Correlation of Functional Measures of Mobility with Patient-Reported Outcomes after Total Ankle Arthroplasty

Abstract

Category: Ankle Introduction/Purpose: Patients undergoing total ankle arthroplasty (TAA) have a proven track record of clinical improvements in subjective patient-reported outcome measures (PROMs) and objective measures with three dimensional gait analysis. Each represents a valid, but different kind of information, and both are important. What is unknown is whether and how objective improvements as measured by gait analysis correlate with the improvements measured by PROMs. The goal of this study was to investigate the correlation between objective function and PROMs in patients undergoing TAA. Methods: Seventy-six patients (28m/48f) aged 61 (37-79) with a mean BMI of 29.60 (19.63-46.64) and greater than 1-year follow-up underwent preoperative and postoperative gait analysis. Temporal-spatial, kinematic, and kinetic parameters of gait were recorded. Patients also completed AOFAS Ankle/Hindfoot scores, visual analog score for pain (VAS), and the MOS 36-Item Short-Form Health Survey (SF-36) questionnaires within two weeks of their preoperative gait analysis and at the one-year postoperative gait analysis. A t-test for dependent means was used to compare preoperative and postoperative outcomes. Additionally, a Pearson correlation coefficient was utilized to measure the strength of association between parameters of gait and PROMs. A p-value of < 0.05 was considered to be statistically significant. Results: Gait Analysis: Patients had a statistically significant improvement in all temporal-spatial parameters of gait, in total range of motion, mean maximum plantarflexion, and ankle power. Patient-reported outcome measures: A statistically significant and clinically meaningful significant improvement was detected for AOFAS score, VAS score, and SF-36-Physical score. Changes in the SF-36-Mental score were not detected to be statistically significant or clinically significant. Correlation: The AOFAS score had a moderate positive correlation with preoperative walking-speed, step-length and ankle-power, postoperative walking-speed, step-length and ankle-power, and improvement in walking-speed, cadence, and ankle-power. The SF-36-Physical score had a weak to moderate positive correlation with preoperative walking speed, step length, and ankle power and postoperative walking speed, step length and ankle power. No correlation between VAS or SF-36-Mental score and function could be detected. Conclusion: There is a moderate correlation with AOFAS and SF-36-Physical scores between walking speed (temporal-spatial parameters), and ankle push-off power (kinetic parameters). PROMs did not correlate with improvements in ROM (kinematic parameters). This may challenge the assumption that preservation of motion is the most important role of TAA. The data may be interpreted to mean cadence, walking-speed, step-length and ankle power are the most important aspects of gait with respect to patients’ perceived outcomes. However, perhaps ROM is important to patient satisfaction – but the outcome measures we use are not sufficiently sensitive/specific to measure the effect of improved or maintained motion.