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Case Discussion #21: bilateral syndesmosis injuries

Mr S is a 34 year old gentleman who sustained an acute dorsiflexion injury to his right ankle whilst riding a motorbike. He initially felt a 'pop' in his ankle and immediate pain anteriorly. He struggled to weight bear after the incident and his astute Physiotherapist was concerned about the potential for a syndesmosis injury, and referred Mr S to his General Practitioner for further investigations and review.


Initial x-rays were normal (as is common with syndesmosis injuries) and in particular there was no evidence of posterior malleolus fracture which is pathognomonic for syndesmosis injury. As Mr S still had ongoing pain when weight bearing, significant swelling and bruising, he was referred to Dr Touzell for an opinion. An MRI scan confirmed a complete rupture to the anterior inferior tibio-fibula ligament as well as the interosseous membrane, consistent with a significant syndesmosis injury (see below).

Syndesmosis injuries have a high rate of ongoing pain and instability so operative intervention to stabilise the syndesmosis was discussed with Mr S. It was also nearly eight weeks following his injury, and Mr S felt his symptoms were deteriorating rather than improving. Due to high activity levels and relatively young age, the decision was made to proceed with surgical stabilisation. An ankle arthroscopy to obtain direct inspection of the distal tibio-fibula joint to assess for stability was performed, then subsequent stabilisation with two flexible suture buttons was performed (see below).

Mr S was non weight bearing for two weeks, then commenced partial weight bearing in a CAM boot for a further four weeks. He was referred back to his treating Physiotherapist for strengthening and rehabilitation, and was weight bearing comfortably and able to return to impact activity three months following surgery.


Mr S was so comfortable returning to high impact activity, he had exactly the same injury to his left ankle whilst riding a motorbike six months later! A repeat MRI scan demonstrated the same pattern of injury, this time to his left ankle, with rupture to the AITFL and interosseous membrane. He presented straight to Dr Touzell and syndesmosis stabilisation was again performed.

Mr S underwent the same rehabilitation program and recovery for his right ankle. He returned to sport three months after his second surgery. Two years following his initial injury, Mr S has minimal ankle pain and no instability. He has occasional stiffness, particularly after playing sport, but has returned to all regular activity including motorbike riding.



DISCUSSION

The syndesmosis is made of three components: the anterior inferior tibio-fibula ligament, interosseous membrane and posterior inferior tibio-fibula ligament. Syndesmosis injuries can occur after forced dorsiflexion/external rotation injuries, such as landing from height, getting caught at the bottom of a tackle or landing on a motorcyle pedal. They are often a delayed presentation to the orthopaedic surgeon as initial x-rays are normal or the injury is misdiagnosed as a simple ankle sprain. A simple injury to one component of the syndesmosis (usually the anterior inferior tibio-fibula ligament) can be treated non-operatively. Non operative management involves careful protection of repeat dorsiflexion with a CAM boot for six weeks, then progression to high impact activity three months after injury. However, injury to two or more components of the syndesmosis often results in chronic pain and instability, requiring surgical stabilisation in a young, active patient. Syndesmosis injuries can also occur in conjunction with injuries to the lateral ligament complex, the anterior talofibula ligament, calcaneofibula ligament and posterior talofibula ligament. This is often a cause of chronic instability and pain following a seemingly innocuous ankle sprain, or patients can injure their syndesmosis in the setting of chronic ankle sprains and subsequent ligamentous injury. An MRI scan is the investigation of choice, however in the setting of an equivocal diagnosis or chronic syndesmosis injury, a weight bearing CT may help demonstrate functional syndesmosis instability and help determine if stabilisation is required.


All cases and clinical photographs have been shared following discussion and written permission from the patient and/or guardian.

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