Monteggia Fractures
A Monteggia fracture is not a simple fracture. It is a fracture of the proximal ulna along with a dislocation of the radial head. It can happen in both children and adults. However, it is one of the most common missed injuries in children seen in the emergency room. Along with the ulna fracture, the radial head may be dislocated or subluxed, and this problem may not be clear on x-rays. If this injury is missed, the child will probably need a large surgery later on to deal with is big problem. To check, a line drawn from the proximal radius should bisect the capitellum in all x-ray views. If there is ever any doubt, get x-rays of the other side to compare. It should be made a practice to look at the radius and the radial head when there is a fracture of the proximal ulna, so as to not miss the diagnosis of Monteggia fracture. The position of the radial head in relation to the capitellum should be examined
The treatment of a Monteggia fracture depends on the age of the patient. In general, pediatric patients will have a closed reduction of the ulna and closed reduction of the radial head performed. In adult patients, open reduction and internal fixation of the ulna with a dorsal plate, and closed reduction of the radial head will be performed.
The most common type of Monteggia fracture is an anterior Monteggia fracture. That means that the apex of the fracture is anterior, and the radial head goes anteriorly. The anterior Monteggia fracture is more common in children. Posterior Monteggia fractures constitute 70–80% of Monteggia fractures in adults.
There are four types of Monteggia fractures. These fractures are classified according to the direction of displacement of the radial head. The radial head has two relations. One is the relation with the capitellum, and the other is the relation with the proximal radioulnar joint. When the radial head subluxes or dislocates, it does so from these two joints. When this happens, the radial head becomes free. This means that the radius is not connected to the capitellum or the superior radioulnar joint.
Type I is a fracture of the middle or proximal third of the ulna with anterior dislocation of the radial head. It has the identifying characteristic that the apex of the ulna fracture is anterior. This is the most common of all types, especially in children (about 60%). For children, the fractured ulna and the dislocation of the radial head should be reduced, and the elbow should be immobilized in flexion and supination. When the elbow is flexed, especially more than 90 degrees, the biceps will relax. However, the circulation then needs to be watched.
Type II is the posterior type of Monteggia fracture. This is the most common type of Monteggia fracture seen in adults. About 15% all Monteggia fractures are type II posterior. It is also associated with higher complication rate and carries the worst prognosis. The fracture pattern is a fracture of the middle or proximal third of the ulna with posterior dislocation of the radial head. A defining characteristic is that the apex of the fracture is posterior. To treat, the elbow should be immobilized in extension.
Type III is the lateral Monteggia fracture. These account for about 20% of all Monteggia fractures. The fracture pattern is a proximal ulna fracture with lateral dislocation of the radial head.
Type IV is a rare type of Monteggia fracture, and only accounts for about 5% of all Monteggia fractures. The fracture pattern is a fracture of the proximal ulna with anterior dislocation of the radial head, and also a fracture of the proximal third of the radius below the bicipital tuberosity. In this case, there is an extra fracture of the radius that needs to be attended to. Every patient will need surgery for a type IV Monteggia fracture, even children.
The posterior interosseous nerve is adjacent to the radial neck, placing it as risk for a traction injury with dislocation of the proximal radius. Nerve injury that involves the posterior interosseous nerve is not uncommon with Monteggia fractures. Because of this, patients with Monteggia fractures should have a neurovascular examination done. The patient should be asked to “hitchhike” and extend the fingers. The wrist should be in dorsiflexion when the patient extends their fingers. In the case of an interosseous nerve injury, the finger extensors will not be working, and the patient will not be able to perform the tasks asked above.
If the posterior interosseous nerve is injured, the patient should simply be observed. If there is a posterior interosseous nerve injury with a Monteggia fracture, the fracture needs to be reduced and stabilized, as does the radial head dislocation. However, the nerve should not be explored, rather just observed. Typically with Monteggia fractures, the nerve injury is a neuropraxia. This can be expected to resolve itself in 6–12 weeks, and should simply be observed during this time. If the nerve injury does not resolve, EMG and nerve studies should be done after the period of observation.
For Monteggia fractures in children, the ulnar shaft fracture should be checked carefully. Any time that there is an ulnar shaft fracture or any fracture of the proximal ulna, the radial head position should be looked at. It should be observed that the radial head is reduced to the capitellum, and it should be noted that the subluxation may be subtle. Recognition of a Monteggia fracture in children is important. Early appropriate treatment is much easier than treating a missed radial head dislocation.
The treatment for adult patients with Monteggia fractures is to perform an open reduction internal fixation of the ulna. Then, when the ulna is properly aligned and fixed, the radial head will reduce by itself. After fixation of the ulnar fracture, if the radial head is still not reduced, then assess the ulnar reduction. Check for malalignment or malreduction of the ulna. It is imperative to restore the length and the proper alignment of the ulna, so that the radial head can be reduced. If the ulna is malaligned, then the radial head will remain subluxed. In these cases, radial head instability may be caused by non-anatomic reduction of the ulna or by interposition of the annular ligament. However, the fracture of the ulna may be too comminuted and it may not be reduced properly, and may then need bone grafting later on for healing.
A Monteggia variant associated with radial head fracture, in addition to dislocation of the radial head and fracture of the ulna, can be a problem. If this is the scenario, the radial head fracture is usually fixed or replaced, and a prosthesis is used to replace the radial head in the elderly, especially if the fracture is comminuted. Then, the subluxation of the radial head is reduced and the fractured ulna is fixed as usual.
For children, the radial head ossifies around the age of 4. The treatment for children with types I, II, and III Monteggia fractures is to perform a closed reduction of the ulna, in order to restore the length of the ulna, and a closed reduction of the radial head. Closed reduction is much more successful in children compared to adults. For anterior Monteggia fractures, the elbow is immobilized in flexion and supination. For posterior Monteggia fractures, the elbow is immobilized in extension. Ulnar fixation with a rod or plate is only needed in older patient with unstable fractures.
To treat a missed or neglected Monteggia fracture in children, an osteotomy of the ulna should be performed, and also a lengthening with correction of the angulation. Then, reduction of the radial head in addition to plating of the ulna should be performed. The patient may need an open reduction of the radial head.
All type IV Monteggia fractures, both in children and adults, will require surgery to treat. For children with type IV fractures, closed reduction of the radial head with intramedullary pin fixation of the radius and ulnar shaft should be performed. The radius and ulnar shaft fractures are stabilized surgically in order to give a lever arm for reduction of the radial head. In this type of fracture, the radial head subluxation may be missed or unappreciated because the focus is usually on the multiple forearm fractures.
Surgery is also done in cases where proper ulna length is not achievable, the ulna is not able to be reduced, or the radial head is not able to be reduced. In these situations, and IM rod or a plate is used.
