Elbow Fractures Overview

Excerpt

Anatomy

The elbow is a complex hinge-and-pivot joint formed by 3 articulations: the humeroulnar joint between the trochlea of the humerus and the ulnar notch, permitting flexion and extension; the humeroradial (radiocapitellar) joint between the capitellum of the humerus and the radial head, which allows both rotation and flexion-extension movements; and the proximal radioulnar joint between the proximal ulna and radius, enabling forearm pronation and supination. These 3 articulations are enclosed within a single synovial sheath (see Image. Medial and Volar Views of the Right Elbow).

Stability of the elbow is maintained despite its broad range of motion (ROM), which spans from 0° in full extension to 150° in full flexion, and approximately 80° in both supination and pronation. The radial head and the annular ligament contribute significantly to proximal forearm stability (see Image. Ligamentous Anatomy of the Right Elbow).

The coronoid process plays a critical role in elbow joint stability by preventing posterior translation of the ulna relative to the humerus. As an attachment site for the lateral ulnar collateral ligament and the anterior band of the medial collateral ligament, the coronoid contributes to resistance against varus and valgus stress. Axial load is primarily transmitted through the radiocapitellar joint, particularly in extension. The olecranon limits anterior translation of the humerus.

The medial epicondyle serves as the common origin for the superficial forearm flexor-pronator group, including the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, pronator teres, and flexor digitorum superficialis. The lateral epicondyle provides attachment for several extensor muscles and the supinator, including extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris.

The elbow consists of 3 bones: the distal humerus, which includes the condyles and the articular surfaces (trochlea and capitellum); the proximal ulna, composed of the olecranon and coronoid process; and the proximal radius, defined primarily by the radial head. Several common elbow fracture types involve these anatomic components, discussed below.

Supracondylar Fracture

Fractures of the distal humerus just above the elbow, known as supracondylar fractures, account for approximately 60% of all elbow fractures in children. These injuries primarily affect the immature skeleton and occur most commonly in younger age groups. Based on the mechanism and direction of distal fragment displacement, supracondylar fractures are classified as either extension- or flexion-type.

Extension-type fractures account for more than 95% of cases and result from a fall onto an outstretched hand (FOOSH) with the elbow in full extension. The transmitted force is directed toward the olecranon fossa, a structurally vulnerable site. Posterior displacement of the distal fragment is typical. Nondisplaced fractures may be radiographically subtle, with indirect signs such as a posterior fat pad, anterior sail sign, or disruption of the anterior humeral line.

The radiographic classification of extension-type fractures is as follows:

1. Type I: Nondisplaced or minimally displaced

2. Type II: Displaced, with intact posterior cortex

3. Type III: Completely displaced, with disruption of both cortices

Flexion-type fractures occur in less than 5% of cases and result from direct anterior trauma to a flexed elbow, leading to anterior displacement of the distal fragment. These injuries frequently involve posterior periosteal disruption and are often open due to the direct force.

Flexion-type fractures are classified as follows:

1. Type I: Nondisplaced or minimally displaced

2. Type II: Incomplete fracture with intact anterior cortex

3. Type III: Completely displaced with proximal and anterior migration of the distal fragment

Neurovascular injury is a major complication, particularly involving the brachial artery and median nerve due to their proximity to the fracture site (see Image. Course of the Median Nerve in the Forearm). Prompt recognition and management are essential to prevent long-term morbidity.

Gartland classification

Supracondylar fractures are classified according to the degree of displacement, with extension-type fractures comprising the vast majority of cases. The Gartland classification categorizes extension-type fractures as follows:

1. Type I: Nondisplaced or minimally displaced fracture. Radiographic visualization may be difficult, as the fracture is often occult. The anterior humeral line continues to intersect the anterior half of the capitellum. A positive fat pad sign may be the only radiologic clue (see Image. Posterior Fat Pad Sign in Supracondylar Fracture).

2. Type II: Posteriorly displaced fracture with an intact posterior cortex.

3. Type III: Completely displaced fracture with disruption of both cortices. Posteromedial displacement occurs in approximately 75% of cases, while posterolateral displacement is seen in 25%.

4. Type IV: Involves complete circumferential periosteal disruption and results in multidirectional instability, with loss of stability in both flexion and extension. Although not part of the original Gartland classification, this type has important management implications, as closed reduction may be challenging and often requires surgical fixation with careful intraoperative assessment of stability.

In flexion-type supracondylar fractures, the distal fragment is displaced anteriorly due to direct trauma to a flexed elbow. These fractures are less common than extension-type injuries and are often associated with high-energy trauma.

Lateral Condyle Fracture

Lateral condyle fractures are the 2nd most common type of elbow fracture in children, accounting for 15% to 20% of all cases. These injuries involve the lateral condyle of the distal humerus, the outer bony prominence of the elbow. The peak incidence occurs between the ages of 4 and 10 years. Most lateral condyle fractures are classified as Salter-Harris type IV, involving the metaphysis, physis, and epiphysis.

