Which splint extends from the ankle to the armpit for support?

The correct answer is the long board splint, which is designed to provide extensive support for the entire length of a limb, extending from the ankle to the armpit. This type of splint is commonly used in situations where a stable and rigid support is necessary to immobilize fractures or severe injuries along the limb. By offering continuous support from the lower extremity through to the upper body, it helps to prevent movement that could exacerbate the injury.

In contrast, a coaptation splint is typically used to stabilize fractures in the upper arm and would not cover the full length from the ankle to the armpit. A traction splint is specifically designed for use on femur fractures and focuses on applying traction to align the broken bone, rather than providing comprehensive support. A functional splint is employed to allow for movement during recovery, which is not the goal when immobilizing a serious injury as required with the long board splint.