for blood vessel evaluation following
trauma. Similar to conventional arthrography of the elbow, CT
arthrography can highlight the joint capsule and filling defects from
synovitis or loose bodies. CT arthrography also is helpful in evaluating
MCL tears.
Ultrasonography
Ultrasonography is not a typical choice for imaging the elbow, but the
modality offers a less expensive alternative for evaluating tendons,
ligaments, and nerves. Ultrasonography is useful in diagnosing softtissue diseases of the elbow. It is also a good choice when imaging
infants and young patients to evaluate unossified epiphyses that
might not be noticeable on radiographs.
Color-flow Doppler imaging can highlight soft-tissue inflammation by
showing increased blood flow to areas of the elbow. Doppler imaging
also can help distinguish cystic from solid masses by displaying the
vascular components of the mass.
Ultrasonography is useful for guiding aspiration needles or during
therapeutic measures for the elbow.
Elbow Disorders: Olecranon
Bursitis
Inflammation of the olecranon bursa is called olecranon bursitis. It is
also referred to as student’s elbow because the condition can be
caused by leaning excessively on the elbow. Chronic olecranon
bursitis is seen in people who throw repetitively, such as baseball
pitchers; acute cases usually occur after a direct fall onto a hard
surface.
Patients with bursitis are easily identified by the large amount of
swelling and masslike appearance of the elbow. In nontraumatic
situations, imaging may not be required if the bursa fluid can be
aspirated. In traumatic situations, however, the bursa can become
inflamed because of an olecranon fracture. Fluid aspiration
sometimes leads to infection, and continued pain should be
investigated with further imaging studies.
Cubital Bursitis
Cubital bursitis also is known as bicipitoradial bursitis, and symptoms
include antecubital fossa swelling and tenderness.
MR imaging of cubital bursitis shows high-signal fluid that emerges
between the radial tuberosity and biceps tendon distally. The fluid
normally appears on T2-weighted images, which can lead to
misdiagnosis of a soft-tissue tumor. In questionable cases, IV contrast
assists in the diagnosis. If the fluid collection does not enhance,
bursitis is the likely diagnosis.
During sonography, elbow extension is routine. Sonograms of cubital
bursitis can show fluid or hypoechoic tissue that causes active
distention of the bicipitoradial bursa. Doppler imaging shows an
increase in blood flow to the area, which is symptomatic of active
inflammation.
Tendonitis and Tendon Tears
Tendonitis of the elbow is due to inflammation of the tendons. Tendonitis of
the biceps muscle can lead to rupture on either end. This condition
commonly occurs after lifting heavy objects and results in tenderness near
the biceps rupture site. On average, tendonitis of the biceps occurs in men
aged 45 to 60 years.
When the distal end of the biceps muscle ruptures, symptoms include
proximal elbow pain and weakness, especially during supination. When the
rupture occurs, the patient can experience a snapping sensation followed by
the appearance of a bulbous deformity, or “Popeye sign,” near the distal
bicep.
Radiographs may show an avulsion fracture of the radial tuberosity in cases
of complete tears, but enlargement or abnormality of the radial tuberosity
is the most common finding. MR imaging is useful to assess a possible tear
or degeneration of the biceps tendon. Ultrasonography may be helpful in
determining the extent of any tears.
Tendonitis and Tendon Tears
Triceps tendonitis is common with repetitive elbow use in young
athletes. The individual often experiences a sensation on the medial
border of the elbow that patients describe as something snapping
into place.
As with bicep tears, MR and ultrasonography images can help
physicians distinguish tears from other pathology.
Lateral Epicondylitis
Lateral epicondylitis is the most common sports-related injury of the
elbow and a primary cause of elbow pain. The mechanism of injury
depends on repeated, forceful contraction of the wrist extensor
muscles; contraction occurs with frequent forearm pronation and
supination, along with wrist extension. The abuse of the extensor
muscles causes inflammation at the lateral epicondyle.
Lateral epicondylitis is frequently referred to as tennis elbow.
Although the condition is associated with tennis, many other
repetitive motions can cause epicondylitis. Estimates show that 90%
of lateral epicondylitis patients develop the disorder from activities
other than tennis.
