Biomedical engineers at Columbia University Medical Center have implanted a joint-shaped scaffold infused with a growth factor protein that allowed rabbits to begin using their injured forelimbs again in one month.

At two months, the animals moved almost as well as similarly aged healthy rabbits. The study is the first to show that an entire joint can be repaired while being used.

In the study, the researchers first imaged the damaged forelimb joint and then created a three-dimensional picture of it. They used a bioprinter to “print out” a precisely accurate, three-dimensional copy of the joint, but criss-crossed it with tiny interconnecting microchannels to serve as a scaffold for new bone and cartilage growth.

The approach has several advantages. It’s impossible to re-create in a dish the array of signaling chemicals the body uses to generate the diverse cell types in different tissue, and it’s much easier to get approval from regulatory agencies to implant a scaffold than whole tissue.