Role of Total Ankle Arthroplasty in Stiff Ankles – Long Term Follow-Up

Abstract

Category: Ankle, Ankle Arthritis Introduction/Purpose: Operative treatment of end-stage ankle arthritis involves either ankle arthrodesis (AA) or total ankle arthroplasty (TAA). The theoretical benefit of TAA is the ability to preserve range of motion (ROM) at the tibiotalar joint. Previous studies have questioned whether it is justified to perform TAA over AA in stiff, arthritic ankles. However, a recent study showed that patients who underwent TAA with stiff ankles preoperatively experienced significant clinical improvement in range of motion and gait function compared to more flexible groups at 1-year follow-up. We retrospectively assessed these same gait and functional parameters to see if these improvements held up in long-term follow-up. Methods: A retrospective study of long-term, prospectively collected functional gait data in 33 TAA patients at a mean of 7.6 years postoperatively (range 4.8-13.3) used a multivariate regression model to determine the effect of ankle stiffness on the long- term, objective outcomes of TAA. Data was analyzed by quartiles (Q1, Q2+Q3, Q4) of preoperative sagittal ROM using one-way analysis of variance (ANOVA) to compare both preop and postop gait parameters. The two middle quartiles were combined to conform to distribution of the data. The multivariate analysis determined the independent effect of age, gender, BMI, years post- surgery, and preop ROM on every preop and postop parameter of gait. Results: Statistically significant differences were found in all three gait parameter categories, including temporal-spatial (step length and walking speed), kinematic (total sagittal ROM and maximum plantarflexion), and kinetic (peak ankle power). The stiffest ankles preoperatively (Q1) had the greatest absolute increase in total sagittal ROM postoperatively, +5.3o, compared to -1.3o (p<0.0174) in Q4 (most flexible). However, Q1 had the lowest absolute total postoperative sagittal ROM of 13.1 o, compared to 19.7 o (p<0.0108) in Q4. Q1 also had the lowest preoperative step length, walking speed, maximal plantarflexion, and peak ankle power when compared to the other subgroups. There was no difference in any of these same parameters postoperatively. BMI and years post-surgery had no effect on outcomes, while age and gender had a minimal effect. Conclusion: Preoperative range of motion was once again predictive of overall postoperative gait function in long-term follow-up at an average of 7.2 years. A greater degree of preoperative sagittal range of motion was predictive of greater postoperative sagittal range of motion in long-term follow-up. Patients with the stiffest ankles preoperatively once again had a statistically and clinically greater improvement in function as measured by multiple parameters of gait. This shows that the clinically meaningful improvement in gait function after total ankle arthroplasty holds up in long-term follow-up, even in the setting of limited preoperative sagittal range of motion.