While many splints can be improvised from expedition gear, carrying a few things can just make life simpler.  For example:

• A padded aluminum splint is small, lightweight, and can be used for splinting forearms, wrists, knees, ankles, and individual digits when combined with a T-shirt roll or a self-adhering bandage.
• Three or four blanket pins makes improvising a buddy splint much easier and faster.