Background: The decision tree for the operative treatment of end-stage ankle arthritis involves either ankle arthrodesis (AA) or total ankle arthroplasty (TAA). Although both have documented success providing diminished pain, improved patient-centered outcomes, and improved objective measures of function, arthroplasty is unique in its ability to preserve motion at the tibiotalar joint. Arthroplasty procedures are normally thought of as a motion-sparing surgery rather than a motion-producing procedure, which may limit its success in patients with stiff ankles. Our hypothesis was that there would be improvements in parameters of gait even in patients with a low degree of preoperative total sagittal range of motion.
Methods: A retrospective review was conducted on patients who underwent total ankle arthroplasty with greater than 1-year follow-up. Seventy-six patients were available who underwent isolated TAA for end-stage ankle arthritis with greater than 1-year follow-up. Patient demographics and preoperative and postoperative gait analyses were evaluated. Using a linear regression model, the effect sizes for the variables of age, gender, BMI, preoperative diagnosis, and preoperative total sagittal range of motion were calculated. Multivariate analysis was used to determine the influence each individual variable had on the many parameters of preoperative gait, postoperative gait, and change in gait after surgery. A post hoc analysis was conducted in which patients were divided into 4 quartiles according to preoperative range of motion. A 1-way analysis of variance (ANOVA) was used to compare improvement in parameters of gait for the 4 subgroups.
Results: Although a greater degree of preoperative sagittal range of motion was predictive of greater postoperative sagittal range of motion, patients with limited preoperative range of motion experienced a greater overall improvement in range of motion, and clinically meaningful absolute improvements in range of motion, and other parameters of gait. The post hoc analysis demonstrated that patients in the lowest quartile of preoperative motion had both statistically and clinically significant greater improvements across numerous parameters of gait, although the absolute values were lower than in the patients with higher preoperative ROM. Age, gender, BMI, and preoperative diagnosis did not correlate with changes in parameters of gait after total ankle arthroplasty.
Conclusion: Preoperative range of motion was predictive of overall postoperative gait function. On one hand, a low preoperative range of motion resulted in a lower absolute postoperative function. On the other hand, patients with stiff ankles preoperatively had a statistically and clinically greater improvement in function as measured by multiple parameters of gait. This suggests that total ankle arthroplasty can offer clinically meaningful improvement in gait function and should be considered for patients with end-stage tibiotalar arthritis even in the setting of limited sagittal range of motion.
Level of evidence: Level IV, retrospective case series.
Keywords: ankle arthritis; arthroplasty; gait studies; outcome studies.