This is an article I read about this. Just an article, I am not qualified to advise. Best of luck!!!
copied and pasted from
http://zebrafinchsociety.co.uk
"BROKEN LEG:
Fractured legs are not uncommon. In the majority of cases the negative treatment of leaving them alone is by far the best. If the break is high up, in the fleshy part (the so-called thigh) this method should be invariably adopted.
When the break occurs in the lower part you may attempt to set the break. In attempting to 'set' a leg a suitable sized quill makes an excellent splint. It should be cut to the proper length, slit open, and trimmed to make it fold nicely round the shin. Place the edges of the bone neatly together, pad the leg with a little cotton wool, put on the quill splint and bind it firmly but not too tightly with thread. Leave the splint undisturbed for three or four weeks, so that a firm union be made before attempting to remove it. In all cases keep the bird in a moderate-sized cage, in a quiet place; place perches low down and keep food and water within easy reach of the bird. It is imperative to act promptly.
BROKEN WING:
It is not advisable for the beginner to 'set' a fractured wing. It is sometimes believed possible to assist matters by binding an injured wing in a natural position against the body, but this does not by any means ensure that the fractured ends of bone are being brought together in the proper position, and the risk of the bird pulling the bandage out of position is very great.
The only rational treatment for a broken wing is to leave it alone, and place the bird in a moderate-sized cage, with low perches arranged in a most convenient position, and place food and water where the bird can get at them with the least possible effort. Then keep the bird in a very quite place, and place a light cover over the front of the cage for the first fortnight. The object is to keep the bird as quiet and still as possible until nature has repaired the damage in her own way.
If you find yourself with any form of health problem in your stock that you dont understand, you should contact an experienced fancier or alternatively a veterinary surgeon.."