Hi Son,
I think you have nailed it really,
I agree there is a haematoma straddling the interosseous membrane.
In the short axis I am convinced there is a tear of the interosseous membrane with a haematoma either side of it.
In the long axis it is more difficult to appreciate the defect, however the haematoma is obvious.
I think the only thing that makes sense here is that the trauma has perforated the interosseous membrane and then it has bled causing the haematoma.
It is a lovely case and it is a diagnosis that I very rarely make.
Your case is the second one I have seen this year where I have been convinced of an interosseous membrane defect.
You can tear the interosseous membrane as an extension of a high ankle sprain AITFS injury and in your case it seems it is just a direct impact injury.
Whenever you tear the interosseous membrane it is really painful and the patient is unlikely to be able to weight bare.
The reason there is no bruising is that the blood is trapped adjacent to the interosseous membrane by the overlying muscles (tib ant and tib post) so has no access to the subcutaneous space. Hence there will be some clinical swelling and tightness of the anterior compartment but no swelling.
It reinforces the idea that it is indeed worth looking at the interosseous membrane in patients with high ankle sprain symptoms or direct calf trauma.
I love your work,
This is worthy of being case of the week,
Let me know if you would like me to record it as case of the week.
Cheers
Steve.