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Total Ankle Replacement

The Bison TAR

Bison TAR CAD Model

The Department of Mechanical Engineering has developed an improved design that addresses the major limitations of current TAR approaches.


Total Ankle Replacement (TAR), also known as Total Ankle Arthroplasty, is a orthopaedic surgical procedure used to treat end-stage ankle arthritis. Ankle arthritis, a form of osteoarthritis, is caused by the breakdown of cartilage in the joint which leads to inflammation and pain. 

Ankle Joint


Before TAR's were significantly implemented into ankle arthritis treatment, arthrodesis, or ankle fusion, was the primary technique for reducing the pain in patients; however, fusing the ankle bones together greatly reduces the joint’s range of motion, and could potentially cause serious alterations in gait, which can cause additional pain and joint damage in knees, hips, spine, and muscles

Ankle Joint Movement
Ankle Fusion


Total Ankle Replacement (TAR) is a surgical method to treat ankle arthritis using a prosthesis to mimic the function of the ankle.

Current ankle prostheses have a 75-80% survival rate ten years after initial surgery which causes many patients to outlive their TAR and requires repeated surgery over time.

TAR failures are due to large magnitudes of stresses caused by large forces applied over small contact areas of the prosthesis components during the life of the TAR. These stresses cause increased wear rates of the bearing component. Maximum stresses and the number of cycles the bearing component is subjected to are the main factors determining the lifespan of the TAR.

A new design developed by North Dakota State University provides solutions for the previously stated issues facing current TAR’s. The NDSU design is inverted compared to the typical three component design and incorporates the use of advanced composite material. Preliminary finite element analysis suggests the NDSU design provides more benefits than current in market TAR’s.

Current Research

Wear testing was done on component material combinations implemented in current TAR’s with the incorporation of the proposed advanced composite material. Preliminary results suggest that the composite material exhibits better wear rates in TAR’s versus traditional TAR material combinations though more testing is needed and is ongoing.

Testing and research is currently ongoing to obtain more results. The NDSU TAR addresses issues facing current in market TAR’s and suggests the NDSU TAR will provide a better quality of life for patients requiring ankle arthroplasty. 

Student Focused. Land Grant. Research University.

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Last Updated: Monday, October 24, 2016 2:12:29 PM
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