High 5-year revision, complication rates seen with three-part total ankle design

Investigators note that the implants which remain in situ result in generally good quality of life outcomes.

Issue: December 2009

VANCOUVER, British Columbia — A study investigating the New Zealand experience using a three-part mobile-bearing total ankle design shows a 27% revision rate at 5 years.

“We have a high revision rate at 5 years and a high perioperative complication rate,” Dawson C. Muir, MD, MBChB, FRACS, said during his presentation at the 25th Annual Summer Meeting of the American Orthopaedic Foot and Ankle Society. “Our patients with the ankle still in situ generally report good ankle-specific quality of life outcomes.”

Session moderator, Michael J. Coughlin, MD, said that other surgeons may have different revision rates.

“Those comments should not reflect on all of our experiences with total ankle arthroplasty,” Coughlin said. He noted that the study included a few patients with X-rays that indicated severe osteopenia.

STAR

Dawson and his colleagues retrospectively reviewed 52 Scandinavian Total Ankle Replacements (STAR, Small Bones Innovations Inc.) that were implanted in 49 patients in New Zealand between 1998 and 2005. Eleven surgeons performed between one and 13 operations.

Five patients died during the course of the study and five patients refused to participate; leaving 41 STARs available for review. The remaining patients had an average age of 65 years at the time of the surgery and a mean follow-up of 5 years.

The investigators discovered the patients had a mean Oxford ankle score of 25.6 and a WOMAC score of 18.9. The patients had a mean SF-12 physical health score of 42 and an SF-12 mental health score of 54.

X-rays

Overall, there were 11 revisions during the follow-up including six ankle fusions, three major revision procedures and two bearing exchanges.

Of the 30 X-rays available for review, the investigators discovered that six patients sustained intraoperative malleolar fractures, five patients had undersized tibial components and three patients had oversized talar components. Follow-up X-rays revealed evidence of mild tibial or talar component subsidence in five patients.

Muir said that the problem with the STAR and all total ankle replacements is the unpredictable outcome which can stem from inaccurate bone cuts and inferior matching of implants to bone.

“It is an unforgiving operation,” Muir said. “Surgeon experience is clearly important and this has been drawn out in this study.”

Coughlin said that the study highlighted the importance of patients election. “[Once patients] finally meet your criteria to do this, I think that you will have a high rate of success. But, I think that there is a lot of heartache in doing this and it is not an easy procedure.”

For more information:

Dawson C. Muir, MD, MBChB, FRACS, can be reached at Grace Orthopaedics Centre, Suite 3, 335 Cheyne Rd., Oropi 3112, Tauranga, New Zealand; 64 07 543 1850.

Michael J. Coughlin, MD, can be reached at 901 N. Curtis Rd., Suite 503, Boise, ID 83706; 208-377-1000; e-mail: margaret@coughlinmd.com. Neither source has any direct financial interest in any products or companies mentioned in this article.

Reference:

Muir D, McEntee L. A cautionary tale: The New Zealand experience of the Scandinavian Total Ankle Replacement. Presented at the 25th Annual Summer Meeting of the American Orthopaedic Foot and Ankle Society. July 15-18, 2009. Vancouver, British Columbia.