Once the infection gets to the legbone, no amount of antibiotics will stop it. The staph infection quickly spreads throughout the body.
You can try Baytril. Here's a link where you can buy it. I recommend that you expedite shipping when ordering it.
https://allbirdproducts.com/collections/bird-medications/products/baytril-10
Dosage is given orally using a syringe without a needle, 0.05ml per pound of weight 2 times a day for 5 days.
Baytril is top of the line and if Baytril doesnt work, nothing will.