Comparison of Self-Reported vs Objective Measures of Long-Term Community Ambulation in Lower Limb Prosthesis Users

OBJECTIVE: To determine normal variation in walking metrics in a population of lower limb amputees who use lower limb prostheses over a 6-month period and to provide a means to interpret clinically meaningful change in those community walking metrics. DESIGN: Prospective cohort study monitoring walking behavior and subjective and objective measures of activity. SETTING: Veterans Administration and university amputee clinics. PARTICIPANTS: 86 individuals with lower limb amputation who use protheses. INTERVENTIONS: StepWatch activity monitor tracked subjects’ walking for 24 weeks; Global Mobility Change Rating collected weekly. MAIN OUTCOME MEASURES: Association between change in Global Mobility Change Rating and change in any of the walking metrics. RESULTS: Walking metrics including step count, cadence, cadence variability, and walking distance in a population of lower limb prosthesis users were obtained. There was a high correlation in the walking metrics indicating higher function with higher functional classification level (K-levels) but also substantial overlap in all metrics and a very weak correlation between subject-reported activity level and objective measures of walking performance. CONCLUSION: The overlap in walking metrics with all K-levels demonstrates that no single metric measured by StepWatch can determine K-level with 100% accuracy. As previously demonstrated in other populations, subjects’ interpretations of their general activity level was inaccurate, regardless of their age or activity level. Objective measures of walking appear to provide a more accurate representation of patients’ activity levels in the community than self-report. Therefore, objective measures of walking are useful in supporting K-level determinations. However, clinicians cannot rely on a single metric to determine K-level.