Lateral Epicondylitis
The pain felt with lateral epicondylitis normally occurs at the lateral
epicondyle or slightly outside the elbow. Gripping items may become
difficult because of weakness and increased pain within the forearm.
This is known as the “coffee cup” sign.
Radiographic evidence of lateral epicondylitis is rarely found. In any
case, radiographs differentiate lateral epicondylitis from other disease
processes of the elbow such as arthritis or loose bodies.
Lateral Epicondylitis
Regardless of whether the tendonosis is located medially or laterally,
MR imaging demonstrates the same epicondylitis features on either
side. Ultrasonography can find calcifications or hypoechoic areas in
the lateral epicondyle region and may be useful in diagnosing
tendonosis.
In cases of chronic lateral epicondylitis, the capsule below the
extensor carpi radial brevis (ECRB) tendon should be examined for
tears.
Currently, the best modality for diagnosing capsular tears is
arthroscopic techniques. Although MR falls short of accurately
imaging capsular tears of the ECRB tendon, CT arthrography has
shown excellent success at displaying capsular tears.
Medial Epicondylitis
Known to patients as golfer’s elbow, medial epicondylitis is common
in individuals who overuse their wrist flexors and forearm pronator
but is seen far less frequently than lateral epicondylitis.
Medial epicondylitis primarily affects the insertion point of the flexor
carpi radialis. The patient presents with pain at the medial aspect of
the elbow.
As with lateral epicondylitis, radiographic evidence of medial
epicondylitis can be difficult to find, but small calcifications or spurs
next to the medial epicondyle are common. MR imaging most often is
used for diagnosis.
Arthritis
Arthritis is a joint disorder that results in inflammation of the joints
within the body. There are varying kinds of arthritis, each exhibiting
different causes and symptoms. Regardless of the type of elbow
arthritis, the initial stages of pain management include pain
medication and physical therapy. Occasionally, corticosteroid
injections are used for pain management, but physicians must use
caution to ensure that the injections do not lead patients into a false
sense of treatment and overuse of the elbow joint, causing further
deterioration.
Rheumatoid Arthritis
Rheumatoid arthritis is a severe form of arthritis that progressively
affects the body’s joint tissues. Joint erosion and destruction are
common because of the severity of rheumatoid arthritis.
Rheumatoid arthritis commonly begins in the radiocapitellar joint.
The radial head may move out of its regular position and cause
problems with other elbow anatomy.
Radiographs can monitor structural changes caused by rheumatoid
arthritis, but radiography is not the preferred method for early
disease assessment. Bone erosion from rheumatoid arthritis is better
displayed on CT images than on MR images or radiographs.
Ultrasonography can show inflammation related to rheumatoid
arthritis and document destructive changes.
Osteoarthritis
Arthritic conditions of the elbow are not uncommon, but
osteoarthritis of the elbow is rare. Osteoarthritis is much more
prevalent in weight-bearing joints, such as knees and hips, and in the
interphalangeal joints of the hand.
Patients with osteoarthritis affecting the elbow experience the most
pain during terminal flexion and extension of the joint.
Radiographic evidence of osteoarthritis includes osteophyte
formation. These osteophytes usually are near the ulnohumeral joint
and occasionally impinge on the ulnar nerve. MR and CT images of
the elbow help show the joint surfaces and detect loose bodies or
spurs.
Gout
Elevated uric acid levels can result in monosodium urate crystals to
infiltrate the synovial fluid of joint spaces and lead to gout. Gout
usually is found in the joint spaces of the toes but can appear at the
elbow.
Evidence of gout is obvious in patients with advanced disease but is
not often apparent on images of early cases. MR images are better for
evaluating synovial involvement, and CT is better for displaying
intraosseous lesions. Ultrasonography also can highlight thickening of
the synovial fluid, along with inflammation.
Overuse Conditions in Children
Children also can have elbow injuries and conditions related to
overuse of the elbow joint. Examples of these problems, sometimes
referred to as Little League elbow, include traction apophysitis of the
medial epicondyle, Panner disease, and osteochondritis dissecans.
