How we use a 3D printer to replace ankle bones and restore movement
July 8, 2020
A human with metal bones? It sounds like something straight out of a comic book, but thanks to advancements in 3D printing, metal bones are very real.
For some patients with osteonecrosis (bone death) of the talus in the ankle, a 3D-printed implant can spare them from a lifetime of limited movement, and in some cases amputation.
The talus bone connects the foot to the ankle. It transfers weight from the leg to the foot and allows for mobility and range of motion. The talus has limited blood circulation, and a traumatic fracture or a disease such as sickle cell or leukemia can further reduce blood flow, causing the bone to die.
Until the last couple years, our only feasible options when this happened were amputation of the foot or surgery to fuse the heel to the leg. The latter leaves the patient unable to move the ankle and requires reconstruction to avoid a leg length difference, which significantly limits mobility.
Today at the UT Southwestern Department of Orthopaedic Surgery, we have another option: replacing the dead bone with a custom, 3D-printed metallic bone. There are only a handful of orthopedic teams in Texas performing this life-altering surgery, and so far the procedure has been covered by most patients' insurance plans.
Printing a 3D metal talus bone
The first step to creating a new 3D-printed bone is to take CT scans of the talus on your good foot. The image is reversed and used as a blueprint to create a new talus. We then work with a company to produce three trial implants made of plastic that are slightly different sizes.
Once we’ve determined the best fit, a final “bone” is printed ahead of surgery. The metal in the type I currently use is titanium. The dead talus is removed, and the new talus is set in its place.
The results are truly impressive. Replacing the talus with a 3D replica allows for movement of the ankle and subtalar joints, which makes moving the foot up and down and side to side possible.
I encourage my patients to return to an activity level with which they are comfortable. While a marathon may not be in the cards, I’ve seen my patients go back to active lives of working, chasing children, and participating in exercise classes.
What’s next in 3D printed bones?
The ankle is just the tip of the iceberg.
Using 3D printing technology to create bone implants is still an emerging field, but the possibilities to reshape the field of orthopedics are nearly endless.
Such implants open the door to the opportunity to correct genetic malformations or save limbs that have been damaged by trauma or disease. Procedures similar to what we are doing with talus bones are being tried for other parts of the body. For example, patients who lose a jawbone to cancer may soon be able take advantage of this technology.
Along with 3D printing solid bones, researchers are developing a 3D-printed “hyperelastic" bone. This synthetic bone implant resembles a scaffold or lattice and is designed to support the growth and regeneration of a new, real bone.
We look forward to the next breakthroughs in this advancing technology – and giving more patients hope using customized 3D printed bones.