1 Description
The olecranon is a bony prominence of the ulna that represents that
bone’s most proximal posterior surface at the elbow. While the medial
border of the olecranon is a part of the flexor carpi ulnaris origin and
the lateral border is an attachment point for the anconeus muscle, the
major muscle attachment is that of the triceps. The olecranon can thus
be fractured (avulsed) by a traction force from triceps contracture. The
subcutaneous position of the olecranon renders it susceptible to direct
trauma as well. Displaced fractures of the olecranon often disrupt the
articular surface of the elbow joint; these have to be realigned with
surgery. Further, because the triceps can displace fractures that were
originally not displaced, and because the elbow is relatively intolerant
of prolonged immobilization, surgical treatment rather than casting is
often needed even for fractures with minimal displacement.
Figures: radiograph of displaced fracture
2 Structure and
function
The olecranon is a strong process of the proximal and posterior ulna
that, together with the coronoid process, forms the trochlear notch.
This notch holds the trochlea of the distal humerus forming the
ulnohumeral articulation, the hinge joint of the elbow.
The trochlear notch is covered with articular cartilage, therefore most
olecranon fractures (except the ones occurring exclusively on the tip)
are, by definition, intra-articular fractures.
Successful treatment of olecranon fractures requires not only reestablishment of the extensor mechanism (which would be disrupted
if/when a fracture displaces) but preservation of elbow stability.
The main side-to-side (valgus and varus) stabilizers of the elbow are
the collateral ligaments and the ulnohumeral/radiohumeral articulation,
which provide a buttress against compressive forces laterally. The
olecranon is an important stabilizer too: it blocks anterior translation of
the ulna with respect to the distal humerus just as the coronoid
process of the ulna resists posterior subluxation of the ulna.
The triceps muscle inserts into the proximal ulna and posterior third of
the olecranon. Its fibers blend with the periostium of the olecranon, the
lateral ligaments and the articular capsule, forming a strong fibrous
covering. This fibrous covering prevents fractures from being
dramatically displaced unless the force is so great that the soft tissues
rupture along with fracture of the bone.
The lateral border of the olecranon is an attachment point for the
anconeus muscle.
The ulnar nerve runs on the posterior aspect of the elbow, behind the
medial epicondyle of the humerus; it then turns anterior joining the
ulnar artery. Its proximity to the olecranon makes it vulnerable to injury
when fractures occur.
The medial border of the olecranon is a part of the flexor carpi ulnaris
origin.
3 Patient presentation
Patients with fractures of the olecranon present with elbow pain after
direct elbow trauma or a fall. The clinical examination can detect
varus/valgus instability, but the primary determination is whether the
extensor mechanism is intact.
The mechanism of injury often determines the fracture pattern. If there
is a fall on a semi-flexed arm, when the hand strikes the ground, the
triceps muscle forcefully contracts, resisting further flexion of the
elbow. This “breaking the fall” reaction leads to breaking the bone: an
avulsion fracture of the tip of the olecranon, pulled off by the triceps.
This mechanism is more commonly seen in elderly patients.
Less frequently, the cause is direct trauma to the tip of the elbow,
which usually leads to comminuted fractures. This is mostly the
mechanism in younger patients.
In elderly patients, the bone fracture is often an isolated finding. The
diagnostic attention is paid to determine why the patient fell. In
younger patients, the mechanism of injury is often of higher energy
and diagnostic attention is paid to make sure that there are no
associated injuries elsewhere.
Other less common mechanisms are hyperextension injuries, such as
those resulting in elbow dislocation in adults or supracondylar
fractures in children. These can fracture the olecranon when it is
impacted against the olecranon fossa of the distal humerus. Stress
fractures due to muscle forces such as throwing are a rare cause of
olecranon fractures in adults, however in young pitchers it is relatively
common.
Because most fractures of the olecranon involve the joint surface,
there is generally hemorrhage into the joint with a resultant effusion.
This produces pain and swelling. Skin openings are somewhat
common given the subcutaneous location of the ulna. Ulnar nerve
neurapraxia may develop in 2-5% of cases.
4 Clinical evidence
A standard lateral radiograph of the elbow is sufficient for evaluation of
isolated olecranon fractures. A true lateral X-ray is of paramount
importance because it helps to determine the extent of the fracture,
degree of displacement, comminution, radial head subluxation, and
the degree of articular surface involvement.
A non-displaced, transverse, or slightly oblique intra-articular break
near the base of the olecranon is the most commonly seen olecranon
fracture.
Figures: radiograph of nondisplaced fracture
If there is absence of radiographical evidence of a fracture, an
important sign to look for on the lateral X-ray is the fat pad sign. This
is a sign of intra-articular effusion; distension of the joint capsule
elevates the fat pads on top of it, suggesting an intra-articular fracture.
Figures: radiograph of fat pad (same as radial head)
It is important to assess for fracture displacement potential on
radiographs. That is, most olecranon fractures exhibit little or no
displacement, but some may displace with elbow motion. Thus, a
fracture is considered non-displaced only when the fracture gap is less
than 2mm even when the elbow is flexed at 90°.
Joint stability can also be inferred from radiographs. If the fracture
involves more than 50% of the ulnohumeral articulation, the elbow can
be assumed to be unstable. Associated lesions such as coronoid
fractures, radial head fractures or torn collateral ligaments may also
produce instability.
