Paediatric Monteggia Fracture-Dislocation
Monteggia fracture-dislocations are a less common injury compared to forearm fractures. However, it has been the subject of considerable investigation because of the frequency with which its diagnosis is missed and the serious sequelae that may develop without treatment.
The peak incidence is 4-10 years of age.
Monteggia fracture-dislocation classification is defined by the direction (i.e., anterior, posterior, or lateral) of the radial head dislocation.
Radial head displacement is always in the direction of the apex of the ulnar deformity.
In type I fracture (70%), which is common; the radial head is dislocated anteriorly.
Type I fractures are usually a result of a fall on an outstretched hand with hyperpronation or hyperextension of the forearm.
Type II fractures (5%) have posterior dislocation of the radial head.
Type II fractures occur when the flexed elbow is longitudinally loaded; the forearm may be in pronation, neutral position, or in supination.
Type III fractures (25%) are the second most common. The ulnar fracture is metaphyseal and often greenstick, and the radial head is dislocated laterally.
Type III injuries are most likely the result of a varus-extension force at the elbow.
Type IV fractures (rare) have a fracture of both the radius and ulna with anterior dislocation of the radial head.
The usual presenting complaint is pain and swelling over the elbow and proximal third of the forearm following a fall.
On examination, patients usually have an obvious deformity of the forearm and elbow.
Rotation of the forearm or flexion-extension of the elbow is painful and restricted.
The radial head may be palpable and displaced from its normal position in the direction of dislocation—anteriorly, posteriorly, or laterally.
Palpation of the ulnar diaphysis will reveal tenderness and deformity.
A careful examination of the skin and a careful neurovascular assessment should also be performed, with particular attention to the posterior interosseous nerve.
All fractures should be assessed using the Advanced Trauma Life Support (ATLS) principles to ensure associated and potentially significant injuries are identified.
Anteroposterior (AP) and lateral x-rays of the forearm that include the wrist and elbow should be ordered. There must also be a true AP and lateral view of the elbow (not just a forearm view) to assess the radiocapitellar joint.
Monteggia fracture-dislocations can be easily missed on x-ray.
If an ulna fracture is present, always look for a radial head dislocation. A line drawn down the shaft of the radius should point to the center of the capitellum (radiocapitellar line) in both AP and lateral x-ray views to exclude joint dislocation.
The posterior border of the ulna should also be assessed. It should be straight, not bowed. If it is not straight, it indicates a plastic deformation injury.
The reduction is always required and is urgent. This is usually performed in theatre under a general anesthetic.
Closed reduction and cast immobilization are indicated in all acute injuries.
The goal of treatment is to obtain and maintain an anatomically reduced radial head.
This can often be accomplished with a less than an anatomic reduction of the ulna.
Open treatment is indicated when anatomic reduction cannot be obtained or maintained by closed methods.
If the ulna cannot be maintained in a reduced position, the radial head will often re-dislocate when the ulnar fracture displaces.
In most cases, stabilizing the ulnar fracture will keep the radial head reduced. Ulnar fixation can be accomplished with pins, screws or plates.
Emphasis should be placed on the elevation of the limb (elbow above the heart) for the first 48 hours and active finger mobilization.
Back slab and sling should be worn under clothing and not through the sleeve.
If identified early, these injuries will do well. Approximately 90% of children with Monteggia fracture-dislocations have good to excellent results.
Physiotherapy is not recommended to regain range of motion (ROM).
Delayed diagnosis is the most frequent complication. Treatment after delayed diagnosis is much more complex and the outcomes are much less satisfactory.
Nerve injury – The radial nerve is the most commonly injured (10-20%). The posterior interosseous nerve can also be injured due to its proximity to the radial head. The injury is usually a neuropraxia. Peripheral nerve examination needs to be documented. The nerve injury is usually treated expectantly. The return of nerve function would be expected by approximately 9 weeks. Electromyography (EMG) assessment should be done at 12 weeks if nerve function is not returning.
Periarticular ossification – this can occur in 3-7% of Monteggia fracture-dislocations. This can be around the radial head or the annular ligament. It is associated with higher energy injuries, fractures of the radial head, and multiple attempts at manipulation. This can affect elbow ROM.
Stiffness after Monteggia fractures may be the result of simple immobilization, soft tissue ossification, myositis ossificans, or fibrous or bony synostosis between the proximal ulna and radius.