[Short-term follow-up of a series of 21 uncemented total ankle prostheses]

Revision rates after total ankle arthroplasty in sample-based clinical studies and national registries

BACKGROUND

The aim of this study was to evaluate the outcome of specific implants in total ankle arthroplasty as reported in clinical studies and determined by national registries.

MATERIALS AND METHODS

A structured literature review was conducted regarding sample-based clinical studies and national registry data. To allow for comparative analyses, registry data had to be available for the implants included. These were STAR Ankle, Büchel-Pappas, Hintegra, Mobility, Agility, and Ramses Total Ankle Arthroplasty. The revision rate was used as the main outcome parameter.

RESULTS

On average, the revision rates published in sample-based clinical studies were about half the value found in registries. Implant developers represent a share of almost 50% of the published content and are therefore over-represented in scientific publications. The inventors of STAR Ankle and BP total ankle implants published data which was statistically significantly superior to the outcome achieved in average patients as documented in registries. Irrespective of the implant, the average revision rate to be expected according to the registry data available is 21.8% after 5 years, and 43.5% after 10 years.

CONCLUSION

The average revision rate published in peer-reviewed scientific articles was significantly lower than the outcome achieved according to national arthroplasty registry data, which reflect actual average patient care in the respective countries. Publications by some research groups, particularly by implant inventors, show a deviation from the outcome published by other users and those shown in registry data.

Total ankle replacement

Total ankle replacement is emerging as a viable treatment for symptomatic ankle arthritis that has not responded to nonoperative treatment. Most modern implant designs involve the use of a three-component, mobile-bearing implant. Although the results of the different design approaches are encouraging in limited clinical series, there is still the need for careful, long-term analyses to estimate to what extent the current designs are mimicking the biomechanics of the ankle joint. More attention must be paid to more accurate implantation techniques that result in a well-balanced ligament and allow the ligaments to act together with the replaced surfaces in a most physiologic manner. To improve the stability of the bone-implant interface over time, specific efforts should be made to better understand the extrinsic and intrinsic forces of the ankle joint, including the forces that are created by the prosthesis itself.