An Undescribed Monteggia Type 3 Equivalent Lesion: Lateral Dislocation of Radial Head with Both-Bone Forearm Fracture

Monteggia fractures are accepted as hard-to-recognize and easy-to-handle fractures. Adequate radiographic investigations and clinical examinations are necessities. This case holds unique features involving diagnosis and treatment. In this case, the radial head was dislocated laterally while both bones were fractured in the proximal diaphysis, being the first to be mentioned in the literature. Closed reduction of the ulna is the preferred method of handling and almost always results in reduction of the radial head. Literature obligates ulnar reduction as a preliminary to reduce and stabilize the radial head. Closed reduction reduced the ulna but the radial head was not reduced. Hence an intramedullary K-wire was used to reduce the radial head and a long arm cast was used to stabilize the reduction. The operation was successful and follow-up showed no complications.


Introduction
A Monteggia fracture is by definition a radial head dislocation with a concomitant ulnar fracture.
Obtaining as well as interpreting adequate and goodquality radiographs properly is the most important step in successful recognition and treatment of Monteggia fractures. Preventing delayed diagnosis is a major concern.
Bado classified four subtypes while adding another subtype group as Monteggia equivalent injuries. There are many types mentioned in the literature. However, there was no case reporting any lateral dislocation of the radial head with concomitant fracture of both bones.
Treatment with a radial implantation only, although literature suggests preliminary ulnar fixation, was also successful in our case without any complication.

Case Presentation
A 5-year-old patient was sent to our orthopaedic outpatient clinic from another emergency clinic with a diagnosis of a both-bone forearm fracture. It was reported that he fell on his hand. His arm was stabilized with a long arm aircast when he came, but no intervention of any kind was performed. Existing forearm biplanar radiographs obtained in the outside clinic confirmed the diagnosis (Figure 1).
There were no true elbow radiographs. Closed reduction and cast application were performed. Control radiographs revealed a lateral radial head dislocation. Operative intervention was planned and performed.

Investigations.
Existing radiographs showed no true elbow views and forearm radiographs were taken under suboptimal conditions (Figure 1). After our closed reduction, biplanar forearm and elbow radiographies were taken of both arms ( Figure 2). drawn along the long axis of the radial neck, which should bisect the capitellum on all projections [1]. Therefore an anterior radial head dislocation was excluded.

Differential
In case of a Monteggia fracture-dislocation, both bone forearm fractures exist with anterior displacement of radial head according to the Bado classification [2]. Radiographs taken after closed reduction and cast application, however, revealed a lateral dislocation of the radial head ( Figure 2). The ulna was reduced ( Figure 3). Operative intervention was planned.
Case Reports in Orthopedics

Treatment
The ulna was anatomically reduced after closed reduction ( Figure 3). An intramedullary Kirschner wire was implanted into the radius. Intraoperative fluoroscopy images revealed the successful reduction of the radial head and proved the already reduced ulna to be stable. No surgical intervention for stabilization of ulna was planned and a long arm cast was applied. Postoperative radiographs proved the success of reduction ( Figure 4).
The long arm cast was removed after 3 weeks and active motion was allowed thereafter. At the 6th postoperative week, the K-wire was removed operatively.
Two weeks after removal of the K-wire, radiographs revealed successful union of both bones ( Figure 5). His elbow flexion and extension and forearm pronation and supination were unrestricted (Figure 6).

Outcome and Follow-Up
The patient was discharged on postoperative day 1. He was followed for 8 weeks at 2 weeks' intervals.
At the 6th week K-wire was removed. He was examined on the 8th week, revealing unrestricted ROM of elbow and forearm ( Figure 6).

Discussion
This case highlights the importance of thorough clinical and radiological evaluation of pediatric patients with both bone forearm fractures. Failure to obtain and interpret goodquality radiographs properly is the most common problem of Monteggia fractures described in the literature [3]. Our case is another proof for this description. Adequate AP and lateral elbow radiographs must be taken in all pediatric forearm fractures of both bones. This case reports a fracture-dislocation pattern that was not previously described in the literature. According to the Bado classification, pediatric Monteggia fractures are classified by direction of the radial head dislocation and type of forearm fracture [2] (Table 1).
There are also Monteggia equivalent lesions, which describe fracture-dislocations equivalent to each subtype of the Bado classification. The direction of the radial head dislocation is the primary condition to classify equivalent injuries. Hence a forearm fracture of both bones is not always Case Reports in Orthopedics 5 Table 1: Lateral radial head dislocation with concomitant both-bone forearm fracture fits in the Bado classification as a type 3 equivalent lesion, which has never been described [2]. classified as type IV but rather in accordance to the direction of the radial head dislocation ( Table 1). The unusual fracturedislocation pattern in this case, namely, the lateral dislocation of the radial head and fracture of ulnar shaft, is a candidate to be named as a Monteggia type 3 equivalent lesion. Treatment is simple when diagnosed, but clinical consequences of delayed Monteggia fractures are dire as reported in the literature. Delayed diagnosis is still reported to constitute an important problem [4]. Undefined Monteggia lesions, like the one described in this case, might have contributed to missed diagnoses in the past. Therefore it is important for clinicians to critically evaluate and interpret radiographs in a patient with a forearm fracture of both bones.
In addition to the diagnostic features, we highlight a unique treatment method. Some authors believe that the purpose of treatment is to obtain an anatomically reduced radial head, which can often be accomplished with less than anatomic reduction of the ulna [3]. Others claim that the success of the treatment depends on an anatomic reduction and stabilization of the ulna [4]. In our case, although the ulna was reduced anatomically, the radial head was still dislocated laterally. We decided to insert an intramedullary nail in the radius and check the stability intraoperatively. This method provided an acceptable stabilization without the need for fixation of the ulna fracture.