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ORIGINAL ARTICLE

Antero-Medial Subtalar Dislocation- A Case Report

J. Terrence Jose Jerome, Mathew Varghese, Balu Sankaran,

St Stephen’s Hospital, Delhi, India

Address for Correspondence

Dr. J.Terrence Jose Jerome,
Department of Orthopedics,
St Stephen’s Hospital,
Tiz Hazari,
Delhi.54, India.
Phone
: +911-9868086916
Email
: terrencejose@gmail.com
Fax:+911-23932412

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 immobilsation remains the mainstay of treatment. Proper radiographs and CT scan confirms the post reduction alignment stability of subtalar joints and intraarticular fracture fragments. We report a case of antero-medial subtalar dislocation with no osteochondral fracture fragments in a 25-year-old man.

J.Orthopaedics 2006;3(3)e3

Introduction:

Subtalar dislocations are found rare in routine orthopedic practice. Many of these dislocations results from high-energy injuries such as 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 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-medial subtalar dislocation following a fall.

Case report

A 25-year-old man who sustained a fall from stairs came to our emergency department with pain, swelling right foot. The foot was diffusely swollen with minimal laceration and tenting of the skin over the prominent talar head, which was, felt dorso laterally. The rest of the foot was found dislocated medially. Posterior tibial artery and dorsalis pedis artery pulse was not felt due to massive soft tissue distortion. Radiograph of the right foot showed anterior and medial subtalar dislocation Fig (1). Doppler ultrasound showed normal arterial flow in both posterior tibial and dorsal pedis arteries.

Figure (1) showed the dislocation of the talo-navicular and subtalar joints. Head of the talus was seen lying antero-laterally. Normal alignment of calcaneo-cuboid 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 in smooth reduction, which was associated with an audible clunk. Post reduction radiographs showed normal and stable alignment of subtalar and talo-navicular joints with absence of osteochondral fractures. CT scan confirmed the absence of osteochondral fractures and the stability of the subtalar joints. Patient was immobilized in a short-leg posterior plaster splint for 4 weeks. Vigorous, active exercise program, progressive weight bearing, active range of motion exercises to regain subtalar and midtarsal joint motion followed immobilization. One year after the injury, the patient had a stable, relatively good functional foot, with minimal pain on walking on uneven ground.

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% to 85%), the foot is displaced medially with the calcaneus lying medially, the head of the talus prominent dorsolaterally, and the navicluar medial and sometimes dorsal to the talar head and neck1,2,3. Less commonly (15% to 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 laterally2,3.

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 dislocation1,2,3,4.

Rare cases of anterior5 and posterior1 displacement of the foot after subtalar dislocation have also been reported. It is important to distinguish the 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 open6. Open injuries tend to occur more commonly with the lateral subtalar dislocation pattern and probably as the result of a more violent injury6. Long terms follow demonstrated very poor results following open subtalar dislocations.

The keystone of treatment for all subtalar dislocations is prompt and gentle reduction under general or spinal anesthesia7. 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 to 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 dislocation that are reduced readily by closed reduction and do not have associated fracture do very well.1 In approximately 10% of medial subtalar dislocations and 15% to 20% of lateral dislocations, closed reduction cannot be achieved3,8. Soft tissue interposition and bony blocks 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 navicluar7. 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 congruity9.

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 change2,7. Lancaster and his co-workers noted a poorer prognosis when there were associated injuries such as soft tissue injury, open contaminated injuries, extra-articular fracture, intra-articular fracture, infections, lateral subtalar dislocations, neglected subtalar dislocations and osteonecrosis10.

Our patient who had sustained a fall from stairs came with diffusely swollen foot with the head of talus felt dorso-laterally and the rest of the foot dislocated medially as a unit. Radiographs confirmed the antero-medial subtalar dislocation. There was no associated osteochondral fracture. Simple closed reduction was successful. Our literature review showed no reports of isolated antero-medial 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-medial subtalar dislocation is one such type which is no where 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.

                                                                    

Reference :

  1. DeLee JD, Curtis R. Subtalar dislocation of the foot. J Bone Joint Surg 1982; 64A:433-437.
  2. Grantham SA. Medial Subtalar dislocation: five cases with a common etiology. J Trauma 1964; 4:845-849.
  3. Heppenstall RB, Farahvar H, Balderston R, et al. Evaluation and management of subtalar dislocations. J Trauma 1980; 20: 494-497.
  4. Monson St, Ryan JR. Subtalar dislocation. J Bone Joint Surg 1981; 63A:1156-1158.
  5. Inokuchi S, Hashimoto T, Usami N. Anterior subtalar dislocation: case report. J Orthop Trauma 1997; 11(3): 235-237.
  6. Golner JL, poletti SC, Gates HS III et al. Severe open subtalar dislocations: long-term results. J Bone Joint Surg 1995; 77A (7):1075-1079.
  7. Bohay DR, Manoli A II. Subtalar dislocations. Foot Ankle Int 1995;16(12): 803-808.
  8. Leitner B. Obstacles to reduction I subtalar dislocations. J Bone Joint Surg 1954; 36A:299-306.
  9. Naranja RA, Monaghan BA, Okereke E et al. Open medial subtalar dislocation associated with posterior process fracture of the talus. J Orthop Trauma 1996; 10(2): 142-144.
  10. Lancaster S, Horowitz M, Alonso J. Subtalar dislocations: a prognosticating classification. Orthopedics 1985; 8: 1234-1240.

This is a peer reviewed paper 

Please cite as : J. Terrence Jose Jerome: Antero-Medial Subtalar Dislocation- A Case Report

J.Orthopaedics 2006;3(3)e3

URL: http://www.jortho.org/2006/3/3/e3

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