5 Epidemiology
Olecranon fractures account for 10% of elbow fractures in adults. In
children, by contrast, with excessive forces on the elbow, the distal
humerus is more likely to be broken. This is because the olecranon is
comparatively shorter and thick before skeletal maturity. This point is
noteworthy because the presence of an olecranon fracture in a child
suggests a primary bone disease such as osteogenesis imperfecta.
6 Differential
diagnosis
Anterior elbow dislocations often occur with associated olecranon
fractures, especially when a posterior direct blow is suffered. Lateral
radiographs confirm this association. Similarly, Monteggia fractures (ie
a fracture of the proximal third of the ulna with dislocation of the head
of the radius) can be produced by the same mechanism as an
olecranon fracture; this would be detected with adequate radiographs.
Supracondylar fractures of the humerus should also be considered,
especially in children who fall on semiflexed arms and/or suffer direct
blows on the elbow. Radial head fractures and fractures of the
coronoid process may produce elbow instability and complicate
olecranon fractures.
An abnormality in the relationship between the osseous landmarks
(i.e. line and triangle formed by epicondyles and olecranon) may be
used to distinguish between intra-articular fractures, dislocations and
supracondylar fractures.
7 Red Flags
Comminution of an olecranon fracture suggests higher energy and
implies other associated injuries (which must be diligently excluded)
Blood on the skin may signify an open fracture, perhaps sustained by
the bone poking out when the fracture is maximally displaced, then
retracting back into the skin when the bone straightens out somewhat.
Inadequate imaging. Even if the presentation is classic for an isolated
elbow injury, films of the wrist are required.
8 Treatment options
and
outcomes
The treatment goals are to maintain a stable and anatomic reduction,
achieve stability of the joint, and enable early active motion .
Fractures with up to 2mm of displacement with intact extensor
mechanisms may be treated with three to four weeks of casting in a
long arm cast. The elbow can be placed between 45° and 90° of
flexion. After one month, supervised passive motion is started until
radiographic evidence of union is achieved, then active movement is
encouraged.
Fractures with significant displacement (>2mm) or comminution may
require surgical intervention because of compromise of the extensor
power. Approximately 70% of the extensor power is estimated to be
lost when the fracture is displaced more than 1.5 cm.
FIGURES: EYE CANDY SHOWING Rx
FIGURE Tension band wiring: A tension band wire is the most
common fixation technique for simple displaced fractures without
comminution, especially avulsion type fractures. It uses Kirchner wires
and tension wires and works by compressing the fracture surfaces
together.
FIGURE Intramedullary screw fixation: Intramedullary screw fixation is
the most secure technique. Biomechanically, screw fixation does not
provide as secure a fixation as tension-band wiring. However, by
adding a tension band, excellent fixation can be obtained.
FIGURE Plate fixation: Plate fixation is recommended for extensive
comminuted or unstable oblique fractures and also when associated
injuries are present (e.g. coronoid fractures).
Excision of the fracture fragment and reattachment of the triceps
tendon may be indicated in elderly patients with osteoporotic bone and
in low-demand patients, especially when the fragment is too small or
comminuted for successful internal fixation.
Olecranon fractures heal well in most instances and recovery of
normal function is achieved in more than 95% of patients. Functional
outcome is dependent on fracture severity, length of immobilization,
and patient factors. The best outcomes are observed in patients who
have minimally displaced fractures treated non-operatively.
In patients treated operatively, symptomatic hardware requiring
removal is the most frequent complication. Injury to the ulnar artery,
the median or anterior interosseus nerves (AIN) is possible with
penetration of the K-wires through the anterior cortex of the ulna.
Infection following operative treatment happens rarely. Heterotopic
ossification occurs in 10-15% of patients. Loss of motion is rarely
significant (less than 15° of extension) and nonunion occurs in about
1% of patients and is treated by internal fixation and bone grafting .
9 Risk factors and
prevention
Risk factors include any underlying medical pathology that could
cause a fall (e.g. syncope), especially in older patients. Also, any
pathology that could weaken the bone like osteogenesis imperfecta in
children or those that cause osteopenia such as osteoporosis, steroid
use, or vitamin D deficiency. Type of physical activity becomes a risk
factor only in young pitchers who are prone to stress fractures.
Elbow pads for high contact sports and activities may be used to
protect from direct blows that could cause fractures.
10 Miscellany
In mixed martial arts competitions, an elbow drop (a move in which a
fighter drives his elbow into the opponent's body) takes advantage of
the strength of the olecranon. It is forbidden primarily because of the
risk to the recipient of the blow, though of course the striker may
sustain a fracture too.
Olecranon is a word of Greek origin whose second root is “kranion”,
meaning head. (The word “cranium” has the same root.) Still, the
olecranon should not be thought of as the “ulnar head” as the first root
is “olene”, meaning “elbow”.
11 Key terms
olecranon; ulna; ulnar nerve neurapraxia; triceps advancement;
tension band wiring; bipartite olecranon; patella cubiti.
12 Skills
Recognize on examination failure of the extensor mechanism, fracture
displacement and joint instability; correctly interpret radiographs and
describe fracture pattern; identify fractures that would require
operative treatment; apply elbow immobilization until definitive
treatment is obtained.