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One of the great challenges in biotechnology is interfacing synthetic materials with biological ones. Our bodies are designed with an extremely complex network of tissue, vascular, and neural structures to protect us and alarm us if there is something potentially dangerous to our system. If we sit for too long, for example, we feel discomfort and shift positions instinctively. If something is pressing against our leg and threatens to disrupt normal blood circulation, we perceive this threat with pain and pressure and respond accordingly.

Amputees and prosthetists have long been facing the issue of how to interface the residual limb with a prosthetic socket. Fitting for a prosthesis introduces a synthetic limb component to a biological one, and an improperly fitted socket can cause pain, pressure sores, and expose a residual limb to infection and tissue damage. And while there has been much improvement from the crude iron prosthetics that amputees once had to endure, there is still much room to improve to make the interface closer to a natural one.

One group at MIT has sought to address this disparity by developing a variable impedance prosthetic (VIPr) socket. Using MRI imaging and surface scanning techniques, researchers were able to find the tissue depth and where the socket was most likely to place pressure on the irregular bony areas of the residual limb. A socket was then 3D printed using this data to apply the least amount of pressure when fitted to the amputee.

After testing this socket on a below knee amputee, it was found that there was a 7-21% decrease in pressure on various bony areas of the leg compared to a regular socket during walking. While there is still no perfect socket or prosthetic interface for amputees, this is a step in the right direction to protect valuable and vulnerable human tissue.

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