How does a cast help with the healing process of a broken thumb?

Doctors use spica casts for both surgical and nonsurgical treatments of broken thumbs to hold the bone fragments in place during the healing process, notes OrthoInfo. Broken thumbs heal well if the bones remain in a stable position.

People who do not have surgery for broken thumbs generally wear spica casts for four to six weeks to hold fractured bones in place, states OrthoInfo. Patients must have regular X-rays during this time to ensure that the bones have not moved. If doctors perform surgery for broken thumbs, patients wear casts or splints for two to six weeks to stabilize the bones.