Traction Apophysitis of the Medial
Epicondyle
Traction apophysitis of the medial epicondyle is inflammation of the
medial epicondyle due to an avulsion tear or trauma. Because of the
timing of ossification in children, traction apophysitis is the most
common elbow injury in young children.
Approximately 97% of elbow problems in baseball pitchers are
associated with symptoms of the medial elbow. The main symptom of
apophysitis of the medial epicondyle is pain immediately after a
repetitive motion such as throwing.
Radiographs of the elbow might show slight widening of the
apophysis, but this can be missed easily if the radiologist does not
review comparison radiographs of the opposite elbow. MR imaging
can show edema of the bone marrow around the medial epicondylar
area.
Panner Disease
Osteochondrosis affects the ossification centers of children when the
bone degenerates and then begins to regenerate, producing excessive
calcification in some areas. Panner disease is a form of
osteochondrosis that affects the capitulum of the elbow.
Panner disease is most common in preadolescent boys and children
younger than 10. Panner disease is the most common reason for
lateral elbow pain in young children and routinely affects the
dominant arm.
Radiographs can display sclerosis and areas of decreased density at
the capitulum. An MR series with T1-weighted images might show
fragmentation with decreased signal intensity at the capitulum
surface.
Osteochondritis Dissecans
A more advanced form of osteochondrosis is osteochondritis
dissecans. These lesions result from death of the articular cartilage or
subchondral bone of the capitulum due to a lack of blood supply.
Subchondral bone provides cartilage support at articulation sites. If
the subchondral bone or cartilage is slightly fractured, it is known as
osteochondritis dissecans.
Patients with these osteochondritis dissecans lesions often have plica,
an inflamed lining of the radiocapitellar joint. Because the pain is
located on the lateral side of the elbow, radiocapitellar plica
commonly is misdiagnosed as lateral epicondylitis.
Osteochondritis Dissecans
Osteochondritis dissecans typically affects adolescent athletes aged
11 to 21 years.
Osteochondritis dissecans is characterized by a dull ache with no
centralized location. The pain may disappear when the child is resting
then reappear during strenuous activities. If fragments are loose in
the area, the joint may routinely catch or cause a popping sensation.
Osteochondritis Dissecans
Radiographs typically are not very sensitive for identifying loose
bodies, and less than 30% of positive loose bodies are found using
radiography.
CT of the elbow joint can help physicians locate and count loose
bodies found throughout the elbow compartments before the patient
undergoes arthroscopic procedures to remove the fragments.
On MR images, osteochondral lesions can be confused with normal
osseous variants of the elbow.
Ultrasonographic imaging of osteochondritis dissecans is rare.
Arthroscopy is used most often because it remains a safe and
effective way to diagnose and evaluate osteochondritis dissecans or
lesions of the elbow. The benefit of arthroscopy is the ability to
immediately remove any loose bodies or deliver other treatments.
Nerve Damage
The most common nerve condition in the elbow is ulnar neuritis. This
inflammation of the nerve can cause radiating pain from the posterior
medial elbow to the hand and fingers. Compression of the elbow
nerves is attributed to a wide range of abnormalities.
An ulnar nerve injury typically is associated with supracondylar
fractures when the arm is in hyperflexion, but most ulnar nerve
injuries occur because of direct blows to the nerve. Damage to the
ulnar nerve can lead to numbness and tingling of the hand.
In severe cases of ulnar nerve injury, symptoms can last for years after
the trauma. This is commonly known as tardy ulnar palsy.
MR imaging is the best modality to show nerve damage and edema.
Elbow Injuries: Ligament or Tendon
Injury
About 50% of the medial and lateral plane of the elbow is stabilized
by ligaments. If the anterior bundle of the elbow’s MCL is injured, the
elbow becomes extremely unstable except when fully extended.
Radiography can assess ligament tears and joint stability, particularly
with valgus or varus stress applied during a fluoroscopic examination.
Gadolinium contrast often is used during MR imaging to help enhance
MCL injuries. Although MR imaging is highly sensitive for complete
tears of the MCL, it is not the method of choice for viewing partial
tears. CT arthrography has a higher rate of identifying partial tears. In
either modality, a sagittal projection is the best choice for
determining the size of a ligament injury.
