Thrombosis in thalassemia major /intermedia

I am on off transfusion and on hydroxyurea , folvite and b12 .HB 9 to 10 GM's in last four years got 2 times Deep vein thrombosis and 3 times superficial Thrombosis in legs .
What's major reason
Spleentomy has been done was in ecosprin 75 and blood thinner after blforst time of thrombosis
Still getting repeated thrombosis .
Pls advice

It's a known issue once the spleen is removed. Other than taking aspirin or vitamin E, I don't know if there are any effective treatments.