Functional Range of Motion Following Total Ankle Replacement

Abstract

Category: Ankle Introduction/Purpose: Total ankle replacement (TAR) is an accepted option for the surgical treatment of end-stage ankle arthritis. The potential benefit of TAR over ankle arthrodesis is the preservation of motion following TAR, however, little is reported concerning the true gain of range of motion (ROM) following TAR. This study compares standard goniometric measurements with two radiographic measurement techniques, as well as reports the changes in ROM following TAR. Methods: Between 2007 and 2012, 48 TAR in 46 patients were performed by a single surgeon, using a modern, fixed-bearing design. 40 patients (19 female, 21 male) had complete clinical and radiographic follow-up greater than 2 years postoperatively. Mean age at surgery was 73 +/- 9 years. Patients were evaluated with pre-operative and 2 year post-operative goniometric weight- bearing exam, as well as plantarflexion (PF) and dorsiflexion (DF) lateral radiographs. Radiographs were analyzed using the talocrural method, which measures the angle between the long axis of the tibia and talus, as well as a “full foot” method, which utilizes the angle created by the long axis of the tibia and medial cuneiform. The difference between the PF and DF angles was considered the arc ROM. Means were compared using a Wilcoxon signed-rank test to evaluate the significance of the difference between means (p < 0.05) Results: Mean arc range of motion increased from pre-operatively to post-operatively for all methods analyzed. Goniometric arc ROM significantly increased from 27.1° +/- 9.4° to 39.6° +/- 14.0°, a difference of 12.5° +/- 13.6° (p< .001). Talocural arc ROM significantly increased from 22.7° =/- 11.9° to 27. 8° +/- 10.2°, a difference of 5.1° +/- 11.2° (p=.006). Full foot arc ROM increased, but not significantly, from 46.7° +/- 15.5° to 48.8° +/- 12.6°, a difference of 2.6° +/- 11.2° (p=0.154). There was no significant difference observed between the mean gain in arc ROM between the two radiographic measurements (p=.062). However, the mean gain in arc ROM for goniometry significantly differed from both the talocural and full foot radiographic methods (p=.012 and p= .001, respectively). Conclusion: In this study, goniometry measurements tended to overestimate motion gained following TAR when compared to 2 radiographic measurement techniques. Interestingly, the talocrural method, which evaluates the ankle in isolation, was almost double the motion noted with the full foot method (5.1° vs. 2.6°) The full foot method may take into consideration the compensatory changes through the hindfoot and midfoot to account for ankle arthritis, that is alleviated post-TAR, hence, more modest gains in “full foot” arc ROM.