Subtalar Dislocation

Original Editor - Pieter Piron Top Contributors - Khloud Shreif, Kim Jackson, Aimee Tow, Abbey Wright, Pieter Piron, Fasuba Ayobami, Wanda van Niekerk and Amanda Ager

Definition/Description

Subtalar dislocation occurs through the disruption of 2 separate bony articulations, the talonavicular and talocalcaneal joints. Subtalar dislocations are a rare ankle injury accounting for about 1%-2% of all joint dislocations. This injury occurs due to high-energy trauma, including falls, motor vehicle crashes, and sports injuries. 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%).

Clinically Relevant Anatomy

The subtalar joint is a synovial joint betweek the talus and calcaneus. The facets of the talus and calcaneus alternate concave and convex. They are surrounded by strong ligaments that make this joint relatively stable.

Subtalar joint motion is complex because the axis or rotation is at an angle. Subtalar joint motion in open chain combines dorsiflexion/abduction/eversion and plantarflexion/adduction/inversion. In closed chain, these motions are referred to as pronation and supination.

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 .

Epidemiology/Etiology

Subtalar dislocations are usually seen when a person suffers a high-energy trauma i.e., when falling from a height (20%) or in case of motor crash (48%). A dislocation of the subtalar joint usually occurs during plantar flexion and the injury is usually a closed injury. 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.

Diagnostic Procedures

Patients with a subtalar dislocation have a lot of pain and are unable to bear weight on the affected foot. A clear deformity of the ankle can be seen. The talar head can stick out prominently and the talonavicular and medial subtalar joints are very tender and painful to palpate. A CT scan is usually performed to determine the type of injury. In 88% of all patients an associated foot and ankle injury also occurs. Ankle, talar, calcaneal and navicular bones run the highest risk of being fractured. The cuneiforms, cuboid and metatarsals are sometimes injured. All parts of the foot that could be damaged due to a subtalar dislocation have to be examined radiographically.

Medical Management

Subtalar dislocations get reduced, normally under general anesthesia by manual pressure and traction. 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. Pure dislocations (those without concomitant fractures) usually have a more favorable prognosis. There is not consensus on how or how long the ankle should be immobilized after dislocation. Studies show a range if immobilization times from 3 to 8 weeks depending on concomitant injuries.

Physical Therapy Implications

Because of the rate of occurance, most studies of subtalar dislocations include patients with a medial dislocation.

A recent study shows early mobilization after uncomplicated medial subtalar dislocation assist patients in returning to daily function in 2 months.

Physical therapy can be started when non-weight-bearing mobilization is allowed, 3-4 days after reduction. The purpose of physical therapy at this time is to reduce swelling and gain range of motion.

According to this study, week 3 after injury active range of motion exercises for the ankle, foot and muscle-strengthening exercises were started. After the third week, patients started with partial-weight-bearing exercises and progressed to full weight bearing at week five. The exercises for full weight bearing were performed using a below the knee functional ankle brace. This brace allowed plantar- and dorsiflexion but inhibited inversion and eversion movements.

This study concluded that all patients who had gone through this therapy regained a normal ankle ROM (evaluated by a goniometer) 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.