Presentation
Recurrent trauma, the patient fell off a horse and injured his left ankle
Patient Data
There is bimalleolar soft tissue swelling, lateral more than medial, suggestive of soft tissue and or ligamentous injury. There is a tibiotalar tilt. There is a left lateral malleolar cortical lucency of uncertain etiology and significance (possible avulsion injury). There is exuberant ossification of the distal tibiofibular syndesmosis (TFSO).
Case Discussion
The main cause of distal tibiofibular syndesmotic heterotopic ossification (TFSO) is usually due to previous trauma and syndesmotic sprain. When TFSO occurs post open reduction and internal fixation it is difficult to determine if the primary syndesmotic separation or the internal fixation resulted in the ossification. It has been theorized that syndesmotic ossification occurs post syndesmotic separation due to previous trauma, formation of a hematoma, and subsequent ossification of the hematoma with the resultant inferior tibiofibular osseous connection.
It usually arises approximately 3 cm's superior to the ankle joint and involves the inner cortex of the distal tibia and fibula. It may partially fuse and form synostosis or it may "kiss".If it involves a single inner cortex a surface osteogenic sarcoma needs to be excluded.
A positive trauma history usually assists in distinguishing TFSO from a rare surface osteogenic sarcoma at this site, alternatively if suspicious, then an MRI may need to be performed.
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