Hi Son,
Great images and clip,
In my opinion the primary pathology in this case is a compressive tendinosis of peroneus brevis that has developed into a longitudinal split.
We had a great protection at the Melbourne anatomy day past weekend where the old cadaver had exactly the same pathology and we could see how the peroneus brevis had become thin and wrapped around peroneus longus at the level of the lateral malleolus and then had developed a longitudinal split that I could put my examination stick through.
Your case is exactly this pathology.
I also agree that there is a large peroneal tubercle.
BUT
In my view the large peroneal tubercle is not the primary problem here (it may be a secondary point of irritation for peroneus brevis) but the primary pathology is the compression of brevis by longus proximal to the tubercle and the longitudinal split.
I would not refer to this as a peroneal tubercle syndrome stenosing tenosynovitis.
When it is true peroneal tubercle syndrome stenosing synovitis (in my view) it most commonly affects the peroneus longus and the peroneus brevis is relatively spared. There would be a thick inferior peroneal retinaculum at the level of the tubercle (which is absent in this case.
So in my view this is a compression tendinosis and split tear of brevis and an incidental large peroneal tubercle.
Great case.
Steve