By Hank Black
End-stage ankle arthritis patients who receive a newer-generation total joint implant function slightly but significantly better when walking on uneven surfaces than patients who undergo ankle arthrodesis, according to a recent prospective study.
Arthrodesis remains the gold standard for young and very active patients but, because total ankle arthroplasty (TAA) preserves ankle motion and improves walking function on level surfaces, it is receiving an increasing amount of consideration. Patients with ankle fusions also are at risk for joint degeneration in the adjacent subtalar area.
“There is a resurgence of interest in ankle replacement since the advent of the newest-generation of arthroplasty devices,” said James R. Jastifer, MD, an orthopedic surgeon now with Borgess Orthopedics in Kalamazoo, MI, and first author of the study. “Patients hear of the long-term success of knee and hip replacements and assume that ankle joints can be replaced just as effectively. Ankle replacement is more complicated in critical ways, but the new designs are improving.”
The study, epublished September 8 by Foot and Ankle International, was performed when Jastifer was at Saint Alphonsus Regional Medical Center’s Coughlin Foot & Ankle Clinic in Boise, ID.
The study used a low-profile ankle replacement system, the only three-part, noncemented, mobile-bearing implant approved by the US Food and Drug Administration for ankle arthroplasty. Jastifer noted that, along with improved design, newer implants also have benefited from advancements in surgical instrumentation and implant composition.
Previous studies had shown that both ankle replacement and ankle fusion improve gait (though not to normal) on flat surfaces and clinical range of motion compared to preoperative status, but patients report that functional activities of daily living, such as climbing stairs and walking on uneven surfaces, remain problematic, according to Jastifer. His group showed how TAA affects patients’ gait while walking on flat and uneven surfaces, up and down stairs, and up and down hill, and compared TAA patients to arthrodesis patients on the same surfaces.
“Patients undergoing TAA generally assume that their performance on other-than-flat surfaces would improve compared to preoperative values as well as compared to ankle fusion, but this had not previously been investigated,” he said.
For the study, participants self-selected either TAA or arthrodesis following an explanation of risks and benefits; 61 TAA patients and 16 arthrodesis patients were included in the final analysis. The mean age of the groups was similar, 65.2 years for the arthroplasty cohort and 60.2 years for the arthrodesis cohort. Evaluations were performed at six months preoperatively and at six and 12 months postoperatively.
Preoperative values were similar for both groups. At both postoperative time points, both cohorts had improved function on uneven surfaces, with the TAA group performing slightly but significantly better with regard to self-reported difficulty negotiating stairs and walking uphill, which Jastifer believes is due to preserved ankle motion. The TAA patients also had significantly greater improvement than the arthrodesis patients for ankle range of motion and several objective functional measures.
“The difference was not statistically significant in some cases, probably because our study was underpowered due to the smaller number of individuals in the fusion group, which was the result of our desire to ensure homogenous patient demographics,” Jastifer said. “We are now attempting to validate our outcome scale to determine what it means to be ‘slightly better,’ since there is no definition for measuring function on uneven ground.”
Professor Alastair Younger, MB, ChB, FRCSC, MSc, ChM, director of the Division of Distal Extremities at the University of British Columbia in Vancouver, Canada, said, “We have a lot of positive feedback from patients for TAA over fusion, but many outcome scales fail to capture the cause of the satisfaction, so this paper assists in demonstrating why ankle replacement may feel more normal than ankle fusion.”
The study may also help in the consent process and in justifying to insurers the additional cost of TAA over arthrodesis, said Younger, who has coauthored major papers comparing TAA and ankle arthrodesis.
Jastifer JR, Coughlin MJ, Hirose C. Performance of total ankle arthroplasty and ankle arthrodesis on uneven surfaces, stairs, and inclines: A prospective study. Foot Ankle Int 2014 Sep 8. [Epub ahead of print]