Presentation

The patient normally presents with pain and a history of either a fall onto the arm or a direct blow to the forearm. In type I or IV injuries the forearm is usually held in pronation. Elbow movements are limited by pain and swelling. Usually the ulna fracture can be palpated and the direction of angulation identified. Assessment of the neurovascular state of the hand and forearm is of paramount importance, particularly with type II injuries, as these are quite commonly associated with a posterior interosseous nerve neuropraxia.

Investigations

Anteroposterior and lateral radiographs of the elbow, forearm and wrist are essential in order to avoid missing a Monteggia fracture–dislocation. Inadequate radiographs may fail to show the radial head dislocation, resulting in the patient being inappropriately treated for an isolated ulna fracture. The reported incidence of misdiagnosis varies from 16%⁸ to 52%.⁹

If doubt exists as to the extent of the patient’s injury, it is appropriate to obtain a CT scan of the elbow with three-dimensional reconstruction views in order to clearly define the anatomy of the radiocapitellar joint (Fig. 23.2).

Figure 23.2 Bado type II Monteggia fracture dislocation. (A, B) The radiographs do not show the exact anatomy of the proximal ulna fracture. (C, D) CT 3-D reconstruction of the same patient clearly identifies the fracture morphology.

In the case of a highly comminuted type IV injury, plain radiographs of the contralateral forearm may be helpful in order to allow the true length of the radius and ulna to be measured.

Treatment options

Anecdotal reports of adult Monteggia fracture dislocations show a poor outcome with conservative management – specifically a painful stiff elbow with limited forearm rotation, particularly supination.

In 1940 Speed and Boyd⁹ published their results of treating 30 acute and 32 chronic Monteggia type I fracture dislocations. They advocated open reduction and internal fixation of the ulna fracture and if needed reconstruction of the annular ligament with a ‘fascial loop’. In 1969 a further report from the same unit with 159 cases re-emphasized the importance of surgical management.¹⁰ This has also been recommended in other studies.^11,12

Currently the accepted treatment option for adult Monteggia fracture dislocations is open reduction and rigid anatomical fixation of the ulnar fracture. Once this has been performed the radial head will either spontaneously reduce or will be reducible by closed manipulation.¹² If, however, in addition to the radial head dislocation, there has been a radial head fracture then consideration must be given to reconstruction, excision or replacement of the radial head.

The treatment of paediatric Monteggia fracture dislocations is discussed in Chapter 12.

Surgical technique

Preoperative planning is of paramount importance. The radiographs/CT scans must be carefully inspected for evidence of a radial head or coronoid fracture. If present, the surgical approach must enable access to these important structures since a failure to address these fractures can result in instability and poor outcome (Fig. 23.3).

Figure 23.3 (A) This patient’s complex Monteggia fracture–dislocation included a radial head and coronoid fracture. (B) Initial fixation failed to address these injuries and as a result the elbow dislocated posteriorly due to the lack of an anterior buttress. Note that the elbow dislocated in a plaster backslab, indicating that instability cannot be controlled by external plaster cast immobilization. (C, D) Acute revision surgery addressed the coronoid fracture (note the long screw in the middle of the plate capturing the coronoid fragment). The radial head was not salvageable due to comminution and replacement was undertaken. The elbow then became stable throughout the range of movement.

The patient is placed supine on the operating table with the injured arm across the chest. A small sandbag is placed under the ipsilateral shoulder and a high tourniquet applied to the arm in order to provide a bloodless field.

A dorsal skin incision is utilized and centred over the ulna fracture. The length of the incision is determined by the comminution and complexity of the fracture. Skin flaps are then raised and should be as thick as possible to avoid devascularization and the risk of postoperative skin edge necrosis.

The ulnar fracture is identified. A two-part fracture can normally be reduced without great difficulty. Comminuted fractures, however, are more demanding, particularly if they involve the coronoid. In our experience the coronoid fragment is often displaced anteriorly and proximally. In this situation we have found it helpful to reflect the proximal ulnar fragment away from the surgical field as per an olecranon osteotomy. This facilitates identification of the coronoid fragment and allows reduction and temporary K-wire fixation of the fracture fragments from distal to proximal. The size of the coronoid fracture dictates the fixation method. If the fragment is large enough to accept one or two cortical screws, then these are inserted from the larger to the smaller fragments (Fig. 23.4). If the coronoid fragment is small, a fibre-wire suture is inserted in the anterior capsule and later tied around the ulna after the reconstruction has been completed. Once the coronoid fracture has been controlled the proximal ulnar fragment is anatomically repositioned and reduced to the reconstructed ulnar shaft.

Figure 23.4 (A, B) A type 2 Monteggia fracture dislocation with a fracture of the dislocated radial head. (C, D) The coronoid fragment was captured with screws inserted using the large to small fragment fixation principle. This reconstructs the anterior buttress of the elbow joint, preventing redislocation.

Definitive fixation is then undertaken using a plate applied to the dorsal ridge of the ulna.¹³ This plate acts as a tension band device, neutralizing flexion moments at the fracture site during normal postoperative movement. Plates applied to the flatter medial or lateral surfaces of the ulna may result in failure of the metalwork and posterior angulation at the fracture site.⁵ The fixation should be robust enough to resist postoperative displacement forces until union has occurred. This can be achieved by contouring a low-profile compression plate¹⁴ or by using a pre-contoured anatomical proximal ulnar plate. The latter has the advantage that if the plate does not fit the ulna it is most likely that the bone is in the wrong position. Once the ulna has been anatomically reconstructed the radial head will spontaneously reduce in approximately 87% of cases¹⁵ or can be reduced by closed manipulation. This must be confirmed intraoperatively with a true lateral radiograph.

