Had a similar event about 2 months ago. Actually had to do some sutures , as my hens entire tail end was drooping and back was flapped open . Not an expert by any means. Cleaned wound thoroughly with saline irrigation and peroxide. Applied Microcyn antimicriobial spray several times a day, kept her segregated ( in the house in a dog kennel) for about 3 days. First day very quiet not eating drinking much...pretty well in shock, but about half way through second day doing better, gave some lytes in her water and extra protein in her feed. I think i repeated irrigation and peroxide day 2. (Just to make sure clean). Kept her clean and used the antimicrobrial spray several times per day. She was raring to go by day 4 and I let her out in gen. pop. ( I sprayed all open areas with Blukote, so the other girls wouldnt peck at her). I tried one of those hen capes, but the one i had was too big on her. After a few days, she was starting to scab over along incision line (could have used a few more sutures), so I'd rinse off entire back with warm water and check for infection/flies etc. Almost daily for about a week and then cut back after that. She really did great. Feathers are now filling in. Wish I would have got a pic when she was flapped open before my nurse skills took over. She was a trooper, didn't miss a beat laying when I had her segregated. I took the opportunity to give the flock a little extra protein and added some electrolytes to the water. Good luck! Chickens are super resilient! Still not sure what got mine, it was as if something tried to lift her up by the tail feathers or back.... we live in rural north Texas, so there is no telling.
