Syndesmosis

What is syndesmosis and why talk about it ? 

Syndesmosis injuries are quite common, accounting for up to 18% of ankle sprains, and their incidence increases in the context of sporting activity (1). A syndesmotic injury can occur after ankle trauma, with or without a fracture of the bony part, often following a consistent external rotation injury mechanism. A thorough history and physical examination are of paramount importance for optimal management in care and for a return to the field as soon as possible as these injuries are often misdiagnosed as a stable high ankle sprain. This misdiagnosis of severity can lead to increased morbidity, slower rehabilitation and arthritic changes later in life (2).

Anatomically, what does this represent ?

The syndesmotic joint is formed by two bones and four ligaments. The distal tibia and fibula form the bony part of the syndesmosis and are connected by the distal anterior tibiofibular ligament, the distal posterior tibiofibular ligament, the transverse ligament and the interosseous ligament (3). 

How is it tested ?

In a syndesmosis injury, if the talus moves 1 mm laterally, the contact area of the tibiotalar joint decreases by 42%. This leads to early osteoarthritis of the tibiotalar joint. It is therefore important to check via X-ray, CT scan (or MRI if possible), after a fracture to ensure that the bones are correctly aligned with each other (4).

Several tests and manipulations are necessary to orient the diagnosis of a syndesmosis lesion:

• Palpation of the anterior inferior tibiofibular ligament that is tender or painful

• The squeeze test : compression of the tibio-fibula along the entire length of the leg, starting from the proximal to the distal part.  

• The Cotton Test : transverse translation of the talus in the mortise (between the 2 malleoli). Positive in case of pain, indicating deltoid ligament damage associated with syndesmosis damage. 
• Dorsiflexion-compression test : patient in bipodal support, the latter flexes the knees to induce a dorsiflexion of the ankle which will be painful. When the practitioner comes to compress mediolaterally the ankle ➔ the pain decreases. 

• External rotation test : passively induce external rotation of the ankle by stabilising the patient’s leg. 
  Note that it is essential to take into account the precise location of the pain during the tests 

On the other hand, radiographic images are requested with 3 incidences:

• Front
• Profile,
• and a view of the mortise (20° medial rotation).
  

X-rays are requested in case of suspected fracture, and in particular an associated fracture of the diaphysis or neck of the fibula (Maisonneuve fracture).

Syndesmosis involvement should be suspected on the front and mortise views based on three criteria:

• an enlargement of the tibio-fibular space (> 6 mm on a frontal view),
• an increase in the medial clear space (> 4 mm on a mortise view)
• reduction or disappearance of the tibio-fibular overlap (< 5 mm on a frontal view or < 1 mm on a mortise view) 

What treatment and rehabilitation ?

There are two main ways of treating this type of injury. If the injury is classified as stable, then conservative treatment will be provided by a physiotherapist. However, unstable injuries must be treated surgically. This involves stabilising the syndesmosis with a trans-syndesmotic screw or cable fixation (1). It is essential for the surgeon to restore good alignment and a correct tibia-fibula interval in order to be able to carry out quality rehabilitation afterwards. However, surgical techniques for syndesmosis can sometimes be difficult, such as those reported in a study of reoperations within the first week, which showed that 59% were due to misplaced syndesmosis screws postoperatively. New techniques of dynamic fixation of the syndesmosis using suture buttons may have advantages over malrotation of the fibula. Direct fixation of the posterior malleolus may theoretically reduce the need for syndesmosis fixation, but the complications associated with this much more extensive procedure need to be assessed before being recommended (5). Thus, research must continue in order to propose operations that are less aggressive to the fragility of the joint and its stability in the coming years. 

The aim of rehabilitation is to enable patients to return to their pre-injury activities as quickly and safely as possible. Protocols focus first on swelling control and recovery from surgery and then progress to restoration of motion, early protected weight-bearing, restoration of strength, and ultimately functional progression to desired activities.

• Phase I : focuses on pain control, reduction of inflammation and restoration of normal joint range of motion. Rehabilitation also recommends progressive loading and strengthening when 90-100% of pre-injury range of motion is recovered (within 6 weeks as recovery is more difficult after this time). Before, during or after the sessions, cardiovascular work on a bicycle (with or without the walking boot) is also recommended to activate the blood circulation of the whole body.
  
• Phase II : focuses on the flexibility of the foot and ankle and on functional strengthening. Thus, varied proprioceptive work focused on functional strengthening should be implemented as soon as possible, taking into account the patient’s feelings. 
  
• Phase III : emphasises the complete return to the functional activity prior to the injury, in particular by incorporating exercises with balls, on varied terrain, to lead to a reathletisation phase. 
  The most important concept to keep in mind in all rehabilitations is the progressiveness and adaptation of exercises to the patient’s progress. 

After the initial treatment, the patient can expect a recovery period of 2-6 months before returning to pre-injury activities (1). This injury can take a long time to heal but it is important to treat it well so that it does not develop into chronic ankle instability. Moreover, this delay is often due to a delay in diagnosis, which can only be detrimental to the patient’s recovery. 

In addition, some scientists believe that during the season following the syndesmosis injury it may be advisable to wear a soft brace during matches or training sessions in order to fix the repair of the ankle. 

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