The olecranon is the most proximal part of the ulna, easily palpated under the skin at the elbow. As a result, the olecranon is vulnerable to fractures, usually from a direct blow after a fall. Fracture of the olecranon accounts for approximately 10% of upper extremity fractures in adults. Typically, olecranon fractures are isolated injuries. However, many olecranon fractures are displaced and result in disruption of the extensor mechanism of the elbow. Those that are not initially displaced are nonetheless still at risk of displacement by the pull of the triceps. Therefore, surgical treatment is often required.
Structure and Function
The olecranon is the proximal-most part of the ulna (see Figure 1). The coronoid process anteriorly and the olecranon posteriorly together define the trochlear notch in which the distal humerus sits. The olecranon provides attachment for the triceps tendon.
There are key structure/function points to recall:
- An olecranon fracture is an intra-articular fracture. Its anterior surface and the coronoid process forms the hinge joint with the trochlea of the distal humerus.
- The triceps tendon inserts on the posterior third of the olecranon which provides a lever arm for extension of the elbow. Thus, a fractured olecranon is subject to displacement by the pull of the triceps.
- The ulnar nerve is adjacent to the olecranon, so this nerve needs to be assessed when the olecranon is injured and must be protected when the injury is treated.
- The olecranon is subcutaneous with only a thin layer of soft tissue and skin overlying it Thus, a “closed” olecranon fracture can easily become an “open” one (i.e., breaking through the skin). Also, there are risks of impaired post-operative wound healing and pressure damage from immobilizing devices such as casts and splints.
The mechanism of injury is either a direct blow to the elbow or a fall onto an outstretched upper extremity. (In the case of a fall, the pull of the triceps can avulse a piece of the ulna).
Olecranon fractures are typically a result of high energy trauma in young individuals and a low energy fall in older individuals.
Olecranon fractures typically present as isolated injuries, though they also can be part of a more complex elbow injury (i.e., including the humerus, radius and nearby soft tissues).
Displaced olecranon fractures can create a palpable defect between the fracture ends, though there is often a lack of deformity.
In cases of polytrauma, patients should be closely evaluated for associated injuries. The subcutaneous location of the olecranon makes open fractures more likely. A careful skin exam is therefore essential.
Radiographs in the anteroposterior (AP) and lateral plane should be obtained. Emphasis should be placed on ensuring the lateral view is a true lateral view and that the AP clearly shows the proximal radius and ulna in relationship to the humerus.
A direct blow usually results in a comminuted fracture, whereas a fall is associated with a transverse fracture line.
The fracture is usually displaced, owing to the pull of the triceps (see Figure 2).
Olecranon fractures account for about 10% of upper extremity fractures. The majority of fractures occur in individuals 50 years and older as a result of a fall from standing height. Until proven otherwise, olecranon fractures should therefore be considered to be fragility fractures (prompting an investigation of metabolic bone disease). In younger individuals, a higher energy mechanism of injury is more common.
Olecranon fractures are commonly associated with coronoid fractures, collateral ligament injuries, radial head and neck fractures, and radial head dislocations.
In children, an olecranon fracture is commonly associated with a Monteggia fracture. This eponym refers to a fracture of the proximal third of the ulna fracture combined with radial head dislocation or instability.
If the coronoid process is also fractured, the humero-ulnar joint can be destabilized.
Obtaining a true lateral radiograph is essential to evaluate the fracture.
Comminution of an olecranon fracture is more likely in a high energy mechanism of injury. In such cases the patient should be examined for other associated injuries.
The superficial position of the olecranon increases its susceptibility to an open fracture. A thorough skin exam is therefore essential.
As with all fractures near vital structures, careful initial neurovascular evaluation and documentation is important as a baseline for subsequent monitoring prior to, and post manipulation, splintage or surgery.
Olecranon fractures may be sign of fragility – weak bones or a propensity to fall or both – and thus the presence of the injury itself may be a red flag for these conditions.
Treatment Options and Outcomes
Nondisplaced fractures with an intact elbow extensor mechanism can be treated non-operatively but these injuries must be closely monitored with radiographs to ensure that they do not displace.
If non-operative treatment is chosen, the elbow is immobilized between 45 to 90 degrees of flexion for 3 weeks. Motion should be started then to limit joint stiffness. Thereafter, flexion is limited to 90 degrees until radiographic evidence shows fracture healing. Nondisplaced fractures heal well in most circumstances; the most common complication is joint stiffness.
Most displaced fractures require surgical intervention. Tension band wiring or plating are the two most common techniques for fixation of an olecranon fracture.
Tension band wiring works well for transverse olecranon fractures that are not comminuted (Figure 3). Two parallel K wires are inserted through the tip of the olecranon and across the fracture site. A surgical wire is then placed in a figure eight pattern to apply tension. This tension band construct changes the deforming tension force of the triceps into a compressive force that favors healing.
Plate and screw fixation is used in more unstable fracture patterns (Figure 4). The plate is typically placed on the dorsal aspect of the ulna. Plate fixation is stable, has a high union rate and low rates of loss of motion or weakness.
In most instances, olecranon fractures heal well after surgery. The most frequent complication is annoying symptoms produced by the implanted hardware, which can be removed after the fracture has healed. Other possible complications include loss of reduction, infection, damage to the ulnar nerve, and elbow stiffness.
It is important to note that many low-demand older patients have poor skin and osteoporotic bone. They are at a very high risk of poor outcomes from surgery, including wound complications, infection, and fixation failure. In this cohort of patients, even displaced fractures should be considered for non-operative management with a supportive sling holding the elbow at 90 degrees. These patients should start gentle active range of motion exercises after the first week or two as the soft tissue swelling subsides and such motion will not be too painful. The fracture gap will heal with scar tissue. Thus, there will be some weakness in active extension. Nonetheless, the elbow can still extend, albeit weakly, and patients will have sufficient stability for acceptable function relative to limited demands.
Risk Factors and Prevention
Risk factors for olecranon fractures include any condition that increases the likelihood of falling. In addition, any disease that weakens the bone such as vitamin D deficiency, osteoporosis, or steroid use increases the risk.
Elbow pads may be useful when participating in high contact sports and activities such as bike riding, skateboarding and roller skating to protect against direct blows.
Trampolines are such a common cause of broken elbows and other bones in children that the American Board of Pediatrics issued a warning against their recreational use.
Although speakers of English in certain parts of the world, e.g. Boston, pronounce these words indistinguishably, the word “ulna” refers to the bone itself and the word “ulnar” is the adjectival form. “Ulnar” describes things related to or near the ulna bone (ulnar nerve, ulnar collateral ligament, etc.).
The word olecranon is of Greek origin whose first root “olene” means elbow and second root “kranion” means head.
Olecranon, ulna, radio-capitellar line, tension band wiring
Understand that olecranon fractures can be associated with other fractures and instability of the elbow. On exam, identify the swollen joint, and recognize open fractures, joint instability, fracture displacement, and neurovascular status. Understand that the failure of the extensor mechanism creates inability to extend the elbow against gravity but also that gravity can be used to allow passive extension – both a trap in examination for function and a blessing if normal fracture healing is prevented. Appreciate the effect of prolonged immobilization on elbow stiffness and associated functional impairment and disabilities. Interpret radiographs of the elbow and correctly identify fracture patterns and instability. Be able to immobilize the elbow until definitive treatment can be administered.