Pure Talocrural Dislocation without Associated Malleolar Fracture

Pure talocrural dislocation is an uncommon injury of the ankle. Malleolar fracture is usually associated. We report two cases of pure talocrural dislocation, to describe its therapeutic and prognostic clinical aspects through a review of the literature.


Introduction
Pure talocrural dislocation is the dislocation of the ankle. The talocalcaneal block is expelled out of the mortise which is intact both with regard to malleoli and syndesmosis [1].
It is a simple dislocation compared to subtalar dislocation, which is a double dislocation, and enucleation of the talus which is a triple dislocation. This is a very rare lesion that occurs in a context of violent trauma. Historically, the first case was published in 1912 by Auvray [2]. It is an emergency whose management, apart from complications (cutaneous opening, vascular and nerve lesions), is most often orthopedic: reduction under general anesthesia followed by a restraint by plaster cast.
Pure talocrural dislocation can compromise the functional development of the ankle due to late complications such as stiffness of the ankle, osteoarthritis or necrosis of the talus.
The goal of this work was to report two cases of pure talocrural dislocation, to describe its therapeutic and prognostic clinical aspects through a review of the literature. The palpation and the mobilization of the ankle caused a sharp pain. The X-ray of the ankle showed pure posterior talocrural dislocation without associated bone lesion ( Figure 1).
The reduction was carried out in an emergency by maneuvering a boot jack.
The control X-ray confirmed the reduction of dislocation ( Figure 2). The arterial duplex scan of the limb was normal. The restraint has been ensured by a plastered boot for 6 weeks. Rehabilitation of the ankle has been started as soon as the cast was removed.
After 2 years of hindsight, the patient had no pain, and he had resumed his sporting and professional activities. The functional results (Figure 3), judged on the Gay and Evrard score (Table 1), were excellent with a score of 15 points. The X-rays of the ankle were normal.

 Epidemiology
We have only found two cases over a period of 15 years.
Pure talocrural dislocation is exceptional [3] [4]. The first case documented by X-ray was described in 1913 by Peraire [1]. The work reported in the literature on this lesion is few [5]. Until 1995, only 73 cases were reported [6]. Most studies are based on clinical facts that rarely exceed 2 cases.
Only two series of more than 10 cases [1] [7] have been reported.
The scarcity of this lesion is due to the mechanical stability of the tibiofibular mortise and the resistance of the collateral ligaments, which are as strong as the malleolus, hence the high frequency of the fractures [8].

 Mechanisms and circumstances of occurrence
For the cases of our two patients, these were respectively real-life accidents of Open Journal of Orthopedics We had two posterior dislocations. In both cases, the mechanism was a misstep associated with inversion of the foot.
According to Fernandes [13], the mechanism of the lesion usually consists of a high energy trauma, which produces sufficient anteroposterior force applied to the foot in maximal plantar flexion resulting in a posterior dislocation of the ankle. The Plantar flexion was considered to be the unstable position of the talocrural joint because the narrow part of the body of the talus lies in the mortise, allowing dislocation.
Fahey and Murphy [5] classified this lesion into five types according to the direction of dislocation: anterior, posterior, medial, lateral and superior. They add the combined forms. The posteromedial variety is the most common [ [24].
Lower tibiofibular ligaments are intact in posterior dislocations [18] [20].  Treatment The management of pure talocrural dislocation should not be delayed because it is an extreme emergency. Closed dislocations must be treated orthopedically. The reduction is done by maneuvering a boot jack in the posterior varieties, under general anesthesia, knee flexed to release the triceps sural muscle [10] [12]. Most authors recommend emergency reduction followed by plaster cast restraint whether the dislocation is open or closed [7] [25]. Orthopaedic reduction was performed without anaesthesia in both our patients. Indeed our working conditions in our hospitals in sub-Saharan Africa do not often allow us to have a fast general anaesthesia in our patients.
This immobilization must last 6 to 8 weeks [1] [15] [16]. Open dislocations require trimming with drainage, and repair of capsular, neurovascular and musculotendinous lesions. The repair of collateral ligaments is controversial. Finkmeier [26]  Other late complications are reported in the literature such as ankle osteoarthritis [6], avascular necrosis of the talus [7] and residual ligament laxity [18].

Conclusion
The talocrural dislocation without malleolar fracture is an exceptional lesion. It occurs in a context of high energy trauma. Its treatment is most often orthopedic with excellent functional results.