When my filly sliced her leg open and lacerated the extensor tendon [much similar injury to Walter's, but not as bad] we had proud flesh that bad.
Proud-Aid [idk if you can get it in the US] did wonders, never had to have the vet out to cut off anything. Four months down the track and she has a scar, and a big lump on her leg, but is sound as a bell and healing wonderfully. I've been riding her on and off since just shy of 3 months post-injury and would in fact have been able to get on earlier, but wanted to play it safe. The vet said 3 months rest so the tendon could heal.
I can't remember what it cost but it wasn't crazy expensive and I still have 3/4 of the pot left so I have plenty for the next injury. I have horses... injuries are inevitable lol.