Development of the Foot and Ankle Activity Level Scale (FAALS) Instrument.

Abstract

Background: Activity level is a benchmark to document patient recovery; however, there is a lack of instrumentation to measure activity level specific to the foot and ankle. The purpose of this study was to develop a foot and ankle activity level scale (FAALS) instrument that will serve as an effective clinical tool for practitioners by assigning an activity level to patients.

Methods: This was a 4-phase study with 3 rounds of data collection (n = 1432). Phase 1 was item generation using an expert panel to determine content validity (101 items). In phase 2, all items from phase 1 were piloted (n = 100) to remove poorly performing items (77 items). In phase 3 (n = 505), item reduction, reliability, and validity Rasch analyses were conducted, leaving a total of 22 items. Validity was assessed using outfit mean-square (MNSQ) and infit MNSQ statistics, with acceptable values between 0.5 and 1.5. An additional round of data collection was completed to serve as a validation data set to confirm FAALS instrument structure and psychometric analytics (n = 827). Correlation analysis was performed to assess convergent and divergent validity. Multiple linear regression analysis was conducted to determine whether the FAALS could detect differences in scores between groups with previously proven factors that affect functional status.

Results: Person reliability was 0.92 and item reliability was 1.00, demonstrating excellent reliability. There was excellent evidence of validity, with mean-square values between 0.5 and 1.5. The 22 FAALS items are summed for a total score that corresponds to one of 4 activity levels. The FAALS instrument demonstrated sensitivity in the ability to discern between groups with expected foot and ankle functional differences for previous ankle surgery status, t(502) = -7.69, P < .001, and body mass index, t(502) = -3.41, P < .001.

Conclusion: The FAALS instrument is a short, clinically useful tool to measure activity level specific to the foot and ankle. FAALS normative values provide valuable information for physician-patient communication, which may serve to facilitate shared decision-making, improve postoperative care, and allow physicians to track recovery progress.