Ankle syndesmotic injuries are involved in 5-10 per cent of all ankle sprains and 23 per cent of ankle fractures. Despite this prevalence, there is a lot of debate regarding proper diagnosis and treatment of this complex injury.
The complexity of the injury to the syndesmosis lies in the anatomy. The convex distal fibula and concave distal, lateral tibia form a syndesmotic articulation and require specific congruency and mobility to accommodate the underlying talus. The fibula must be able to rotate, translate and migrate to allow for normal ankle movement. The syndesmotic articulation must also be stable, and thus comprises four distinct ligaments. The anterior inferior tibiofobular ligament and the deep posterior inferior tibiofibular ligament contribute the most to ankle stability, combining to provide 68 per cent of the stability to the joint.
Ankle sprains that involve a combination of hyperdorsiflexion and external rotation at the ankle are the most common that result in syndesmotic injury. The injury can involve only damage to the ligaments or combine ligamentous damage with fracture. Isolated syndesmotic injuries are often referred to as high ankle sprains and result in pain and ankle instability. Physical examination can be conducted at three to five days after injury with the patient adhering to rest, ice, compression and elevation (RICE) during this time.
Common evaluation stress tests including the squeeze test, the external rotation stress test or cross leg test are considered positive if pain decreases with compression. Physical examination can be conducted
at three to five days after injury with the patient adhering to rest, ice, compression and elevation (RICE) during this time. Radiographic, CT, and/or MRI can be further used to confirm syndesmotic injury including fracture as deemed necessary. The three common syndesmotic fracture injuries include Weber Type C fracture (pronation-external rotation), Weber Type B (supination- external rotation) and Maisonneuve fracture (involving proximal fibular fracture). A malleolar fracture can also result in syndesmotic injury, but this is much more difficult to diagnose unless done intraoperatively with the hook test or external rotation test under flouroscopy.
Traditionally all syndesmotic fractures are treated operatively with screw fixation being the gold-standard. Syndesmotic reduction becomes an important factor with all fixation procedures as malreduction is common and results in significantly worse functional outcomes. Malreduction typically takes place when the fibula is fixed in the wrong position. Malreduction rates decrease from 50 per cent to 15 per cent with direct visualization of the tibiofibular joint. If direct visualization is not possible with the surgical technique, intraoperative 3D imaging show promise in reducing malreduction rates as well.
A second factor of concern with fixation is the elimination of normal movement between the fibula and tibia that is essential for ankle mobility. Suture button fixation is a new technique that may eliminate the latter concern as it is not a rigid fixation like the screws. A recent systematic review showed that suture button fixation resulted in similar healing time to screw fixation, but the patients reported an earlier return to work and less frequent need for implant removal. Restoring normal biomechanics to the ankle joint whether by use of suture button fixation or removal of screw fixation after healing can lead to improved syndesmotic reduction and improved functional outcomes.