Syndesmotic Ankle Injury (High Ankle Sprain)

Disclaimer: Please read the Disclaimer at the bottom of this page.
Copyright © Educom Pty Ltd: All material on this website (including the text, graphics, videos and downloadable files) is owned by or licensed to Educom Pty Ltd and is subject to copyright and other intellectual property rights under international conventions

Syndesmotic Ankle Injury (High Ankle Sprain)

Syndesmotic ankle injury is also known as “high ankle sprain”. It is considered to be an under-diagnosed ankle injury, although still relatively rare when compared to the much more common plantar flexion–inversion sprain. The inferior tibiofibular joint is a syndesmotic joint (a joint in which the bones are united by fibrous connective tissue, including ligaments and membranes). Stability is provided by:

• The anterior tibiofibular ligament (or anterior inferior tibiofibular ligament)
• The posterior tibiofibular ligament (or posterior inferior tibiofibular ligament)
• The interosseous ligament, with further support provided by the interosseous membrane

Injury to the joint may be accompanied by diastasis (separation) of the tibia and fibula and fracture of the distal fibula. In these cases, the resulting instability of the talocrural (ankle) articulation leads to persistent dysfunction and vulnerability to further injury. Surgery may be required when instability is pronounced, and conservative management fails to deliver a satisfactory resolution. The mechanism of injury is not completely clear however, three scenarios involving excessive loading are provided:

• Dorsiflexion of the ankle
• External rotation of the foot
• Eversion of the foot and ankle

Many authors describe the most likely mechanism of injury as a trauma that combines forced dorsiflexion of the ankle and external rotation of the foot. Rupture of the anterior tibiofibular ligament is the first injury, followed by a tear of the interosseous membrane and, rarely, the posterior tibiofibular ligament. Except in relatively mild presentations, plain radiographs are advisable to help detect possible distal fibular fracture and diastasis of the inferior tibiofibular joint. Magnetic resonance imaging should also be considered.

Grading

Grade 1:

• Partial tearing of the anterior inferior tibiofibular ligament.
• No diastasis detected by imaging.
• Considered a stable injury.

Grade 2:

• Complete tear of the anterior inferior tibiofibular ligament.
• Partial tear of the interosseous membrane.
• No diastasis detected by imaging.
• Considered a latently unstable injury.

Grade 3:

• Complete tear of the anterior inferior tibiofibular ligament.
• Complete tear of the interosseous membrane.
• Partial or complete tear of the posterior inferior tibiofibular ligament.
• Diastasis detected by imaging.
• Considered an unstable injury.
• Typically occurs in conjunction with a fracture and a complete rupture of the deltoid ligament.

• A history of trauma to the ankle and foot involving ankle dorsiflexion, external rotation of the foot, eversion of the ankle and foot, or a combination of these.
• Localized pain over the anterolateral distal leg immediately above the ankle.
• Pain on weight-bearing and walking.
• Avoidance of heel strike when walking.
• Mild injuries do not prevent activities such as walking (although there will be some limitation to function).
• Severe injuries prevent further physical activities.

• Tenderness on palpation of the anterior aspect of the distal leg directly over the anterior tibiofibular ligament.
• Localized swelling (usually mild to moderate) directly over the anterior aspect of the inferior tibiofibular joint.
• Bruising (the extent of the bruising is dependent on the severity of the injury and damage to the associated structures. Bruising that is inferior to the medial malleolus is most likely and indicates an associated deltoid ligament injury).
• Pain on active and passive ranges of motion of the ankle and foot (most pronounced on passive dorsiflexion and eversion).
• A positive External Rotation Stress test.
• A positive Squeeze test.
• A positive Crossed-Leg test.

• Plain radiography may demonstrate the presence of diastasis (separation) of the syndesmosis and should help rule out concomitant fractures.
• MRI is considered highly sensitive for detecting injury to the inferior tibiofibular ligaments and for grading the severity of the injury.
• MRI is also highly sensitive for detecting concomitant injury to the medial and lateral ankle ligaments, as well as cartilage and bone damage.
• Diagnostic ultrasound is useful for examining the integrity of the anterior inferior tibiofibular ligament. When performed with dorsiflexion-external rotation stress, it helps to demonstrate a widening of the distal tibiofibular joint.

The following are examples of red flags for high ankle pain:

• Patient reporting severe pain
• Inability to bear weight
• Moderate to severe swelling
• Extensive bruising
• Deformity
• Severe tenderness on palpation or severe pain with any examination procedure

If any red flags are identified during history taking and clinical examination, referral for urgent medical evaluation and further investigation is warranted.

Conservative Management

For a faster patient recovery, we advocate a management approach that includes all of the following components:

• A gentle approach to correction of dysfunctional joints (if indicated)
• The inclusion of soft tissue therapy
• The provision of support and home advice
• The inclusion of rehabilitation exercises

Joint Dysfunction

In our experience, ankle sprains are often accompanied by joint dysfunction. We advocate management of this dysfunction by using an instrument-assisted procedure or by gentle manual manipulation and mobilization to avoid or minimize further strain to the region.

Ice or Heat?

The application of ice, particularly in the acute phase of an injury, is a safe and effective means of reducing pain whilst also reducing secondary hypoxic injury to the surrounding uninjured tissue by lowering tissue metabolism. This means that the damage is potentially confined to the injured area. Some practitioners advocate using moist heat in the subacute or chronic phase of an injury. However, we have found that patients often benefit from the continued application of ice to reduce discomfort and manage inflammation.

The application of ice helps to decrease the patient’s pain which then allows them to tolerate some movement. This helps the patient to maintain range of motion, stimulates circulatory perfusion, and prevents potential atrophy, all of which help to speed up recovery. Heat therapy may not be the best option for some musculoskeletal injuries as they often involve inflammation of the damaged tissues. Applying heat can potentially increase blood flow to the area and worsen the inflammation, leading to more pain and discomfort. Whilst heat therapy may provide temporary pain relief, by relaxing muscles and increasing blood flow, it does not address the underlying cause of the impingement. Therefore the use of heat therapy may delay recovery.

Differential Diagnosis of Syndesmotic Ankle Injury

The differential diagnosis includes:

• Distal fibular fracture (tenderness along the posterior margin of the distal 6 cm of the fibula)
• Tibial fracture (tenderness along the anterolateral tibia just proximal to the ankle joint line, adjacent to the anterior tibiofibular ligament)
• Talar fracture (deep ankle pain)
• Anterior talofibular ligament sprain (tenderness at the anterolateral ankle but more distal than with syndesmotic injury)
• Calcaneofibular ligament sprain (tenderness at the lateral ankle just distal to the lateral malleolus)
• Anterior ankle impingement