Thanks for the ping!
I often wonder if someone couldn't create prosthetics for chickens and small critters using 3D printers (of which I have zero understanding). Wondering if there is a type of splint or brace which could be created with rigid foam, tiny dowels, vet wrap or whatever that can be used during the day and removed at night.
The short answer is yes, it's definitely possible to 3D print splints and prosthetics. Here are two examples, a prosthetic and a brace used on chickens specifically:
"Creamy the hen and her 3D printed foot":
https://libnews.umn.edu/2018/07/creamy-the-hen-and-her-3d-printed-foot/
A chicken leg brace design someone on reddit used (there are pictures of it on the chicken in use):
The fine print of the process is that those kinds of models often have to be designed on a case-by-case basis, and rubbing/sores over time is a huge risk for long term usage. So usually it's better to avoid braces/prosthetcis if there's any other option to help the bird compensate or recover. For short term usage like correcting curled toes in newly hatched chicks over a few days that risk is negligible but the design process becomes much trickier for adults.
For injuries that can potentially heal (vs amputation, etc.), it's also questionable whether to even employ any kind of prosthetic or cast. Too much assistance or comopensation can prolong the recovery in some cases for soft tissue damage where range of motion and muscle strength can become a "use it or lose it" situation.
In this case, it sounds like the hen is able to hold her foot up or pull it in rather than letting it flop - which is very important, that means some things are still working and this sounds like it isn't a paralysis or missing limb segment situation, so I would actually advise against designing a support brace or similar kind of thing. I once dealt with a bad soft tissue leg injury in a hen that took months to heal (badly torn muscle and damage to ligaments around the knee). I initially kept her in a kennel-style rabbit cage with a liner filled with shavings and hung small food and water containers on the side so she didn't have to move much to get access. Once she had some ability to amble about and needed to move back out with her flock, she got a 12"x15" platform at roost height (~20") that was accessible by a ramp with a strip of rubber mat on it for grip. I only let her have access to that once it was clear she could survive a crash landing if she made a poor choice. As already mentioned, the recovery process took MONTHS for the joint to firm up and muscles to get their strength back. Ultimately she healed very well but still get limpy in cold weather and still makes use of the ramp and platform. If you want to put the hen to roost with other adult chickens but are worried about her getting picked on or trying to get onto the roost and injuring herself more, if your coop design permits you can put a small pet carrier inside the coop and place her in there before everyone goes to roost, then take her out later.
