Olecranon fractures are a diverse group of injuries, ranging from simple nondisplaced fractures to complex fracture-dislocations of the elbow joint.  The human's unique prehensile skill largely depends on the integrity of the bones, ligaments, and muscles around the elbow joint. The elbow not only bends the arm but also permits pronation and supination of the hand. Fractures of the olecranon are common and are usually detected easily but require careful treatment for an optimal result. [2, 3, 4]
Olecranon fractures can be complex injuries, presenting the physician with a wide array of surgical and nonsurgical therapeutic options. A successful functional outcome after olecranon fractures correlates directly with accuracy of anatomic joint reduction, restoration of mechanical stability that allows early motion, respect for the soft tissues, and maintenance of an intact extensor mechanism.
For patient education resources, see Broken Elbow.
The elbow is a complex hinge joint. The major stabilizers to valgus stress (ie, bending away from the body) are the medial (ulnar) collateral ligament and the radial head. The major stabilizer to varus stress (ie, toward the body) is the lateral collateral ligament complex. The coronoid process stabilizes the humerus against the distal ulna.
The olecranon (the proximal bony projection of the ulna at the elbow; see the image below) also prevents anterior translation of the ulna with respect to the distal humerus. The anterior surface of the olecranon is covered with articular cartilage. Therefore, all fractures (except the rare tip fractures) are intra-articular fractures. The olecranon articulates with the trochlea of the humerus. The triceps inserts into the posterior third of the olecranon and proximal ulna. The periosteum of the olecranon blends with the triceps.
The ulnar nerve lies on the posterior aspect of the elbow, posterior to the medial collateral ligament. The ulnar nerve sweeps anteriorly to join the ulnar artery. The ulnar neurovascular bundle may be at risk during Kirschner wire (K-wire) fixation.
Fracture displacement is largely due to the pull of the triceps, which tends to pull a separated fragment upward but is resisted by the strong fibrous covering on the olecranon. This fibrous covering is formed by the blending of fibers in the lateral ligaments, the elbow capsule, and some triceps fibers that blend with the periosteum. If the fracture force does not tear the fibrous sheath, little or no tendency toward displacement exists, even in the presence of comminution. Usually, wide separation of fragments indicates an extensive tearing of the fibrous sheath in which the unopposed triceps is contracted, drawing the separated fragment upward.
The most common mechanism of an olecranon fracture is a fall on the semiflexed supinated forearm. As the hand strikes the ground, muscles are tensed to break the fall, and the powerful triceps snaps the olecranon over the lower end of the humerus, which acts as a fulcrum. The next most frequent cause of this injury is direct trauma, as in falls on, or blows to, the point of the elbow.
Occasionally, the olecranon may be fractured by hyperextension injuries, such as those resulting in elbow dislocation in adults or supracondylar fractures in children. Very rarely is the olecranon broken by muscular violence, as in throwing. Stress fractures can occur in baseball players and other throwing athletes.
Even though the olecranon is a very heavy, strong process of bone, it is fractured frequently in adults. This is partly because of its exposed position on the point of the elbow, where most direct injuries to the elbow occur, and partly because of the tremendous cross-strain put on the olecranon during falls on the flexed forearm.
The olecranon process is rarely broken in children, because in early life, it is short, thick, and relatively much stronger than the lower end of the humerus. Usually, children sustain supracondylar fractures of the humerus instead. Nevertheless, the clinician should have a high index of suspicion in children because olecranon fractures do occur, often associated with radial head subluxation or dislocation; failure to diagnose the fracture can have long-term negative consequences.
Open fractures occur in 2-31% of cases. Neurologic injuries to median, radial, or ulnar nerves may occasionally occur. Ulnar neurapraxia has been reported in 2-5% of cases. Generally, symptoms resolve with conservative treatment, but late neurolysis or transposition may occasionally be required.
Approximately 95% of patients with olecranon fractures are expected to have near-normal function; 20-25% of patients will develop radiographic evidence of arthrosis at 15- to 20-year follow-up, but these patients are usually asymptomatic.
Age is the most important factor influencing outcome: Younger patients generally do better than older ones. 
One study retrospectively reviewed the outcome of 18 patients who underwent locking-plate osteosynthesis after open reduction for comminuted olecranon fractures.  The study results found that in all cases, complete union was achieved. The data conclude that while the risk of limited elbow motion is high in cases with concomitant injuries, locking plates are an additional and often successful option for olecranon fracture fixation.
Buijze et al compared the stiffness and strength of contoured locking compression plate fixation (combined with an intramedullary screw) to one-third tubular plate fixation (combined with bicortical screws) in a cadaveric comminuted olecranon fracture model with a standardized osteotomy.  Stiffness was measured by subjecting the specimens to cyclic loading while measuring gapping at the osteotomy site, and strength was measured by subjecting specimens to ramp load until failure. The authors found no significant difference in contruct stiffness and strength between the two fixation methods, and all failures consisted of failure of the bone, not of hardware.
In a study by Buijze and Kloen, 19 patients with an acute comminuted olecranon fracture were managed with a contoured locking compression plate and intramedullary screw fixation, 16 of whom were available for follow-up at a minimum of 12 months after fixation.  The authors noted that in patients managed with plate fixation for olecranon fractures, placement of an axial intramedullary screw may obstruct the placement of bicortical screws in the ulnar shaft. As a solution, they assessed the effectiveness of unicortical screws with a contoured locking compression plate.
In this study, all 19 fractures healed, and the mean time to fracture union was 4 months.  The mean Disabilities of the Arm, Shoulder and Hand score was 13. According to the Mayo Elbow Performance Index and the Broberg and Morrey grading system, 15 of the 16 patients followed had a good or excellent outcome. In 9 patients, hardware removal was necessary; after removal, the mean elbow extension deficit improved from 34º to 10º, and the mean flexion improved from 118º to 138º.
According to Iannuzzi and Dahners, in comminuted fractures of the olecranon (Mayo type IIB), it may be difficult or even impossible to preserve the olecranon's normal articulation with the trochlea of the humerus.  The authors therefore described a modified technique for reconstructing these fractures when it is not possible to achieve a stable anatomic reduction and fixation; in this technique, the comminuted fragments are excised and the proximal olecranon fragment is advanced past the resulting defect and fixed to the distal ulna. The authors presented two cases with clinical follow-up and note that satisfactory preservation of range of motion and elbow stability were achieved in each case.