E-mail this article to a friend  Download this article in PDF format

Fixed-bearing TAR improves gait function

By Terry Stanton

Gait study shows positive short-term results

A study of gait mechanics in patients who underwent total ankle replacement (TAR) with fixed-bearing implants found improvements in pain, gait, and function through 2 years postoperatively, while ankle range of motion was maintained.

The study, by Robin M. Queen, PhD, and his associates at the Michael W. Krzyzewski Human Performance Research Laboratory, Duke University Medical Center, was presented at the American Orthopaedic Foot & Ankle Society (AOFAS) 2011 annual meeting and received the J. Leonard Goldner Award for best research paper.

Although recent literature examining the newest generation of TAR prostheses almost exclusively addresses mobile-bearing implants not available in the United States, this study evaluated two different fixed-bearing TAR prostheses in 51 patients (27 male, 24 female; mean age at surgery, 65 years). Patients showed significant improvement in nearly all measured parameters of gait mechanics (measured preoperatively, 1 year postoperative, and 2 years postoperative) and maintained ankle range of motion as intended without significant differences between the two implant types.

In addition, pain was reduced and function improved from the preoperative baseline. None of the variables examined showed significant unfavorable changes following surgery. The study also found that gait changes at 1 year following TAR were maintained at least until the 2-year follow-up; in some cases, these changes continued to improve during the entire 2-year period.

Why use gait analysis?
Outcomes for TAR have been assessed using a variety of measures, including the following:

  • patient reported clinical outcomes
  • implant survival rates
  • radiographic evaluation of ankle alignment, bony interface, and implant migration
  • change in gait mechanics using motion capture

Only a few studies with limited numbers of patients have used gait analysis for an objective assessment of TAR functional outcomes.

According to the authors, improvements in spatial temporal variables—such as surgical-side single-leg support time, double-leg support time, stride length, stride width, and walking speed—most likely result from a reduction in pain and an increase in stability and balance. For example, preoperative pain causes subjects to shift weight away from the osteoarthritic ankle, decreasing single-leg support time and increasing double-leg support time. With less pain following TAR, patients were able to decrease their dependence on double-leg support and increase surgical-side single-leg support time.

Similarly, a decrease in ankle pain may also enable patients to take longer strides, because the ankle can absorb a greater impact without pain. Furthermore, the narrowing of the patients’ stride width reflected a reduced need for a wider, more stable base of support. Thus, these changes in spatiotemporal parameters of gait reflect the patients’ greater sense of stability and decreased joint pain while walking.

Limitations of the study include the use of only three surgeons to perform the TAR procedures. Also, the study group did not include all patients who received a fixed-bearing TAR, because some patients had confounding comorbidities and those who incurred complications were excluded. Finally, concerns have been raised about the validity of the AOFAS-Hindfoot Scale, although the authors say they believe the score is a useful comparative tool.

Co-authors of “Changes in Pain, Function and Gait Mechanics Two Years Following Total Ankle Arthroplasty Performed with Two Modern Fixed-Bearing Prostheses” are Justin C. De Biasio, BA; Robert J. Butler, DPT, PhD; James K. DeOrio, MD; Mark E. Easley, MD; and James A. Nunley, MD.

Disclosure information: Dr. Queen—DJ Orthopaedics, Foot and Ankle International; Dr. DeOrio—BioPro, Wright Medical Technology, Synthes, Arthrex; Dr. Easley—Small Bone Innovations (SBI), Saunders/Mosby-Elsevier; Wolters Kluwer Health, Lippincott Williams & Wilkins; Dr. Nunley—Wright Medical Technology ,SBI, Exactech, Stryker, Integra Life Sciences, Bristol Myers-Squibb, Merck, Johnson & Johnson, Orthopaedic Research and Education Foundation, Pfizer, DePuy, Arthrex, Springer, Datatrace. Dr. Butler and Mr. De Biasio reported no conflicts.

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

  • Current literature on the new generation of fixed-bearing TAR implants is not extensive.
  • In this study, patients receiving one of two types of fixed-bearing implants showed improvement in pain, gait, and function 2 years after surgery.
  • Improvements in gait spatiotemporal variables are likely the result of reduction in pain and an increase in stability and balance.

AAOS Now
September 2011 Issue
http://www.aaos.org/news/aaosnow/sep11/clinical6.asp