July 2012

Fusion vs replacement: Both improve gait, but well short of normal

In the moment: Ankle

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By Jordana Bieze Foster

Functional outcomes for total ankle re­place­ment (TAR) in patients with end-stage ankle arthritis appear to match or exceed those of ankle fusion, according to research presented in June at the an­nual meeting of the American Ortho­paedic Foot & Ankle Society (AOFAS).

Given that most surgeons’ experience with TAR, or total ankle arthroplasty, has been acquired in just the last two decades, the results are encouraging. But surgeons remain frustrated by the sizeable functional gap that still separates both fusion patients and TAR patients from normal individuals.

“The differences between fusion and replacement are real and appreciated by the patient, I can assure you of that. But neither fusion nor replacement return gait to normal. We’re not even close,” said Timothy R. Daniels, MD, an associate professor of surgery and head of the Foot & Ankle Service at the University of Toronto in Ontario, Canada.

Daniels’ group has looked at the functional effects of TAR from two different perspectives, which have produced somewhat different results.

To examine the biomechanical effects, they performed gait analysis on 17 TAR patients and 17 fusion patients preoperatively and one year postoperatively and compared the gait variables to those of 10 healthy controls. They found that TAR patients had more total sagittal plane range of motion (ROM) and more dorsiflexion ROM at one year than the fusion group, but that plantar flexion ROM was similar. Ankle power was also 30% greater in the TAR patients than the fusion patients. Dorsiflexion ROM for the TAR group approached that of the controls, but plantar flexion ROM and power in the control group remained dramatically superior to both surgical groups.

The Toronto group also participated in a large multicenter study comparing 267 TAR procedures to 99 fusion procedures using questionnaire-based functional outcome measures. A mean of 4.5 years after surgery, preliminary results suggested a trend in favor of TAR for outcome scores on both the Ankle Osteoarthritis Scale and Short Form 36 measures. However, after adjusting for age and other baseline characteristics, there were no functional differences between groups that even approached significance.

“This is really a reflection of the beginnings of TAR in Canada so in many ways I was surprised that [the TAR group] did so well,” Daniels said.

Researchers from Baylor University found that gait-related improvements one year after surgery were similar for 14 TAR patients and 14 fusion patients. Postoperative velocity, cadence, and step length did not differ significantly between the groups. The TAR group demonstrated significantly more plantar flexion than the fusion group, and the fusion patients demonstrated significantly more coronal plane range of motion than their TAR counterparts; other kinematic and kinetic variables were similar for the two groups.

The improvements in the fusion group may be in part related to compensatory hypermobility in the transverse tarsal and midfoot joints, said Robert Flavin, an orthopedic surgeon at Cappagh National Orthopedic Hospital in Dublin, Ireland, who presented the Baylor findings at the AOFAS meeting.

A study from the VA Puget Sound in Seattle, published in the April issue of Foot & Ankle International, suggests another possible mechanism. One year after surgery, the Seattle researchers found that hip ROM was significantly greater in nine fusion patients than in nine TAR patients; ankle ROM was significantly greater in the TAR patients. Gait velocity and stride length were similar in both groups.

Sources:
Singer SB, Klejman S, Pinsker E, et al. Ankle arthroplasty and ankle arthro­desis–prospective gait analysis com­pared to controls. Presented at the American Orthopaedic Foot & Ankle Society Annual Meeting, San Diego, June 2012.

Daniels TR, Glazebrook MA, Penner MJ, et al. COFAS multicenter study comparing total ankle arthroplasty and ankle arthrodesis: mid-term results. Presented at the American Orthopaedic Foot & Ankle Society Annual Meeting, San Diego, June 2012.

Flavin R, Coleman S, Brodsky JW. Comparison of effect on gait of total ankle arthroplasty vs ankle fusion. Presented at the American Orthopaedic Foot & Ankle Society Annual Meeting, San Diego, June 2012.

Hahn ME, Wright ES, Segal AD, et al. Comparative gait analysis of ankle arthrodesis and arthroplasty: initial findings of a prospective study. Foot Ankle Int 2012;33(4):282-289.

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