Corrosion-free bearing technology for ankle joint prosthesis

In this prosthetic joint, the bearing must be resistant to impact loads and salt water

This joint for use in prostheses is a new development from Adaptive Sports Ankle Prosthetics. It contains plain bearings made of iglidur® J material and igubal® spherical plain bearings. The prosthetic joint was specially designed for use with high sudden forces, such as those that can occur in sport. Great importance was attached to maximising mobility, but also to special features such as resistance to seawater.

Profile

What was needed: iglidur® plain bearing, igubal® spherical plain bearing
Requirements: Bearings with a very low coefficient of friction were needed that can be used in or near salt water and are easy to install. They also needed to be manufactured in accordance with ISO 9001-certified QMS requirements and exceed the test conditions for dynamic and static load in accordance with ISO 10328.
Industry: Medical technology, prostheses
Success for the customer: Thanks to their material composition, the polymer bearings are extremely wear-resistant, resilient and self-lubricating. The bearings, which do not require external lubrication, are therefore also completely maintenance-free.

Prosthetic joint from Adaptive Sports Ankle Prosthetics

Problem

This new development is the only multi-axis ankle joint prosthesis in the world that has been specially developed for high impact resistance and can be used in water sports or for high impact loads, such as in equestrian sports. The joint drive force of the joint prosthesis component is provided by a spring torsion force, whereby the spring is enclosed in a titanium sleeve.

The bearings to be used in the prosthesis had to fulfil stringent requirements. The company was looking for bearings with a very low coefficient of friction. In addition, they must have low moisture absorption, be corrosion-free when used in or near salt water and enable the simplest possible assembly without the need for fastening elements. In addition, they must fulfil the QMS requirements in accordance with ISO 9001 and exceed the test conditions for dynamic and static load in accordance with ISO 10328.

In addition to the plain bearings, a ball and socket joint was required that can swivel radially during movement and can be offset by 20 degrees. This also had to be corrosion-free, maintain a low coefficient of friction, enable simple assembly and be CE-marked.

Solution

The designers of Adaptive Sports Ankle Prosthetics decided to use two bearings made of the all-round material iglidur® J and an igubal® spherical ball, which enable a high degree of flexibility in the prosthesis.

Our bearings are characterised by a number of special specifications that offer a number of advantages for this application. Thanks to their special composition, the polymer bearings are extremely wear-resistant, resilient and self-lubricating. As they do not require external lubricating greases, no dirt sticks to them, eliminating the associated wear and maintenance effort for cleaning and relubrication.

Equally central to the prosthesis is the use of the igubal® spherical plain bearing, a ball and socket joint that is also designed to swivel radially in the application. The polymer spherical plain bearings, which are more economical than metal bearings, are the perfect solution for the new prosthesis due to their lightness, simple assembly, dry running without lubricant and corrosion resistance, just like the iglidur® plain bearings.