A syndesmotic ankle sprain is an injury to one or more of the ligaments comprising the distal tibiofibular syndesmosis; it is often referred to as a “high ankle sprain.” Compared with the more common lateral ankle sprain, the high ankle sprain causes pain more proximally, just above the ankle joint, and is associated more often with significant morbidity. Diagnosis can be difficult and clinicians should consider the possibility of syndesmotic injury in athletes with pain or injury around the ankle or lower leg. Treatment too is different from typical ankle sprains and surgery may be necessary, making recognition important for optimal recovery.High ankle sprains typically occur during high-intensity athletic activities such as competitive American football, soccer (football), lacrosse, hockey, and other contact or collision sports, and downhill skiing. An external rotation force applied to a dorsiflexed ankle is the most common mechanism. This can happen when the leg is rotated forcefully against a planted foot or toe. Most such injuries occur during contact with other athletes either when the athlete is standing and the foot is forced into dorsiflexion and external rotation , or when the athlete is prone on the ground and another athlete steps or lands on their posterior leg while the foot is externally rotated .
Definitions — There is heterogeneity in the orthopedic literature about the definition of injury grades for high ankle sprains . The author suggests the following classification scheme
- Grade 1 injury – Partial tearing of AITFL, with no diastasis on radiograph, computed tomography (CT), or magnetic resonance imaging (MRI); considered a stable injury.
- Grade 2 injury – Complete tear of AITFL and partial tear of IOM, without diastasis seen on radiograph, CT, or MRI; considered a latently unstable injury. Ultrasound or MRI may be needed in some cases for diagnosis and distinction from grade 1 and grade 3 injuries. Usually involves partial deltoid (medial) ankle ligament injury. Some have proposed subclassifying grade 2 injuries using a combination of MRI findings and clinical signs. Grade 2a injuries involve a ruptured AITFL but no concomitant ligamentous injury on MRI (other than the ATFL) and clinical stability. Grade 2b injuries involve a ruptured AITFL and concomitant injury to the deltoid ligament or PITFL on MRI and clinical signs of instability, such as a positive squeeze test and tenderness extending greater than 6 cm proximal to the ankle joint
- Grade 3 injury – Complete tear of AITFL and IOM plus partial or complete tear of PITFL, with diastasis on radiograph, CT, or MRI; considered an unstable injury. Usually involves concomitant fractures and complete deltoid ligament rupture
Overview — Grade 1 injuries are managed conservatively with immobilization for one to three weeks followed by gradual return to activity, while grade 2 and grade 3 injuries require evaluation for possible operative management.
Concomitant fractures — Syndesmotic injuries concurrent with ankle fractures should be splinted and referred urgently to an podiatric consultant. Syndesmotic instability is treated with reduction of the fibula and surgical fixation.
Syndesmotic injuries without fractures — All syndesmotic injuries should be treated initially with splinting and non-weight-bearing. Early treatment for injuries of all grades should include PRICE-M (protection, rest, ice, compression, elevation, and medication) for the first two to four days:
- Protection is achieved optimally with a posterior leg splint , as it prevents excessive dorsiflexion and is easier to don than a fracture boot, although a fracture boot may be used.
- Rest is achieved by non-weight-bearing using crutches.
- Ice – Cryotherapy applied as ice or cold water immersion is recommended for 15 to 20 minutes every two to three hours for the first 48 hours, or until swelling is improved – whichever comes first.
- Compression with an elastic bandage to minimize swelling should be applied early.
- Elevation – The injured ankle should be kept elevated above the level of the heart to further alleviate swelling.
- Medication – A short course of nonsteroidal antiinflammatory drugs (NSAIDs) and/or acetaminophen can be used for analgesia as needed.
High-grade syndesmotic injuries — Grade 2 and grade 3 syndesmotic injuries without fracture should be treated initially by referring to podiatrist for possible operative management . These injuries are uncommon without concomitant fracture, and research is extremely limited, but expert opinion strongly favors surgical treatment of grade 2 and grade 3 syndesmosis injuries. Some grade 2 injuries may be stable enough for conservative management , but we recommend that this determination be made only by clinicians skilled in the evaluation and treatment of such ankle injuries.