Two classification systems are commonly used to describe these fractures. The Milch classification describes lateral condyle fractures based on the location of the fracture line relative to the trochlear groove. In Milch type I, the fracture line lies lateral to the trochlear groove. In Milch type II, the fracture extends through the groove. Although Milch type II is more commonly observed, this classification alone does not reliably predict elbow instability. Current management decisions are based more on the degree of displacement and the extent of articular and soft tissue involvement rather than the fracture line’s position within the trochlea.

The displacement classification categorizes fractures based on the degree of displacement. Type 1 fractures exhibit less than 2 mm of displacement. Type 2 fractures show displacement between 2 mm and 4 mm, with the fragment remaining near the humerus. Type 3 fractures are widely displaced with disruption of the articular surface.

Medial Epicondyle Fracture

Medial epicondyle fractures are the 3rd most common type of elbow fracture in children. These extra-articular injuries involve the apophysis of the medial epicondyle, located on the posteromedial aspect of the elbow. The typical age of occurrence is between 9 and 14 years, with a higher incidence in boys. These fractures frequently result from athletic activities such as football, baseball, or gymnastics. Common mechanisms include posterior elbow dislocation or repetitive valgus stress, as seen in repeated overhead throwing. This overuse mechanism is often referred to as "Little League elbow." Clinical presentation includes medial elbow pain, tenderness over the medial epicondyle, and valgus instability.

Radial Head and Neck Fracture

Radial head fractures are more common in adults and account for approximately 1/3 of all elbow fractures. In children, these fractures most often follow a Salter-Harris type II pattern, with the fracture line traversing the physis and extending into the metaphysis. Hemarthrosis is a frequent finding following this kind of injury due to the radial head’s rich vascular supply.

The Mason classification system describes radial head fractures based on displacement and associated injuries. Type I fractures are nondisplaced and involve less than or equal to 2 mm of displacement. Type II fractures are displaced by more than 2 mm. Type III fractures are comminuted. Type IV fractures are associated with elbow dislocation.

Olecranon Fracture

Olecranon fractures account for approximately 10% of elbow fractures (see Image. Occult Olecranon Fracture on Lateral Elbow Radiograph). The olecranon is the most proximal portion of the ulna, extending from its tip to the coronoid process. The olecranon curves around the distal humerus and articulates with the trochlea to form the posterior aspect of the elbow joint. All olecranon fractures are intra-articular and involve the point of insertion of the triceps tendon. These fractures are relatively uncommon in children and are frequently associated with concomitant injuries, particularly radial head or neck fractures. A transolecranon fracture-dislocation represents a complex injury involving both fracture and elbow joint dislocation.

The fracture pattern depends on the mechanism of injury. Comminuted fractures typically result from a direct fall onto the elbow, whereas noncomminuted fractures often occur following a FOOSH. The degree of elbow flexion at the time of trauma influences both the location and morphology of the fracture.

Coronoid Fracture

The coronoid process, the anterior-most bony prominence of the proximal ulna, serves a critical stabilizing function by resisting posterior translation of the ulna. Fractures of the coronoid process occur in approximately 10% to 15% of elbow dislocations.

The Regan and Morrey classification describes coronoid fractures according to the extent of involvement. Type I fractures involve only the tip of the coronoid. These injuries often appear stable, but instability may occur in the setting of ligamentous disruption or terrible triad injuries. Type II fractures involve up to half of the coronoid process and may compromise ulnohumeral stability. Type III fractures affect more than half of the coronoid and are frequently associated with posterior elbow instability.

Monteggia Fracture

A Monteggia fracture involves a fracture of the proximal ulna with dislocation of the radial head at the elbow. Although the radius appears intact on initial imaging, this injury demands a high index of suspicion for radial head dislocation in any patient with a proximal ulnar fracture. The most common mechanism is a FOOSH, resulting in hyperpronation. Alternative mechanisms include a direct posterior blow to the ulna or a fall on a flexed elbow.

Monteggia fractures are frequently missed, making them one of the most commonly overlooked serious elbow injuries. Delayed or missed diagnosis is not uncommon, often leading to poor functional outcomes. Careful assessment of the radiocapitellar alignment is essential in any case of ulnar fracture to avoid overlooking a radial head dislocation.

Capitellum Fracture

Capitellum fractures are uncommon, accounting for fewer than 1% of adult elbow fractures. These injuries usually result from high-energy trauma, such as a direct blow or fall. Capitellar fractures are often difficult to detect on plain radiographs and may require advanced imaging, such as computed tomography (CT), for definitive diagnosis.

Terrible Triad Injury

The terrible triad injury consists of a posterolateral elbow dislocation combined with fractures of the radial head and the anterolateral facet of the coronoid process (see Image. Terrible Triad Injury on Lateral Elbow Radiography). This injury complex also includes disruption of the lateral ulnar collateral ligament and is associated with significant instability and an unpredictable clinical outcome.

Fracture Classification by Joint Involvement

Elbow fractures may be classified based on joint involvement. Extra-articular fractures include supracondylar, epicondylar, condyle, and intercondylar fractures that do not involve the articular surface. Intra-articular fractures involve components of the joint surface, such as the trochlea, capitellum, radial head, and proximal ulna.