Dislocations
The elbow is the joint that is dislocated most often among pediatric
patients. It is the second most dislocated joint in adult patients, with
50% of cases resulting from sports activities.
Elbow dislocations can occur as a result of many situations but most
often arise from a fall on an outstretched hand. The most common
dislocation involves displacement of both the ulna and radius.
Elbow dislocations often present with other injuries. The MCL is
routinely compromised in elbow dislocation. With MCL damage, the
elbow joint might remain unstable unless the ligament heals or is
surgically repaired.
A patient with an elbow dislocation most often experiences extreme
pain and swelling. A deformity may or may not be clearly seen.
Dislocations
An AP and lateral radiograph elbow series is sufficient to diagnose an
elbow dislocation.
An elbow reduction most often is completed by having the patient’s
upper arm held in place while applying a steady pull on the forearm
and hand. Once the dislocation is reduced, the elbow should be
tested for mobility and examined with radiography to ensure
satisfactory reduction of the joint and exclude any further bone
injury.
A neurovascular examination should be performed and results noted
before and after reducing the elbow joint dislocation. Following an
elbow dislocation, extension may become compromised and the
elbow may be unstable. Over time, some patients might develop
arthritis or ectopic bone.
Heterotopic Bone Formation
Formation of bone or calcification that is not in the normal bone
growth area is called heterotopic bone formation. Heterotopic bone
growth at the elbow can be associated with traumatic injury of the
elbow, but heterotopic bone formation of the elbow also can be
caused by central nervous system trauma or excessive burns.
The formation of juxta-articular bone at the elbow joint can cause
problems because of decreased full range of motion. Once elbow
motion has been compromised by heterotopic bone formation, the
only treatment for restoring motion is surgical resection of the bone.
Fractures
The proximity of nerves, arteries, tendons, muscle, and bones in the
elbow contributes to the elbow being considered one of the most
complex fracture sites. Clinical examination begins by observing the
patient’s arm. When both arms hang normally at the patient’s sides,
there should be a 5° to 15°separation of the forearms and hands
from the body. This arm-to-body separation is known as “the carrying
angle.” If the patient’s arms and hands are not observed within the
acceptable ranges, it could indicate an elbow fracture. Any variation of
the angle that is more than 15°is known as cubitus valgus. Angles less
than 5°are called cubitus varus.
All fractures are serious and should be treated as such, although open
fractures are at higher risk for adverse complications.
There are three distinct phases in the healing process of bones and
complete fracture healing can last for months or years.
Distal Humerus Fractures
Distal humerus fractures represent only 2% of adult fractures. These
fractures can appear in both condyles and often continue into the
joint space.
Location determines the classification of distal humerus fractures.
Patients with distal humerus fractures experience extensive swelling,
deformities, and pain. These fractures also can produce bruising of
the skin. Flexion of the arm may produce crackling or popping sounds
from bone fragments.
Distal Humerus Fractures
A 2-projection radiographic examination usually is sufficient to evaluate
distal humerus fractures. A lateral oblique projection is helpful for
diagnosing lateral condyle fractures or displacement. An oblique
radiograph of the elbow might help identify nondisplaced fractures of
the condyle in children.
Posterior displacement of the humerus, often seen in fractures, affects
the orientation of the anterior humeral line seen on the lateral image. If
the anterior humeral line passes through the anterior portion of the
capitulum or does not meet the capitulum at all, a fracture is possible.
Displaced fractures are generally stabilized with surgery. Splinting is
sufficient in nondisplaced fractures. It is important to retake radiographs
of the elbow after several days of splinting to ensure adequate
positioning.
Olecranon Process Fracture
The olecranon process is at high risk for fracture because of its
prominent position directly under the surface of the skin. Olecranon
process fractures generally occur when an individual falls directly
onto the flexed elbow, resulting in a comminuted fracture. Other
fractures of the olecranon process include avulsion, nondisplaced
transverse and nondisplaced oblique fractures, and fracturedislocations. Swelling and extensive bruising often are noted
following an olecranon process fracture.
