Normative Values for Commonly Reported Outcome Measures in the Foot and Ankle

Abstract

Category: Ankle Introduction/Purpose: There has been increased attention regarding normative values for patient reported outcomes. Differences in population demographics and factors such as previous surgery, could influence functional improvement, obfuscating generalizability among previous studies. To determine realistic patient outcomes, it is important to establish normative values for commonly reported foot and ankle outcome measures, while accounting for population effects. The primary purpose of this study was to determine normative values for the Foot and Ankle Ability Measure(FAAM) Activities of Daily Living(ADL) subscale, FAAM Sport subscale, Tegner activity scale, and 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(US). Methods: This study was approved by an institutional review board. The target population was adults, >18 years old, in the “normal” population. Normal was defined as previously done by AAOS, which is the random sample of individuals from the general US population. Individuals were only excluded if younger than 18 years old. There were 271 people in this study (101 females, 170 males) with an average age of 31.4 (SD=15.1; range 18–77) years. Average BMI was 25.9 (SD=5.9; range 16.5–44.9). The questionnaire included demographics: age, sex and BMI and outcome measures: FAAM ADL, FAAM Sport, Tegner and SF-12 PCS and MCS. Mean outcome scores were determined for each cohort and tested for differences in each variable of interest using analysis of variance (ANOVA) and independent t-tests. Results: The average FAAM ADL was 92.3 (SD=12.3; range 32.1–100.0). The average FAAM Sport was 85.1 (SD=20.2; range 0.0– 100.0). The average SF-12 PCS was 48.6 (SD=8.2; range 20.2–64.1). The average SF-12 MCS was 47.6 (SD=11.0; range 17.2–65.1). Median Tegner was 4 (SD=2.1; range 0–10). There was no significant difference in FAAM ADL between females and males(P=.256) or FAAM Sport(P=.050). Females had significantly higher SF-12 PCS(P=.001). Males had significantly higher SF-12 MCS(P<.001) and Tegner(P=.024). FAAM ADL, FAAM Sport and SF-12 PCS scores were significantly higher in people who did not have previous ankle surgery. Younger people with lower BMI values tended to have significantly higher ankle function. Conclusion: Normative values of foot and ankle outcome measures differed by sex, previous ankle surgery, age and BMI. Younger individuals, with lower BMI, with no previous ankle surgery, had higher functional and activity levels. Males had significantly higher activity levels and mental health. Females had significantly greater general health. Average outcomes in the normal population did not reflect 100% for each score, but rather somewhat less. This information is valuable for patient expectations counseling. With normative data serving as a reference, physicians can assess whether baseline measurements differ from population norms, and whether patients have returned to “normal” levels following treatment.