Spraddle leg can happen for a variety of reasons from slippery surfaces, too much room in the incubator upon hatching, or just a simple slip and fall. Baby chicks are delicate but the majority are also hardy and will bounce back with a little help.
When you notice a chick has splayed legs the best thing to do is get it braced as soon as possible. The younger they are and the sooner it's caught, the better their chances will be.
I like to use a plain and simple band aid. It can be done as a one man job but I like to use a helper. Have your helper hold the chick on it's back so legs are facing you. Bend the legs to where they would normally go and simply wrap one end of the band aid around the bottom portion of each leg so that the bulk is on the middle.
Now the fun begins. At first the chick won't be happy and may need assistance for a bit however once it gets the hang of it's handy braces it will be cruising with the rest of them. I like to recheck the braces after a week. If all is good then the braces come off however if their is still splaying, rebandage and check again in another week.
There's some great videos online to help show progress and how to brace.
I am a 2nd grade teacher by day and a full time farm wife by evening (and weekends and the summer!).