Orthopaedic surgeons in Baltimore have pioneered a new approach to treating avascular necrosis of the talus, using 3D printing technology to create a replacement bone, tailored to the patient´s specific dimensions.
The talus is a large bone in the ankle that allows the foot to move in different directions. In a high impact injury or traffic accident it can become fractured, and this sometimes results in avascular necrosis — the death of the bone due to a lack of blood supply.
“The talus has limited blood circulation, and when it is fractured, that blood circulation is commonly lost. The result is avascular necrosis,” explained Dr. Mark Myerson, director of the Institute for Foot and Ankle Reconstruction at Mercy Medical Center. “Over time the bone will crumble and collapse, like a squashed orange. You´re left with a flattened, painful and arthritic ankle. When you remove the dead bone from the ankle you are left with a massive hole. The treatment offered to patients to date has been to fuse the heel to the leg (the tibia) and these results are particularly poor. The patient is left with a stiff ankle without any movement at all. However, we have a new method of treatment which is truly unique.”
At the hospital in Baltimore, surgeons have been imaging the patient´s healthy ankle with a CAT scan, and then using computer engineering to reverse the image making it a blueprint for creating the new talus.
Several trial implants, made of plastic, are produced to determine the best fit. The final prosthesis to be inserted is made of cobalt and chrome.
“This is not an ankle replacement,” Dr. Myerson said. “An ankle replacement may be appropriate for a patient with ankle arthritis, but it cannot be done with patients with avascular necrosis of the talus.”
Patients who receive the 3D-printed talus replacement may regain up to 75% of normal ankle function, Mercy Medical Center reported.
“If you have a fusion, there is no movement. The talus replacement allows for the movement of both the ankle and subtalar joints which make moving the foot up and down and side to side possible,” Dr. Myerson explained.