Antero-lateral subtalar dislocation
Article Outline
Abstract
Subtalar dislocation is the simultaneous dislocation of the distal articulations of the talus at both the talocalcaneal and talonavicular joints. It can occur in any direction and always produce significant deformity. Most common is the medial dislocation. Less common presentations are lateral, anterior and posterior dislocations. These dislocations are associated with osteochondral fractures. Closed reduction and immobilisation remains the mainstay of treatment. Proper radiographs and CT scan confirm the post-reduction alignment stability of subtalar joints and intraarticular fracture fragments. We report a case of antero-lateral subtalar dislocation with no osteochondral fracture fragments in a 28-year-old man.
Keywords: Antero-lateral, Subtalar, Dislocation, Rare, Diagnosis
Subtalar dislocations are rare in routine orthopedic practice. Many of these dislocations results from high-energy injuries such as a fall from a height, athletic injuries or a motor vehicle accident. Inversion or eversion force is dissipated through the weak talonavicular and talocalcaneal ligaments, which eventually results in subtalar dislocation.
The head of the talus is found medially and the rest of the foot is dislocated laterally in lateral subtalar dislocation. The head of the talus is found laterally and the rest of the foot medially in medial subtalar dislocation. Medial dislocation has been referred to as an “acquired clubfoot”, while the lateral injury is described as an “acquired flatfoot”.
We present a case of an adult with antero-lateral subtalar dislocation following a fall.
1. Case report
A 28-year-old man who sustained a fall from stairs came to our emergency department with pain and swelling of the right foot. The foot was diffusely swollen with minimal laceration and tenting of the skin over the prominent talar head, which was, felt dorso-medially. The rest of the foot was found dislocated laterally (Figs. 1 and 2). Posterior tibial artery and dorsalis pedis artery pulses were not felt due to massive soft tissue distortion. Radiograph of the right foot showed anterior and lateral subtalar dislocation (Figs. 3 and 4). Doppler ultrasound showed normal arterial flow in both posterior tibial and dorsal pedis arteries.
Figs. 1 and 2.
The foot was diffusely swollen with minimal laceration and tenting of the skin over the prominent talar head, which was, felt dorso-medially. The rest of the foot was found dislocated laterally.
Figs. 3 and 4.
showed the dislocation of the talonavicular and subtalar joints. Head of the talus was seen lying antero-medially. Normal alignment of calcaneocuboid joint can also be appreciated.
Closed reduction was done under spinal anesthesia. Firm manual foot traction with counter-traction on the leg combined with direct digital pressure over the head of talus aided a smooth reduction, which was associated with an audible clunk. Post-reduction radiographs showed normal and stable alignment of the subtalar and talonavicular joints with absence of osteochondral fractures (Figs. 5 and 6). CT scan confirmed the absence of osteochondral fractures and the stability of the subtalar joints. The patient was immobilized in a short-leg posterior plaster splint for 4 weeks. A vigorous active exercise program with progressive weight bearing were active exercises to regain subtalar and midtarsal joint motion was followed by immobilization. Two years after the injury, the patient had a stable, relatively good functional foot, with minimal pain on walking on uneven ground.
Figs. 5 and 6.
Post-reduction radiographs showed normal and stable alignment of subtalar and talonavicular joints with absence of osteochondral fractures.
2. Discussion
Subtalar dislocation by definition has a normal tibiotalar joint. Most dislocations occur in males (6:1) of early age. Subtalar dislocation can occur in any direction and always produces significant deformity. Most commonly (80–85%), the foot is displaced medially with the calcaneus lying medially, the head of the talus prominent dorsolaterally, and the navicular medial and sometimes dorsal to the talar head and neck [1], [2], [3]. Less commonly (15–20%), lateral dislocation occurs.
Inversion of the foot results in a medial subtalar dislocation, while eversion produces a lateral dislocation. The strong calcaneonavicular ligament resists disruption, and the inversion or eversion force is dissipated through the weaker talonavicular and talocalcaneal ligaments, disrupting these two joints and allowing displacement of the calcaneus, navicular and all distal bones of the foot as a unit, either medially or laterally [2], [3].
The sustentaculum tali acts as a fulcrum about which the foot rotates to lever apart the talus and calcaneus in medial subtalar dislocation. The foot pivots about the anterior process of the calcaneus, again causing the talus and calcaneus to separate in lateral subtalar dislocation [1], [2], [3], [4].
Rare cases of anterior [5] and posterior [1] displacement of the foot after subtalar dislocation have also been reported. It is important to distinguish between medial or lateral subtalar dislocations because the method of reduction is different and the long-term prognosis appears to be worse with the lateral dislocation.
Between 10% and 40% of subtalar dislocations are open [6]. Open injuries tend to occur more commonly with the lateral subtalar dislocation pattern and probably as the result of a more violent injury [6]. Long term follow up demonstrates very poor results following open subtalar dislocations.
The keystone of treatment for all subtalar dislocations is prompt and gentle reduction under general or spinal anesthesia [7]. All open injuries must be thoroughly debrided at the time of reduction, and the wound should be left open, with delayed primary closure anticipated in 3–5 days. Because of the high incidence of associated articular fracture and associate poor prognosis, CT scan of the foot and ankle should be obtained after reduction and splinting.
Simple dislocations that are reduced readily by closed reduction and do not have an associated fracture do very well [1]. In approximately 10% of medial subtalar dislocations and 15–20% of lateral dislocations, closed reduction cannot be achieved [3], [8]. Soft tissue interposition and bony block have been identified as factors preventing closed reduction. Another common obstruction to closed reduction in medial dislocations is an impaction fracture of the articular surface of talus and navicular [7]. The most common obstruction to closed reduction in lateral subtalar dislocation is the interposed tibialis posterior tendon [8].
Open reduction is done for irreducible medial, lateral subtalar dislocations and osteochondral fracture fragments which blocks closed reduction. Any small, loose articular fracture fragments should be removed, while large intra-articular fractures should be reduced and fixed with Kirschner wires or small screws to restore joint stability and congruity [9].
The only consistent complication in simple uncomplicated dislocations is limitation of subtalar joint motion, with the occasional associated symptoms of difficulty in walking on uneven ground and pain in the foot with weather change [2], [7]. Lancaster et al. noted a poorer prognosis when there were associated factors such as soft tissue injury, open contaminated injuries, extra-articular fracture, intra-articular fracture, infections, lateral subtalar dislocations, neglected subtalar dislocations and osteonecrosis [10].
Our patient who had sustained a fall from stairs came with a diffusely swollen foot with the head of talus felt dorso-medially and the rest of the foot dislocated laterally as a unit. Radiographs confirmed the antero-lateral subtalar dislocation. There was no associated osteochondral fracture. Simple closed reduction was successful. Our literature review showed no reports of isolated antero-lateral subtalar dislocation.
We emphasize the importance of proper diagnosis and timely management of dislocations around subtalar joint, as these always produces significant deformity and joint stiffness. Antero-lateral subtalar dislocation is one such type which is not mentioned in literature should be carefully treated and always a high index of suspicion should be kept about associated osteochondral fractures. CT scan should be done after reduction to look for the intra-articular fractures of the subtalar joint. Open reduction is done for irreducible dislocations and fixations done in large displaced articular fragments producing subtalar joint incongruity.
Conflict of interest
No financial and personal relationships with other people or organizations that could inappropriately influence (bias) this work.
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PII: S1268-7731(07)00072-0
doi:10.1016/j.fas.2007.08.002
© 2007 European Foot and Ankle Society. Published by Elsevier Inc. All rights reserved.
