An unusual Monteggia equivalent type 1 lesion: Diaphyseal ulna and radius fractures with a posterior elbow dislocation in a child.

In this report, we describe an extremely unusual Monteggia equivalent type 1 lesion in a 10-year-old boy following a fall from a height of 1 m. On the plain radiographs, our patient had a particular Monteggia equivalent type 1 injury associating a posterior elbow dislocation with diaphyseal radius and ulna fractures. The patient was treated by closed reduction technique. At six months of follow-up, the fractures were consolidated and the elbow was stable. To our knowledge, only 8 adult cases and one paediatric observation with similar lesions had been reported through medical literature. Therefore, the aim of our case report is to remind this rare entity and also to provide a comprehensive review of the literature related to this uncommon lesion.

Introduction

The classic Monteggia fracture consists of an ulnar fracture combined with a dislocation of the radial head. It was first described in 1814 by the Milanian Giovanni Batista Monteggia. These fractures were classified by Bado and divided into 4 types depending on the direction of dislocation of the radial head. The Monteggia fracture-dislocation is a rare lesion accounting for less than 1% of all paediatric elbow dislocations.1, 2 On the other hand, a so-called Monteggia equivalent lesions were described as special forms by Bado. These lesions are even rarer among children than the Monteggia fracture.1, 2 Indeed, their physiopathological and therapeutic characteristics are far from being codified. Here, we report a very rare Monteggia equivalent type 1 lesion associating a posterior elbow dislocation with a diaphyseal radius and ulna fractures in a 10-year-old boy. Therefore, the aim of our case report is to remind this rare entity and also to provide a comprehensive review of the literature related to this uncommon lesion.

Case report

A 10-year-old boy, right hand dominant, presented to the emergency department for a closed trauma of his right upper limb. He had sustained injury due to a fall from a height of 1 m with reception on the palm of his right hand. The physical examination, at admission, revealed a swollen elbow with loss of anatomical reference marks. The forearm was deformed. Clinical examination did not reveal any open wound or neurovascular abnormality. Plain radiographs showed diaphyseal fractures of radius and ulna along with posterior dislocation of right elbow (Fig. 1). The fracture was manipulated under general anaesthesia: the posterior elbow dislocation was reduced using longitudinal traction and elbow flexion. Fractures of the forearm were reduced and treated orthopedically with a long arm cast (Fig. 2). Weekly radiographs showed maintenance of reduction of injuries. After 8 weeks the cast was removed. At this time radiographic union had occurred. At six months of follow-up, the fractures were consolidated and the elbow was stable, painless with complete mobility (Fig. 3).

Fig. 1

Posterolateral elbow dislocation with ipsilateral fracture of both forearm bones.

Fig. 2

Plain radiographs after elbow reduction and forearm reduction and plaster immobilisation.

Fig. 3

Healing attained by follow-up at 6 months post-fracture.

Discussion

Fracture-dislocation of Monteggia is defined as a fracture of the ulna associated with a dislocation of the radial head. This lesion is rare among children representing only 0.4% of forearm fractures in childhood.1, 2 Bado, in 1967, classified this lesion in adults into four types according to the direction of dislocation of the radial head and angulation of the ulna. He also described two Monteggia equivalent injuries. Thereafter, type 3 and 4 Monteggia equivalent lesions were described based on the lesion mechanism.3, 4 Moreover, the Monteggia type 1 equivalent injuries have as a mechanism of lesion in pronation of the forearm.3, 5 In adult, the most common Monteggia type 1 equivalent injury is fracture of the ulnar diaphysis and fracture of the neck of the radius without dislocation of the radial head. In children, the relative laxity of the annular ligament makes this type 1 equivalent lesion extremely rare. In our case, we described a very particular type 1 Monteggia equivalent associating posterior dislocation of the elbow with fractures of the two bones of the forearm. We have done an extensive research for similar injuries through English medical literature. Only a limited number of similar injuries have been reported so far. Indeed, 9 cases of similar lesions were described in adults.3, 4, 5, 6, 7, 8 In the literature, this unusual lesion has been reported, in a child, only in one occasion reported by Frazier et al., in 1991. It was about a 7-year-old boy with anteriorly angulated diaphyseal ulna fracture and a proximal third radius fracture with a posterior elbow dislocation, as well as our patient. In those two paediatric cases, the patient was aged between 7 and 13 years. In fact, Frazier et al. suggested that during this period of age a change in physiology occurred. Their hypothesis was that the child goes from a relatively greater ligament to bone strength in a Monteggia fracture to a stronger bone profile in an elbow dislocation. Concerning the treatment, this particular lesion had an excellent results with only closed reduction technique which was used both in our case and in the observation of Frazier et al. in which the authors reported 2 years of follow up and the patient exhibited compete union with excellent alignment. On the other hand, in the adults' cases the treatment consisted in closed reduction of the elbow and open reduction and internal fixation of the forearm fractures. Through literature, this particular lesion seemed to have a better prognosis than the others types of Monteggia type 1 equivalent injuries both in children and in adults.8, 9 In fact, all the authors have reported good outcomes after treatment as well as in our case.

In conclusion, the Monteggia equivalent type 1 lesion associating a posterior dislocation of the elbow with diaphyseal fractures of the two bones of the forearm is an exceptional entity. The two lesions occur separately. In order to prevent missing any uncommon fractures, detailed evaluation of these injuries is needed. The radiographs should include the elbow and the wrist joints. The management must be rigorous in order to preserve the prognosis of limb.