Often keeping the wound clean will allow healing to take place. However, as you have noticed, secondary lameness issues will have to be dealt with. Massive trauma usually results in tendon damage that will leave the leg permanently defective. Not to worry though as chickens can learn to walk peg-legged and you only have to worry about the injured bird maintaining her status within the flock. Watch her and make sure she is not being picked on by the others once she is returned to the flock.
The drugs I like to use for severe trauma is torbutrol, valium and if needed baytril for infection. The first two drugs are controlled substances and are available from a veterinarian. They work well for pain and easing stress in certain avian patients. However, many flock owners can't afford all this, and simply supplying basic care will work wonders. Cleaning the wound, keeping it bandaged, and giving the patient a quiet place to recover is never the wrong thing to do.
Hope this helps. And good luck!
