I've had this happen . A roo had a leg injury and the vet put it down that now I'm sure I could of saved. I also had an older duckling that got mangled by a dog. Lacerations, torn ligaments and broken leg in more than one place. (we have a lovely neighbor that lets her pitbulls loose that have no problem tearing up coops and going over a chain link fences) A friend of mine showed me how to wrap with vet wrap around the body setting the leg underneath lined with cotton. I had to also soak the leg with disinfectant daily. The duck stayed in a tight box with paper towel wadding to help support him and I basically hand fed it for a few days. The duck just kept getting better and limped for months but now it moves without a hint of injury. Maybe 6 months total for complete recovery After the box treatment he then got to keep baby goslings company in a small coop where food and drink was effortless. If you wait too long to set the leg, the bones start to calcify in the wrong position requiring a rebreak. I think tight confinement and hand feeding is the hard part but necessary for success. The duck was very cooperative and quickly figured out how to drink out of a small bowl I held for him. In your chick's case I don't think he'd be as cooperative as a duck. Laying low and staying still seemed to be instinctive for the duck. Chicks struggle more, but I'd still rig up a box, with a cardboard panel for his legs to hang through where they should hang but touch the floor of the box combined with vet wrap. Basically set him up as his leg should be but no way to redamage his leg for a few days. I'm not a fan of pine shavings, especially loose and deep. I'd use pelleted pine bedding with a layer of paper towel over it for a few days afterward. Traction and support are better than struggling in deep fluff.