Patient Reported Outcome Measures in the Foot and Ankle: Normative Values Do Not Reflect 100% Full Function

Purpose: The primary purpose of this study was to determine normative values for foot and ankle ability measure (FAAM), activities of daily living (ADL), FAAM/foot and ankle disability (FADI) Sport, Tegner activity scale, SF-12 physical component summary (PCS) and mental component summary (MCS) in individuals who are representative of the "normal" adult population in the United States. The secondary purpose was to perform a confirmatory factor analysis (CFA) of ankle functional ability to provide evidence of reliability and validity of commonly used orthopaedic outcome scores. Our hypothesis was that normative values will differ based on patient characteristics and demographics, and that the selected commonly used foot and ankle outcomes scores will demonstrate acceptable reliability and validity estimates.

Methods: There were 271 persons in this study (101 women, 170 men, average age = 31.4 (SD = 15.1) years, average BMI = 25.9 (SD = 5.9)). Age, sex and BMI were documented. Comparisons of outcome scores were made between cohorts. CFA was performed to test factor structure of ankle functional ability.

Results: There was no significant difference in FAAM ADL between women and men (n.s.) or FAAM Sport (n.s.). Women had significantly higher SF-12 PCS (P = 0.001). Men had significantly higher SF-12 MCS (P < 0.001) and Tegner (P = 0.024). FAAM ADL, FAAM Sport and SF-12 PCS scores were significantly higher in people who did not have previous ankle surgery. Younger people and those with lower BMI had significantly higher ankle function. Reliability was excellent, and the CFA had excellent model fit demonstrating evidence of validity.

Conclusions: This study revealed that normative values of foot and ankle outcome measures did not reflect 100% function and differed by sex, previous ankle surgery status, age and BMI. Individuals who did not have previous ankle surgery were younger, and had lower BMI and higher functional levels. Reliability was excellent, and the CFA model demonstrated excellent fit, providing evidence for validity, and lending support to use aggregated outcome measures as one scale. This study is unique in that it provides surgeons with normative ankle values in commonly reported outcome measures including the FAAM, FADI SF-12 and Tegner activity scale, in the normal population, based on BMI, age, gender and previous ankle surgery status. This information can be a very useful tool in the clinical setting for patient expectations counseling. In addition, surgeons and clinicians can feel confident using these outcome scores to assess their patients' progress through the continuum of care.

Level Of Evidence: Level II.