Occasionally the radial head becomes trapped and does not reduce. Structures that have been identified as preventing reduction include a tear of the capsule, the radial nerve¹⁶ and the biceps tendon wrapping around the radial neck.¹⁵ If closed reduction of the radial head cannot be achieved, open reduction must be undertaken, usually via a separate Kocher incision.

Radial head fractures occur commonly with Monteggia fracture dislocations and have a reported incidence in type II injuries of 70%.¹⁴ Provided they are recognized preoperatively the dorsal skin incision can be placed slightly more radially and extended more proximally. This will enable the radial skin flap to be elevated sufficiently such that a Kocher approach can be made to the radial head without the need for a separate skin incision.

We often perform osteosynthesis of the fractured radial head prior to fixation of the ulnar fracture as we have found this provides greater stability to the elbow and facilitates fixation of the ulna.

If the fractured radial fragment is very small and unfixable, it is our practice to excise the fragment. However, excision of fragments involving more than 20% of the head can render the joint unstable.¹⁷ In this situation we excise the radial head and perform a radial head arthroplasty (Fig. 23.5).

Figure 23.5 (A, B) Preoperative radiographs show a comminuted proximal ulna fracture with a radial neck fracture. The radial head is completely separate and displaced posterior to the distal humerus. Radial head replacement was performed and the proximal ulna plated. (C, D) Postoperative images confirm an anatomical reduction and a stable joint.

Rehabilitation

Postoperatively a backslab is applied with the elbow in approximately 90° of flexion and with the forearm in moderate supination. This is maintained for between 2 and 3 weeks, with weekly radiographs to confirm that the radial head remains reduced. After removal of the backslab the patient begins progressive range-of-movement exercises. Strengthening exercises start at approximately 3 months, depending on the clinical and radiological progress. Heavy manual activity should be deferred for a period of at least 6 months from the time of reconstruction.

Radial nerve/posterior interosseous nerve palsy

The incidence of radial nerve palsy has been reported at between 3% and 30%.^10,18 Expectant management is recommended, as the majority (94%) are neuropraxias and will normally show signs of recovery within 9 weeks of the fracture–dislocation. The most likely mechanism of injury is stretching of the nerve at the time of the radial head dislocation. The nerve is especially at risk in type II lesions. Stein et al, however, in a series of seven radial nerve palsies explored six which failed to recover.²¹ They noted a tight arcade of Frohse that they felt was responsible for compression of the nerve. When this was released, improvement in nerve function was noted. They argued that if the radial nerve is non-functioning then an expectant approach is acceptable. However, if only the posterior interosseous nerve is affected, the probability of a tight arcade of Frohse is high and warrants a more aggressive approach with surgical decompression if nerve recovery has not occurred by 3 months.

Non-union

If a stable construct is used and good fracture compression achieved at the time of primary surgery, the rate of non-union is low. However, in more comminuted fractures (IID and IV) with a greater severity of initial injury the chance of non-union increases. If this occurs, revision fixation with bone grafting is appropriate and will usually lead to fracture union. It is important, however, with non-unions to exclude an underlying infection since if present an aggressive debridement is required and the application of an external fixator may also be necessary.²²

Stiffness

Contracture of the soft tissues around the elbow after trauma is well recognized. Anteriorly this involves the anterior capsule and brachialis, reducing elbow extension, while posteriorly the posterior capsule becomes thickened, reducing elbow flexion. In addition, failure to anatomically reduce the bony fragments at the time of reconstruction will result in bony impingement and a reduced range of elbow flexion and extension. The average flexion extension arc as reported in the literature is approximately 100° with supination of 55°. If the final range of movement achieved presents a functional problem for the patient an arthrolysis can be considered (Ch. 29).

Proximal radio-ulnar synostosis following a Monteggia fracture–dislocation occurs in less than 5% of cases.¹⁸ If encountered, surgical removal of bony bars may be appropriate. In our experience, however, there is often a soft tissue element to the restricted rotation such that even after removal of the heterotopic bone rotation remains limited. To reduce the risk of recurrence a prophylactic dose of radiotherapy immediately prior to surgery or the use of indomethacin postoperatively has been recommended,²³ although more recent literature has questioned the safety of radiation as it could potentially increase the risk of non-union.²⁴

Instability

Immediate postoperative recurrent radial head dislocation is unusual provided that the ulna has been anatomically reduced. The congruency of the radial head reduction should, however, be ensured intraoperatively both clinically and radiographically and this information should be clearly documented.

If the radial head does redislocate, revision of the ulnar fixation and/or an open approach to the radial head to remove interposed soft tissues will be required.

Missed Monteggia fracture–dislocation

This results from a failure to accurately identify the injury at the time of initial presentation. Most often the ulnar fracture is appreciated but the radial head dislocation remains unrecognized. In addition, if the reconstruction of the ulna is not anatomical the radial head will remain subluxed or dislocated. In this situation, if there is significant compromise of the patient’s function it is necessary to osteotomize, replate and bone graft the ulna and excise the radial head if it does not accurately reduce.