I'm just wondering what caused his legs to go like that?
Asking because I once put a lovebird's egg under a broody budgie (lovebirds were destroying their eggs for some reason) and the budgies hatched and brought up the lovebird's egg but the baby lovebird ended up with legs like that (I surmised because the budgies were not feeding it the right stuff - vitamin deficiency_). Anyway, I splinted the poor baby lovebird's legs just like the pup, and eventually its legs grew straight and it became normal, flew, and grew exceptionally bolshie.
That was years ago and wouldn't do it now.