The surface of the radial head is covered with cartilage, and its central part is concave and cup-shaped, opposing the articular surface of the humeral capitulum. When the elbow joint is extended, only the anterior half of the radial head contacts it. During elbow flexion, the two surfaces fully align. The ulnar side of the cup-shaped surface features a crescent-shaped inclined plane that contacts the radial edge of the trochlea during pronation. The periphery of the radial head is also covered with cartilage, known as the cylindrical rim, which forms the superior radioulnar joint with the radial notch of the ulna. The radial head is not perfectly circular but elliptical. Measurements on fresh specimens at Beijing Jishuitan Hospital showed a long axis of 24 mm and a short axis of 21 mm, with a ratio of long to short axis of 8:7. The incidence is lower in children and more common in adults.

bubble_chart Etiology

Fractures caused by direct external force are rare. The common scenario is falling with the elbow in an extended position and the palm hitting the ground, where the external force causes the radial head to collide with the capitulum of the humerus in a valgus position, resulting in a fracture. It is often accompanied by injury to the capitulum of the humerus and the medial collateral ligament. This condition is more common in adults and is prone to misdiagnosis. If not treated early, some patients may experience restricted forearm rotation function, necessitating the removal of the radial head. Based on the fracture morphology, it can be classified into the following types.

(1) Crack type: This is a linear fracture without displacement. The fracture line typically runs from the lower lateral to the upper posterior, reaching the articular surface. The annular ligament is uninjured, providing stability to the fracture and preventing further displacement.

(2) Depressed fracture: The articular surface of the radial head is compressed and collapses.

(3) Comminuted fracture: In cases without displacement, the shape of the radial head is preserved, and the articular surface remains intact. The annular ligament is also intact. In cases with displacement, the annular ligament is often injured.

Local pain, grade I swelling on the lateral side of the elbow, with obvious tenderness around the radial head. Limited forearm rotation, pain during passive movement, especially noticeable during supination. Elbow flexion and extension are not restricted, but painful during movement.

X-ray imaging can confirm the diagnosis and type.

bubble_chart Treatment Measures

Fracture, after short-term internal fixation, can begin movement. Generally, if there is little displacement, traction is applied in the extended position, and the forearm is rotated in the adducted position to restore the radial head fracture to its round or near-round shape to avoid hindering forearm rotation. After reduction, a gypsum splint is used for fixation. The gypsum splint is removed after 2-3 weeks to practice elbow joint movement. For comminuted fractures with displacement or unsatisfactory reduction, early radial head resection should be considered, but the surgery is limited to adult patients. The resection should not go below the articular surface of the radial tuberosity. After smoothing the fractured end and removing surrounding bone fragments, the surrounding soft tissue is sutured over the rough surface of the radial fracture. Postoperatively, the elbow joint is suspended in the functional position with a triangular bandage, and movement can begin after 2 weeks.