Lateral Humeral Condyle Fracture 

In 1883, Stimson first described the fracture patterns in lateral condyle fractures in his book Treatise on Fractures.^[1] He described the fracture as beginning in the lateral metaphysis proximal to the condyle, coursing distally, and exiting through the articular surface through the medial trochlear notch or through the capitellotrochlear groove. In 1955, Milch recognized the significance of these fracture patterns as they related to elbow stability.^[2] Thus, the fracture patterns of the lateral condyle bear his name and are classified as either Milch I or Milch II fractures.^{[3, 4, 5]}

The distal humerus is primarily cartilage at the age when these injuries typically occur, and knowledge of the secondary centers of ossification is necessary to understand the possible fracture patterns. Due to incomplete ossification, the fracture may appear subtle on radiographs as it courses through the cartilage anlage, as depicted in the images below.

The physis of the lateral condyle extends into the trochlear notch of the distal humerus (see image below). Therefore, in some fractures, the lateral crista of the trochlea may be part of the fracture fragment, leading to an unstable humeral ulnar articulation.

The difficulties related to treatment of this fracture are both biologic and technical. Biologic problems are a result of the healing process and may occur with appropriate treatment and anatomic reduction. These problems include lateral spur formation with pseudo cubitus varus and true cubitus varus. Technical difficulties are the result of errors in management and may result in nonunion, malunion, valgus angulation, avascular necrosis, or a combination of these conditions.

Frequency

Lateral condyle fractures, as depicted in the image below, account for 17% of all distal humerus fractures and 54% of distal humeral physeal fractures. The frequency of lateral condyle fractures peaks in children aged 6 years. Most fractures occur in children aged 5-10 years. Cases have been reported in patients as young as 2 years and as old as 14 years.

Two theories of the mechanism of injury for this fracture exist. The first is the pull-off theory, in which avulsion of the lateral condyle occurs at the origin of the extensor/supinator musculature. This may occur as a varus stress is applied to the extended elbow with the forearm supinated. This is thought to be the most common mechanism of injury. The second is the push-off theory, in which a fall onto the extended hand leads to impaction of the radial head into the lateral condyle, causing the fracture.^[6]

The lateral condyle fracture is a Salter-Harris IV fracture pattern and follows physeal injury principles. For more information about injuries of the growth plate, see Salter-Harris Fractures. The fracture fragments in these patients are primarily cartilaginous as a result of the young age of the patients. The radiographic interpretation may be misleading because the visible fragment appears smaller than the actual size and, in addition, the amount of displacement is not appreciated.

In lateral condyle fractures, the displacement is greater than appreciated, and incongruity of the articular surface is present. Fractures with minimal displacement must be carefully monitored, as they have a high tendency to displace. Once these displaced fractures consolidate in a malunited position, treatment is difficult, dangerous, and fraught with complications. For these reasons, surgical reduction should be performed and is recommended within the first 48 hours postfracture.^[7]

Children usually present with a history of a fall onto an extended arm. Patients present with pain and associated elbow swelling. Physical examination demonstrates a swollen elbow, pain greatest over the lateral condyle, and refusal of the patient to actively move the elbow. Occasionally, crepitus is present in an unstable fracture pattern. Significant deformity may indicate an elbow dislocation.

Operative management is essential for all displaced fractures and in those demonstrating joint instability or the potential for delayed joint instability.

Stage I, or type I, lateral condyle fractures with less than 2 mm of displacement may be treated with immobilization. If there is a question of stability or the possibility of delayed displacement in these type I fractures, percutaneous pinning is recommended. If the degree of fracture displacement is questioned, anatomic reduction and surgical stabilization is needed. Open reduction is indicated for all displaced type II and type III fractures.

Fractures that are not greatly displaced and are identified on a delayed basis greater than 3 weeks should not undergo surgical intervention. Healing has progressed to a point that extensive dissection would be required to achieve reduction leading to a high incidence of avascular necrosis of the lateral condyle.