AOFAS 2008 Specialty Day explored the treatment of end-stage ankle arthritis

“Significant uncertainty exists about the proper role of ankle arthroplasty in the treatment of ankle arthritis,” said Nelson Fong SooHoo, MD, of the UCLA Center for Surgical Outcomes and Quality, who presented the results of a study comparing the reoperation rates of ankle arthrodesis and ankle replacement (Fig. 1) during the American Orthopaedic Foot and Ankle Society’s (AOFAS) 2008 Specialty Day program.

“Ankle fusion has been the traditional treatment,” said Dr. SooHoo, “and we’ve seen good functional outcomes. But concerns about adjacent joint arthritis have triggered an ongoing interest in ankle arthroplasty.”

Joint replacement increases risk of revision surgery
The study that Dr. SooHoo performed with Clifford Ko, MD, MSHS, and David Zingmond, MD, PhD, compared the reoperation rates of ankle arthrodesis and ankle replacement using observational, population-based data gathered from California’s discharge database on all inpatient admissions from 1994-2005. The researchers hypothesized that patients who had ankle replacement would have a lower risk of subtalar fusion but a higher overall risk of major revision surgery.

A total of 4,705 ankle fusions and 480 ankle replacements were performed during the 10-year study period. Dr. SooHoo and his colleagues found that ankle replacement patients had an increased risk of device-related infection and major revision procedures. Major revision surgery rates for ankle replacement patients were 9 percent at 1 year and 23 percent at 5 years, compared to 5 percent at 1 year and 11 percent at 5 years for ankle arthrodesis patients. Subtalar fusion, however, was more common among ankle arthrodesis patients (2.8 percent) than among ankle replacement patients (0.7 percent) at 5 years.

Using regression analysis, the researchers confirmed a statistically significant increase in the risk for major revision surgery among ankle replacement patients (hazard ratio 1.93, p<0.001) but a decreased risk of subtalar fusion (hazard ratio 0.28, p="0.03)" compared to ankle fusion patients.>

Patient populations, indications differ
Dr. SooHoo pointed out that the population of patients who underwent ankle arthroplasty may not be comparable with the one that underwent ankle arthrodesis. In addition, because the indications for ankle replacement differ substantially from those for arthrodesis, direct comparison of both the demographics and outcomes of these procedures may not be appropriate.

“It is likely that comorbidities such as ankle instability, bone loss, and deformity were more common in the ankle arthrodesis group,” said Dr. SooHoo. “Our study was unable to account for these differences between the patient populations, and our results may underestimate the increase in the rates of complications for arthroplasty relative to those associated with arthrodesis.”

“In addition,” explained Dr. SooHoo, “subtalar arthritis is a potential contraindication for ankle arthroplasty, which may account for the higher rate of subtalar fusion in the arthrodesis group and may have resulted in an overestimation in our study of the contribution of ankle fusion to subtalar pathology.”

Dr. SooHoo also noted that limited types of data are available in administrative databases such as the one used in the study, and data on functional outcomes are not available.

According to the researchers, controlled trials must be conducted to clarify the appropriate indications for ankle arthrodesis and ankle replacement.

“We hope that this information acts as a bridge between the small, clinical series that are currently available and larger, longer-term clinical trials,” said Dr. SooHoo.

Disclosure information for Dr. SooHoo and co-authors can be found online at www.aaos.org/disclosure

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org