Fractures of distal humerus

Anatomical prerequisites and biomechanics

Structurally, the distal humerus consists of two columns. Their distal parts form the condyles with articular surfaces:

• The medial condyle forms the trochlea (trochlea).
• The lateral condyle forms the capitulum (capitulum).

Extra-articular elements—the epicondyles (epicondyli)—are located above the articular surfaces. The forearm flexors attach to the medial epicondyle, and the extensors to the lateral one. The bone is critically thinned between the condyles, where the coronoid fossa (fossa coronoidea) anteriorly and the olecranon fossa (fossa olecrani) posteriorly converge. This anatomical "weak link" determines the typical fracture lines.

Major nerves and the brachial artery run directly along the bone in this zone, rendering any displacement of bone fragments potentially catastrophic for the blood supply and innervation of the limb.

Classification (AO/ASIF) and mechanism of injury

Injuries to the 13th segment are divided into three principal types depending on joint involvement:

1. Type A (Extra-articular): Metaphyseal fractures. They predominantly occur via an indirect mechanism. The most common variant is the extension type (falling on a hyperextended arm), while the flexion type (falling on a flexed elbow) is less frequent.
2. Type B (Partial intra-articular): Part of the articular surface maintains continuity with the bone diaphysis. Fracture of the lateral condyle occurs upon falling on an abducted hand, whereas medial condyle fracture occurs upon falling on an adducted hand.
3. Type C (Complete intra-articular): The articular surface is completely detached from the diaphysis and disrupted. This is typical for high-energy motor vehicle accidents or direct falls onto the elbow, where the olecranon acts as a wedge, splitting the condyles and driving between them.

Clinical presentation and diagnostics

Rapidly increasing edema and extensive hematoma often mask the true bone deformation. The gold standard for diagnostics is radiography in two projections. If the patient cannot straighten the arm for the anteroposterior view due to pain, a CT scan or a comparative radiograph of the healthy joint is prescribed.

• In Type A fractures: Tenderness is noted above the joint. In extension injuries, the forearm appears shortened, and the olecranon is sharply outlined posteriorly. In flexion injuries, the forearm appears lengthened.
• In Type B fractures: Anatomical landmarks are altered. Marx's sign is disrupted (the axis of the humerus ceases to be perpendicular to the line of the epicondyles), and asymmetry of Hueter's triangle occurs. An attempt to rotate the forearm causes sharp pain.
• In Type C fractures: The elbow is catastrophically enlarged in width. Active movements are impossible, and passive movements reveal pathological lateral mobility.

Differential diagnosis must be performed to rule out forearm dislocations. Unlike a fracture, a dislocation presents with the springy resistance sign and lacks bone crepitus.

Complications: neurovascular bundle

In any distal humerus trauma, the physician is obligated to immediately check the pulse at the wrist and finger sensitivity. The types of displacement dictate the risks:

• The sharp edge of the proximal fragment in an extension fracture frequently contuses or lacerates the brachial artery (risk of acute thrombosis) and the median nerve.
• If the distal fragment is displaced posteriorly, the radial nerve is put at risk.
• Deviation of the lower fragment toward flexion or its rotation entails the risk of ulnar nerve injury.

Important: If a humeral fracture is accompanied by radial nerve palsy, emergency surgical treatment alone with nerve exploration and osteosynthesis is indicated.

Principles of treatment

At the prehospital stage, attempts at reduction (repositioning) without an X-ray are strictly prohibited. The limb is immobilized with a ladder splint or a Desault bandage, and analgesics are administered.

Conservative treatment Is used for fractures without displacement (girdle immobilization from the fingers to the shoulder joint for 3–4 weeks in a flexion position of 90–100°). In Type A displacements, a one-stage manual reduction under anesthesia is possible. The vector of traction and manipulation (pronation/flexion or extension) depends on the fracture type. If the fragments are unstable, the Judet method (percutaneous Kirschner wire fixation) or skeletal traction via the olecranon is used. After 3 weeks, a thoracobrachial cast is applied.

Surgical treatment (Osteosynthesis) Is the method of choice for intra-articular injuries (Type B and especially Type C), as closed reduction cannot perfectly restore joint congruence. Contoured locking compression plates, cancellous screws, and wires are used. For open fractures, external fixation devices (KFA) are employed. Stable internal osteosynthesis is the primary condition for early rehabilitation and mobilization of movements in the elbow joint.

Class and exam questions

What else to study on this topic

• Technique of skeletal traction via the olecranon
• Biomechanics of reduction in flexion and extension fractures
• Types and selection of bone plates for distal humerus osteosynthesis
• Early and late complications of diaphyseal and metaphyseal fractures
• Algorithm for neurological examination in elbow joint injuries

Other topics in the "Specialized Adult Traumatology" section

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