Study Questions Benefit of TAR Compared with AA

Phil Vinall

doi:10.1177/155989771434005

Summary

This article discusses results from a study that examined functional outcomes among patients treated with total ankle replacement, ankle arthrodesis, or tibiotalocalcaneal ankle fusion and healthy controls under 3 conditions: barefoot, wearing standardized running shoes, or wearing standardized rocker-bottom shoes.

Foot & Ankle Conditions
Orthopaedic Procedures
Orthopaedics Clinical Trials

Foot & Ankle Conditions
Orthopaedic Procedures
Orthopaedics
Orthopaedics Clinical Trials

Arno Frigg, MD, University Hospital Basel, Basel, Switzerland, reported results from a study that examined functional outcomes among patients treated with total ankle replacement (TAR), ankle arthrodesis (AA), or tibiotalocalcaneal (TTC) ankle fusion and healthy controls under 3 conditions: barefoot, wearing standardized running shoes, or wearing standardized rocker-bottom shoes. The study showed no difference in functional outcomes among patients treated with TAR or AA. Patients treated with TTC ankle fusion had inferior results in all conditions.

The study included 126 postsurgical patients (28 who received TAR, 57 who received AA, and 41 who had undergone TTC ankle fusion) and 35 healthy volunteers. Clinical evaluation was based on American Orthopaedic Foot & Ankle Score and Short Form-36 scores, radiographs, and postoperative complications. Patient follow-up was a mean of 4.1 years (range, 2 to 6 years). Functional evaluation was based on the results of dynamic pedobarography [Frigg A et al. Clin Biomech (Bristol, Avon). 2012] and a light gate. The primary outcome measures were the following: walking speed, maximal force (MF) in the forefoot, and relative midfoot index (rMI), a measure of the relative difference in MF between the average of the hindfoot and forefoot and the midfoot (ie, the extent of the mid-foot's MF depression).

There was no significant difference in walking speed between TAR and AA whether patients were barefoot or wore running shoes or rocker-bottom shoes (P = .52 to .62). Both were walking significantly slower by about 0.3 m/s compared with healthy controls (P < .01) in any condition. Patients treated with TTC ankle fusion were significantly slower than the other groups in all conditions (P < .05; Figure 1).

Figure 1.

Walking Speed Results

AA, ankle arthrodesis; TAR, total ankle replacement; TTC, tibiotalocalcaneal.Reproduced with permission from A Frigg, MD.

Relative to healthy controls, the TAR and AA groups had an increased forefoot MF regardless of whether the patients were barefoot or were wearing running shoes or rocker-bottom shoes; the differences were not significant (P = .07 to .86). There was no significant difference in forefoot MF between patients treated with TAR or AA in any of the conditions (P = .7 to .9). Patients treated with TTC ankle fusion had results that were inferior to those of both TAR and AA (Figure 2).

Figure 2.

Forefront Maximal Force Results

AA, ankle arthrodesis; TAR, total ankle replacement; TTC, tibiotalocalcaneal.Reproduced with permission from A Frigg, MD.

In patients who were barefoot, rMI was significantly smaller with the TAR and AA groups, relative to healthy controls (P < .01), but not significantly different between TAR and AA (P = .35). In running shoes, there was no difference between TAR and AA, but there was a significant difference compared with healthy controls (P < .05). In rocker-bottom shoes, there were no significant group differences (P = .48). TTC ankle fusion was associated with a significantly smaller rMI in all conditions compared with the other groups (P < .001; Figure 3).

Figure 3.

Relative Midfoot Index Results

AA, ankle arthrodesis; TAR, total ankle replacement; TTC, tibiotalocalcaneal.Reproduced with permission from A Frigg, MD.

This study found no measurable difference in running shoes or rocker-bottom shoes between patients treated with TAR and AA. In addition, an increased forefront MF that might be a trigger for adjacent osteoarthritis was not found in patients treated with AA compared with those treated with TAR. Patients treated with TTC ankle fusion have an inferior functional outcome.

Prof. Frigg questioned whether there was any benefit for TAR over AA considering TAR's high rates of failure [Henricson A et al. Acta Orthop. 2011] and revision [SooHoo NF et al. J Bone Joint Surg Am. 2007] compared with AA.

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