I had a coon that ripped a chunk of thigh muscle the size of my fist out of one of my big hens in the middle of the night- it had entered the coop by squeezing through roof panels. I cleaned the wound as best I could and got some iodine and coated her wound with it, then sewed the major muscles as close to the anatomical positions as I could with cotton thread, then stitched as much skin back over the opening as possible with a crazyquilt of thread, and spread the bare area with Neosporin, and let her sleep the rest of the night and morning in a tupperware tub of horse bedding pellets until she got restless and wanted out.
She limped awful bad the first couple days - she had almost no rib or thigh muscles on one side, after all- but she improved rapidly despite looking like a Frankenchicken. In a couple weeks she stopped limping and her feathers started coming back in. A couple more weeks and there was no way to tell she had ever been Hurt without picking her up and feeling through the feathers for the stitches, which I never found but one end sticking out.
Wow! It is amazing she survived that! Fortunately, my hen’s wounds are not deep like that, just cover a large surface area.