Final answer:
When your arm is broken, so you will need a cast to immobilize a broken arm to promote proper healing by preventing movement at the fracture site, aligning the bone fragments correctly, protecting the arm, and reducing pain.
Step-by-step explanation:
When you have a broken arm, it is important to immobilize the bone to promote proper healing. A cast is a rigid support made from plaster or fiberglass that holds the broken bone in place while it heals. It prevents movement at the fracture site and provides support to help align the bone fragments correctly. The cast also helps protect the arm from further injury and reduces pain.
For example, if your ulna bone is broken, a cast would be applied to keep it stable. The cast may be applied from your hand to just below your elbow, or it may cover your entire arm depending on the location and extent of the fracture. The cast is typically worn for several weeks until the bone has healed enough to support normal activities. So therefore a cast is needed to immobilize a broken arm to promote proper healing by preventing movement at the fracture site, aligning the bone fragments correctly, protecting the arm, and reducing pain.