Researchers Explore Robotic Prosthetics That Connect Directly to Bone and Soft Tissue

Breakthroughs in robotics have birthed a new generation of prosthetics that increase mobility and control. Future technologies could usher in cybernetics that are far more deeply integrated into the human body than anything currently available.

New research out of MIT highlights technology that bucks the traditional prosthetic socket model for a system that plugs more directly into the human body. A recently published paper titled, “Tissue-integrated bionic knee restores versatile legged movement after amputation” highlights a method wherein the hardware plugs directly into human bone and tissue.

The team hosted a small clinical study involving subjects with transfemoral (above-the-knee) amputations. The early results are promising.

"A prosthesis that's tissue-integrated — anchored to the bone and directly controlled by the nervous system — is not merely a lifeless, separate device, but rather a system that is carefully integrated into human physiology, offering a greater level of prosthetic embodiment. It’s not simply a tool that the human employs, but rather an integral part of self,” according to the study’s lead author, Hugh Herr.

A titanium rod is inserted into the femur at the point of amputation in a method known as osseointegration. This helps leverage the skeleton as a support structure, rather than the contact point between the residual limb and the prosthesis. That older method can cause discomfort and skin infection.

The surgeons were able to reconnect pairs of muscles within the existing limb, allowing for increased communication. This provides the wearer sensory feedback, while generating an electrical signal that can control the prosthesis more naturally. Electrodes collect information from AMI muscles, transmitting it back to the prosthetic through a series of 16 wires.

“Another reason this paper is significant is that it looks into these embodiment questions and it shows large improvements in that sensation of embodiment,” Herr adds. “No matter how sophisticated you make the AI systems of a robotic prosthesis, it’s still going to feel like a tool to the user, like an external device. But with this tissue-integrated approach, when you ask the human user what is their body, the more it’s integrated, the more they’re going to say the prosthesis is actually part of self.”

Herr expects the FDA approval process should take around five years.