Subtalar dislocation

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Key words:
Subtalar
dislocation
talar dislocations
subtalar dislocation and sports


Definition/Description


Subtalar dislocation is a rare ankle injury accounting for approximately 1% of all dislocations. This injury occurs due to high-energy trauma [1]. A subtalar dislocation occurs through the disruption of 2 separate bony articulations, the talonavicular and talocalcaneal joints [2]. There are four types of subtalar dislocation: medial, lateral, anterior and posterior dislocations. Medial subtalar dislocations predominate, accounting for approximately 80% of reported dislocations. Less common are lateral dislocations (17%), posterior dislocations (2.5%), and anterior dislocations (1%)[3].


Clinically Relevant Anatomy


The subtalar joint is a synovial joint between the ‘facies articularis calcanea posterior’ of the talus and the ‘facies articularis talaris posterior’ of the calcaneus. The calcaneus does in- and eversion movements, of which the supination/pronation and abduction/adductioncomponents are the most important ones in a closed chain. In supination, the posterior part of the calcaneus will slide laterally, in pronation it will slide to the medial side [4]. The most important ligament of the subtalar joint is the interosseus talocalcaneal ligament, there are four other weaker connections between talus and calcaneus which are: the anterior talocalcaneal ligament, the posterior talocalcaneal ligament, lateral talocalcaneal ligament and the medial talocalcaneal ligament [5].


Epidemiology/Etiology


When we take a closer look at subtalar dislocations these traumas are usually seen when a person suffered a high-energy trauma i.e., when falling from a height (20%) or in case of motor accidents (48%) [6]. In sports most subtalar dislocations occur during basketball games, for that reason subtalar dislocation is also called a ‘basketball foot’[7]. A dislocation of the subtalar joint occurs when a plantar-flexed foot suffers a trauma. If the foot lands on the ground while in inversion or eversion, this respectively results in a medial (80%) or a lateral (17%) subtalar dislocation. Anterior (1%) and posterior (2.5%) dislocations have also been examined and described but they are extremely rare, considering the percentages [6].


Diagnostic procedures


Patients with a subtalar dislocation obviously have a lot of pain and there is no possibility to bear weight on the affected foot. You can clearly see a deformity to the extremity. The talar head can stick out prominently and the talonavicular and medial subtalar joints are very tender and painful to palpate. But a CT-scan always needs to be done to be completely sure of the diagnosis or to see what type of dislocation it is [8]. In 88% of all patients an associated foot and ankle injury occurs. Ankle, talar, calcaneal and navicular bones run the highest risk to be fractured. The cuneiforms, cuboid and metatarsals are sometimes injured, the toes on the other hand never get affected. All parts of the foot that could be damaged due to a subtalar dislocation have to be examined by use of radiographic material [6].


Medical management


Subtalar dislocations get reduced, normally under general anesthesia by manual pressure and traction on the ‘caput tali’. Talus relocation is performed with the knee flexed to reduce tension of the soleus and gastrocnemius muscle. Subsequently, the subtalar instability is evaluated by use of fluoroscopy. When there are no signs of instability, the ankle will be immobilized in a below-the-knee back slab (= a plaster that not completely surrounds the limb, it protects the injured area and allows it to swell), which is not able to bear weight, followed by administration of analgesia and foot elevation. A CT-scan is performed to evaluate the anatomic reduction and to see if there are any fractures. Ligamentary laesions are sutured [8,9].


Physical therapy


Because of the incidence, almost every study about subtalar dislocations includes patients with a medial dislocation. Recent studies evaluated the influence of physical therapy on dislocations, the outcome was that ‘early mobilization after an uncomplicated medial subtalar dislocation provides successful functional results’. In case of open dislocations there is a washout(=the wound gets left open under chemoprophylaxis and is secondary closed 3days later when the cast is applied) before the reduction takes place. Physiotherapy can be started when the swelling goes down and when non-weight-bearing mobilization is allowed, 3-4 days after reduction. The mean purpose of physical therapy is to regain mobility in the ankle joints. By the beginning of the third week, the physiotherapist can start active range of motion exercises for the ankle, foot and muscle-strengthening exercises. After the third week, patients can start with partial-weight-bearing exercises and they progress to full weight bearing at week five. The exercises for full weight bearing should be performed using a below the knee functional ankle brace. This brace helps with plantar- and dorsiflexion but inhibits inversion and eversion movements. This experiment concludes that all patients who had gone through this therapy regained a normal ankle ROM (evaluated by agoniometer) The mean percentage of ankle ROM between the injured and healthy lower limb was 92.5% which was considered very satisfactory by both physiotherapists and patients. The mean AOFAS ankle-hindfoot scale (American Orthopaedic Foot and Ankle Society) score was 90.75 points (range: 82-97). AOFAS ankle-hindfoot scale scores pain, function and alignment. 3 years post-reductive, no radiographic evidence of arthritis or avascular necrosis of the talus was detected. Two patients complained of mild pain of the hindfoot. All patients returned to daily routine activities in about 2 months post injury [9].


References:

1. Jason Bryant – Joel T. Levis, Subtalar dislocation. Western Journal of Emergency Medicine 2009, 10 (2). (Level of evidence 4).


2. Joel Horning – DiPreta, Subtalar dislocation. Orthopedics 2009; 32(12);904. (Level of evidence 3A )


3. DeLee, Curtis. Subtalar dislocation of the foot. The journal of Bone and Joint Surgery. 1982;64(3):433-437 ( Level of evidence 3B).


4. Filip Staes – Simon Brumagne, Kinesitherapeutisch onderzoek van onderste extremiteiten en lumbale wervelkolom. Acco 2009, 1e druk, 76-77.


5. Bohn – Stafleu – van Loghum, Anatomische Atlas. Houten 2009, 400-411.


6. Bibbo et al., Injury characteristics and the clinical outcome of subtalar dislocations: a clinical and radiographic analysis of 25 cases. Foot Ankle Int. 2003. 24(2):158-63. (Level of evidence 2A)


7. O. Sahap Atik. – Hakan Dur, Unusual tennis injuries: boxer’s fracture and medial subtalar dislocation: report of two cases, Eklem Hastalik Cerrahisi. 22(3):180-2. (December 2011) (Level of evidence 4)


8. Elias Fotiadis et al., Closed subtalar dislocation with non-displaced fractures of talus and navicular: a case report and review of the literature. Cases J. 2009; 2: 8793. (Level of evidence 4)


9. Nikolaos G. Lasaniano et al., Early mobilization after uncomplicated medial subtalar dislocation provides successful functional results. The Author(s) (2010) 12:37-43. (Level of evidence 3B)