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VR Interfaces: STAR Ankle


Overview of STAR Ankle
The STAR ankle - Scandinavian Total Ankle Replacement - is the product of Small Bone Innovations Inc. It is a prosthetic replacement ankle joint, that has been designed to precisely mimic the bones of the original, natural ankle, preserving the full original range of movement.

Consisting of three pieces, one piece anchors to the tibia in the leg, another piece anchors to the talus bone in the foot, whilst the third piece moves freely between them, held in place by plasmatic compound that serves as cartilage.

The tibial section is predominantly titanium, and is polished to a high mirror shine on the joint side, minimising any potential sticking points. Everywhere else, it if gnarly and rugged, designed to encourage bone growth on the surface as much as possible, as the piece is integrated into the end of the damaged tibia. Two screw columns help facilitate this, drilling deep into the healthy bone to anchor it.

The talar section is likewise predominantly titanium, and is polished to a high mirror shine on the joint side. Also likewise, everywhere else is rugged to encourage bone growth, and the joint is anchored via two screw pins, deep into the talus at the back of the foot.

The middle piece, is essentially a bearing ball joint, and slides back and forth between the two sections. It is made of a solid chunk of ultra high molecular weight polyethylene between 5 and 10mm in height.

No actual nerves are tied into the STAR, which has been implanted in over 19,000 people at time of writing. However, the implant basically replaces the damaged bone ends, with muscles reattached around it, as the bone grows, so this is not the problem it seems like. The implant is solely there to avoid pinning the bones, and allow a person to retain full use of the foot after an ankle seizes up as is the case with severe arthritis, or foot damage.

Likewise, the joint itself is a definite interest piece for the design of a fully prosthetic foot, as it basically replicates the movement range of a natural ankle exactly, without compromising on the load bearing abilities of the foot.

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