I ran across this article a couple of months ago, but what stuck with me was this image:
photo credit: A’ Design Awards. Ultrasound could be the killer app that makes 3D printed casts take off
The holes in a cast allow for better “breathing” room for skin while you have to endure the 6+ weeks a typical broken bone takes to heal. This is a latticed cast that is printed in two halves for a custom fit, based upon scans and x-rays. The holes near the injury site are made smaller, but big enough to accomodate the leads as shown, which provide electrical stimulation to expedite healing bone growth. The one pictured actually has a portable ultrasound generator. Since these probes need to make contact with the skin to provide effective treatment, this is a better cast to facilitate that since cutting holes in plaster and fiberglass often leads to cracked and ruined casts. Seems like it would cut down on the itchiness that inevitably occurs during those long uncomfortable weeks of healing.
The full article can be found here: http://www.iflscience.com/health-and-medicine/3d-printed-cast-speeds-bone-recovery-using-ultrasound