Presentation
Pain in the anterior compartment of the left leg.
Patient Data
Plain radiography showed a bony bridge between the middle thirds of the tibia and fibula. Also noted on lateral view a subtle linear sclerosis across the tibial diaphysis right at the level of the synostosis
A bony bridge is noted connecting the mid third of the tibial and fibular diaphyses along the expected location of the interosseous membrane. Also there is T1 hypointense line traversing the cortex right at that bony bridge without any surrounding edematous change.
A small subcutaneous edema is identified along the medial aspect of the tibia.
No periostitis or soft tissue component is seen.
The imaged muscular compartments are unremarkable.
Case Discussion
Synostosis of the middle-third of the diaphysis of the tibia and fibula is rare. Similar conditions have been noted in runners and basketball players, all of whom presented with anterior shin pain for one or two years. Due to the chronicity of the symptoms in these cases the synostosis was
attributed to an occult stress fracture or severe ligament sprain. In our patient there is linear sclerosis across the tibial diaphysis right at the level of the synostosis .This finding might be curious post-traumatic change from an old stress fracture .
Also, the location of the synostosis suggested that the etiology was that of a stress phenomenon to the interosseous membrane.
Depending on the location, synostoses may be asymptomatic,resulting from an accompanying deformity of the limb segment. Symptomatic synostoses of the lower limbs are a cause of pain and have been thought to be associated with stress fractures of the fibula.
Several causes of synostosis have been described. Congenital types may be associated with multiple hereditary exostosis and typically present at an earlier age. Other causes include trauma, predominantly to the distal tibia and fibula and ankle. In these cases the synostosis is believed to result from a hematoma tracking between the two bones, and undergoing calcification on the interosseous membrane.
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