AOFAS announces results of clinical trials with the STAR ankle replacement device

Charles L. Saltzman, MD, newly-elected president of the American Orthopaedic Foot & Ankle Society (AOFAS), presented the results of a groundbreaking study at the recent AOFAS 2009 Annual Summer Meeting in Vancouver, British Columbia, Canada. This 24 month non-randomized clinical trial was conducted at 15 equivalent medical institutions offering a broad spectrum of surgical experience and is the first clinical study of its kind in the United States of the Scandinavian Total Ankle Replacement (STAR). After 24 months, the ankles treated with STAR ankle replacement had better function and equivalent pain relief as ankles treated with ankle fusion surgery. The study was published in the July 2009 issue of the Foot & Ankle International (FAI), the official journal of the AOFAS and also won the prestigious Roger A. Mann Award for best clinical paper presented at the meeting.

The STAR is unique because it is an uncemented, mobile-bearing total ankle replacement (TAR) device which is new in this country, although mobile-bearing ankle replacements have become popular outside the United States over the past decade. The goal of this study was to perform a prospective evaluation of the safety and efficacy of a mobile-bearing prosthesis to treat end-stage ankle arthritis and was approved as part of the investigational device exemption (IDE) by the Food and Drug Administration (FDA). According to the study, current US estimates for degenerative ankle disease suggests greater than 50,000 new cases reported each year. According to corresponding author, Michael J. Coughlin, MD, "This is the first prospective comparison between total ankle arthroplasty (replacement) and ankle arthrodesis (fusion) regarding function following surgery. The STAR ankle won hands down."

The Pivotal study design was a non-inferiority study with ankle fusion as the control. In a non-inferiority study, the primary objective is to demonstrate that a new treatment is equivalent to a standard therapy with regard to a particular result while also having benefits for other clinical end points, thus making the new treatment an attractive option. Three groups of patients were used in the study: a group of 158 STAR total ankle patients and a control group of 66 ankle fusion patients (the Pivotal Study Groups) and a second group of 448 STAR patients (Continued Access Group), whose surgery was performed following the completion of enrollment in the Pivotal Study.

Results were reported up to 24 months following surgery. For a patient to be considered a success, four criteria had to be met:

-- A 40-point improvement in total Buechel-Pappas ankle score -- No device failures, revisions, or removals -- Radiographic success -- No major complications

Complete data at 24 months was available for 96% of the pivotal ankle replacements, 79% of the pivotal ankle fusions and 66% of the continued access ankle replacements. Complications and the need for follow-up surgery were more common in the pivotal ankle replacement group than the ankle fusion groups. However, the need for secondary surgery was cut by 50% in the continued access ankle replacement group compared to the pivotal ankle replacement group, likely due to increased experience by the surgeons involved and improved instrumentation. By the end of the 24 months, ankles treated with the STAR ankle replacement had better function and equivalent pain relief as ankles treated with fusion.

Dr. Coughlin said, "There is no question that the new design of total ankle replacements is a more anatomic design. It is not cemented and requires less bone resection demonstrating far more superior results than the ankle replacements implanted in the 1970s. We are continuing to follow the over 600 patients involved in the study and will speak to their experiences in future publications.

"The STAR ankle is intended for use in patients with degenerative traumatic and/or rheumatoid arthritis for which conservative measures are no longer successful. Ankle replacement should be reserved for those patients with severe pain and loss of function for which conservative measures are no longer effective."

SOURCE: AOFAS