A syndesmosis is a slightly movable fibrous joint in which bones such as the tibia and fibula are joined together by connective tissue. Examples include the distal tibiofibular joint as well as the radioulnar joint. Injuries to the ankle syndesmosis are commonly known as a "high ankle sprain". Although the syndesmosis is a joint, in the literature the term syndesmotic injury is used to describe injury of the syndesmotic ligaments. It comes from the Greek σύν, syn (meaning "with") and δεσμός, desmos (meaning "a band"). Syndesmosis sprains have received increasing recognition during recent years because of a heightened awareness of the mechanism, symptoms, and signs of injury.
Diagnosis of a syndesmotic injury
Diagnosis of syndesmosis injuries by physical examination is often straightforward. Physical examination findings that are often positive include the squeeze test and the external rotation test. Patients with high-grade syndesmosis injuries often cannot perform a single-leg heel raise. Patients report pain over the anterior and often posterior distal fibular joint.
The severity of acute syndesmosis injury is rated from grade I to III by several authors. A grade I injury is a partial anteroinferior tibiofibular ligament tear, meaning the exorotation and squeeze tests are negative for this grade. Grade II injury is a complete anteroinferior tibiofibular ligament and inferior interossesus ligament tear, meaning that squeeze test and exorotation are positive. This results in the injury being stabilized with immobilization but not operatively stabilized. A grade III injury is a complete anteroinferior tibiofibular ligament tear including a (partial) interosseous ligament tear and deltoid ligament avulsion, meaning the joint is unstable and positive on the exorotation and squeeze tests. This grade requires operative stabilization. If the syndesmosis is torn apart as result of bone fracture, surgeons will sometimes fix the relevant bones together with a syndesmotic screw, temporarily replacing the syndesmosis, or with a tightrope fixation , which is called Syndesmosis Procedure. The screw inhibits normal movement of the bones and, thereby, the corresponding joint(s). When the natural articulation is healed, the screw may be removed. The tightrope fixation with elastic fiberwire suture on the other hand allows physiologic motion of the ankle and may be permanent.
- Dr. M. A. (Toby) Arnold; Deborah Bryce. "Arnold's Glossary of Anatomy". The University of Sydney.
- Jones, MH; Amendola, A. "Syndesmosis sprains of the ankle". Lippincott Williams & Wilkins, 2007, p.173-75.
- Johnson, Darren L, MD; Metzler, Adam V, MD. "Dynamically Unstable Syndesmosis Injuries". Slack Incorporated, 2013, p.209-11.
- Valkering, Kars P, MD; Vergroesen, Diederik, A, MD; Nolte, Peter A, MD, PhD. "Isolated Syndesmosis Ankle Injury". Slack Incorporated, 2012, p.e1705-10.