AP and lateral radiographs can usually demontrate olecranon process
fractures, with a lateral projection providing the best view of the
fracture.
Olecranon Process Fracture
If an olecranon process fracture is nondisplaced, a posterior splint to
flex the elbow 90°usually is the first step in treatment. Follow-up for
this treatment includes radiography to ensure that the fracture
remains nondisplaced. Displaced fractures require internal fixation
with plates, screws, pins, or wires to align the bone properly.
Even after healing, an olecranon process fracture can produce loss of
motion regardless of treatment. If fixating hardware is used, the
hardware can irritate the tissues around the fracture site, causing
more pain.
Coronoid Process Fracture
Fractures of the coronoid process typically occur in conjunction with
posterior elbow dislocations. An avulsion fracture of the coronoid is
possible if the brachialis muscle is subjected to forceful contraction.
Antecubital fossa tenderness and swelling are common symptoms of
coronoid fracture.
The radial head or oblique projection of the elbow highlights possible
fractures of the coronoid. The lateral projection best demonstrates
coronoid fractures, however, and also highlights avulsion fractures.
Radial Head Fracture
The radial head is believed to be the secondary stabilizing source for
the elbow during valgus stress. As a result, radial head fractures tend
to occur when patients fall with a forearm turned inward and land on
an outstretched hand. These are the most common elbow fracture
among adults.
Patients who have radial head fractures experience pain on the outer
surface of the elbow and may not be able to pronate or supinate the
forearm. The elbow can show signs of swelling, limiting the amount of
flexion and extension.
Standard 2-projection radiographs of the elbow are routine for
suspected radial head fractures because these fractures usually
produce a positive posterior fat pad sign on radiographs.
Capitulum Fractures
Fractures of the capitulum are not very common, but when they occur,
they share a similar mechanism of fracture as radial head fractures
because of the axial alignment of the capitulum. In fact, nearly 50% of
capitulum fractures are accompanied by a radial head fracture.
Results of routine radiography often are misleading in cases of capitulum
fracture. The AP projection can hide a fracture fragment behind the
humerus, and any rotation or a slight oblique lateral positioning often
obscures a capitulum fracture. Radiographs of the elbow consistently
show a positive fat pad sign on the lateral projection, but radiographers
should acquire a radiocapitellar projection to better demonstrate any
fracture fragments. Determining the degree of displacement in
capitulum fractures is difficult with radiographs. CT images can show
precise details of the fracture.
Avulsion Fracture
Stress to the elbow joint can cause avulsion fractures. Avulsion
fractures often are found in adolescents aged 9 to 12 years, and they
are the most common type of elbow fracture in adolescent athletes
who participate in throwing as part of their sport.
Avulsion fractures most often are found before the secondary
ossification centers fuse. A common symptom of avulsion fractures is
an acute popping sensation in the elbow followed by pain. The pain
often is felt immediately after making a hard pitch or throw.
Images obtained following the injury might show a disconnection of
the medial epicondyle apophysis or subtle displaced fractures.
Occasionally, a gravity stress test or manual stress projections of the
elbow also are ordered.
Combined Fractures and Dislocations
Monteggia fracture-dislocations involve a fracture of the ulnar shaft
and displacement of the radial head. If the alignment of the
radiocapitellar line does not point to the capitulum on all radiographic
projections, a Monteggia fracture or lateral condyle fracture is likely.
Galeazzi fracture-dislocations combine a distal radial head disruption
with a distal radial fracture. Essex-Lopresti fracture-dislocation
consists of a radial head fracture that is comminuted and a distal
subluxation or dislocation of the radioulnar joint.
The “terrible triad” is a devastating elbow injury that includes a radial
head fracture, an MCL injury, and a coronoid process fracture.
Arterial Injuries
Specific trauma, such as supracondylar fractures, carry such a high
risk for arterial injury that arterial injury should be suspected in most
cases. Arterial injuries are very serious and can lead to contracture or
loss of the affected limb.
If the brachial artery is damaged, the patient may have a decreased
pulse, radiating pain, decreased skin temperature, and the skin of the
affected arm may appear pale. A pulse should be detectable distal to
the fracture. If the skin appears pale or the pulse is noticeably low or
absent, arterial injury is likely. A CT examination with IV contrast can
display any occlusions or hematomas.
