i've had my share of leg problems. Peaceful is right, you do seem to have more leg problems when the chicks are hatched in an incubator. From what you are describing, it sounds fairly extreme, either a knee or hip misalignment. i would recommend euthanasia. i've tried nursing chicks with bad legs. Seems if they are going to correct they do so quickly, like fixing spraddle leg with the bandaid. i just went through a month of leg braces with a little australorp. After numerous vet visits, different braces, (lots of money), we came to the conclusion that the leg was not going to correct, and in fact the other leg was going out, too. She couldn't walk at all, and cried all the time. Made the hard decision to put her down. It was made more difficult by the fact that i had her for over a month, and she was the sweetest thing, but it just wasn't going to be a good life for her.
Anyhow, that's just one situation i've had with leg issues. i had another last year that went badly, also. Tried to keep her alive for about four months. So, i guess from my experience, if i were to come across another serious leg issue again, i would opt for putting the chick down before it has to suffer too much.
i wish you the best in whatever you decide. i know it's not an easy decision.