I found this thread last night in a frantic search for some sort of care for my hen. Came home to find her larynx and attached anatomy hanging out through a hole in her neck, as if she got caught on something.
As a vet tech for 15+ yrs, this was probably the most horrific thing I have seen, but thankfully I had some sort of supplies on hand (even if make-shift) for repair, as there is no one local I have found who offers avian care, to include chickens. I was able to get her put back together, so to say, and she made it through the night. I applied the lavender oil to her injury/suture site as suggested and immediately she began acting better. She has eaten and drank a little this morning, and even "talked" to us and my cat when he came to check on her. Still no idea as to what happened, the other three hens are just fine. Not out of the dark yet, but all the info that has been posted here has given me a bit of relief knowing that there are other options besides "wait and see".