Fractures in Children
Fractures of the elbow are not uncommon in children, given their
typical behavior. Supracondylar fractures are the most common
elbow fracture in the pediatric population, however, constituting up
to 60% of cases. After the reduction of a supracondylar fracture, a
radiographic image using the Jones method image can confirm
adequate reduction.
Roughly 35% of pediatric skeletal injuries involve a growth plate.
During the growth process, the long bones of pediatric patients
contain a physis or growth plate that allows the bone to grow
longitudinally. The bone in the growth plate grows rapidly. This can
benefit fracture healing, but care must be taken when managing any
fracture that extends into the growth plate because the bone can heal
unevenly, leading to deformities.
Fractures in Children
If a posterior fat pad is seen on a lateral radiograph and no other
abnormality is seen, it is likely that the patient has a nondisplaced
intracapsular fracture. About 76% of follow-up radiographs of pediatric
patients show healing fractures in the elbow area. These findings
support the decision to manage these situations as though a fracture
existed in the original radiograph. If a hairline or small fracture is
suspected after a negative radiographic examination, pediatric patients
can return sooner than adult patients for repeat images because
children have faster callus formation.
Radiologic technologists and care providers should be aware of specific
elbow fractures that might indicate child abuse. A transphyseal fracture
of the humerus, common in children younger than 6 years, often
indicates child abuse. This fracture normally presents as pain in the
elbow, limited range of motion, and swelling over the fracture site.
Fractures in Children
The routine 3-projection radiograph of the elbow is not always helpful
to diagnose a transphyseal fracture because of a lack of ossification in
pediatric patients. Comparison radiographs of the opposite elbow can
assist the radiologist in diagnosing transphyseal fractures. If
radiographs of the elbow are not definitive, MR imaging,
ultrasonography, or arthrography may be required to confirm a
diagnosis.
If a transphyseal fracture is found and child abuse is suspected, the
provider might want to order additional radiographs. Child abuse
victims often have fractures in multiple areas of their bodies. The
types of child abuse fractures that might be seen in addition to the
transphyseal fracture are diaphyseal or long-bone shaft fractures.
Congenital Radial-Ulnar Synostosis
Bones sometimes can fail to form as they should in children. In
congenital radial-ulnar synostosis, the radius and ulna fail to grow
apart at their proximal locations. This condition can be bilateral or
unilateral. When the proximal radius and ulna are not freely mobile,
supination and pronation of the forearm is limited.
Radiographs of the forearm confirm cross-synostosis of the proximal
radius and ulna. This appearance of the bony union is easily seen by
the increased bony formation.
Radial Head Subluxation
Children who have loose ligaments are at risk for subluxation of the
radial head. Radial head subluxation sometimes is called nursemaid’s
elbow and is the most common elbow injury in younger children. Most
often, radial head subluxation affects the left arm of children who are
between the ages of 2 and 3 years.
Problems with the radial head develop when a young child’s arm is
pulled with forearm extension and pronation. This injury often occurs
when a child is pulled up by the arm or suddenly drops to the floor to
tug away from being held.
Diagnosis of radial head subluxation is complicated by young children’s
inability to describe their symptoms in detail. Radiographs of the elbow
do not always show a subluxation of the radial head. Occasionally, a
displacement of the radiocapitellar line is evident, but the lack of this
displacement on images should not alter treatment plans.
Conclusion
Elbow disorders and injuries can be painful and problematic for
patients and complex for the medical professionals providing imaging
and care. Understanding the anatomy of the elbow and medical
diagnostic imaging methods to best demonstrate elbow injuries and
disorders helps radiologic technologists enhance the diagnostic
process and directly benefits patient care.
Discussion Questions
Explain the radiologic modality choices for diagnosing
elbow disorders and injuries.
Discuss the most common elbow disorders and injuries.
Discuss some of the differences between pediatric and
adult elbow anatomy as well as different elbow
disorders and injuries specific to children and adults.
Additional Resources
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and resources that will be valuable in your
radiologic technology education.