title: Validation of the Foot and Ankle Outcome Score in adult acquired flatfoot deformity.
abstract: BACKGROUND
  The American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score has been under recent scrutiny. The Foot and Ankle Outcome Score (FAOS) is an alternative subjective survey, assessing outcomes in 5 subscales. It is validated for lateral ankle instability and hallux valgus patients. The aim of our study was to validate the FAOS for assessing outcomes in flexible adult acquired flatfoot deformity (AAFD).
  
  
  METHODS
  Patients from the authors' institution diagnosed with flexible AAFD from 2006 to 2011 were eligible for the study. In all, 126 patients who completed the FAOS and the Short-Form 12 (SF-12) on the same visit were included in the construct validity component. Correlation was deemed moderate if the Spearman's correlation coefficient was .4 to .7. Content validity was assessed in 63 patients by a questionnaire that asked patients to rate the relevance of each FAOS question, with a score of 2 or greater considered acceptable. Reliability was measured using intraclass correlation coefficients (ICCs) in 41 patients who completed a second FAOS survey. In 49 patients, preoperative and postoperative FAOS scores were compared to determine responsiveness.
  
  
  RESULTS
  All of the FAOS subscales demonstrated moderate correlation with 2 physical health related SF-12 domains. Mental health related domains showed poor correlation. Content validity was high for the Quality of Life (QoL; mean 2.26) and Sports/Recreation subscales (mean 2.12). All subscales exhibited very good test-retest reliability, with ICCs of .7 and above. Symptoms, QoL, pain, and daily activities (ADLs) were responsive to change in postoperative patients (P < .05).
  
  
  CONCLUSIONS
  This study has validated the FAOS for AAFD with acceptable construct and content validity, reliability, and responsiveness. Given its previous validation for patients with ankle instability and hallux valgus, the additional findings in this study support its use as an alternative to less reliable outcome surveys.
  
  
  METHODS
  Level II, prospective comparative study.
authors.affiliation: Foot and Ankle Service, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Sriniwasan B
authors.initials: SB
authors.lastname: Mani
authors.forename: Haydée C
authors.initials: HC
authors.lastname: Brown
authors.forename: Pallavi
authors.initials: P
authors.lastname: Nair
authors.forename: Lan
authors.initials: L
authors.lastname: Chen
authors.forename: Huong T
authors.initials: HT
authors.lastname: Do
authors.forename: Stephen
authors.initials: S
authors.lastname: Lyman
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Deland
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Ellis
mesh_terms: D000328:Adult; D005413:Flatfoot / Q000503:physiopathology* / Q000523:psychology* / Q000628:therapy; D006305:Health Status Indicators; D006801:Humans; D010146:Pain / Q000209:etiology; D011446:Prospective Studies; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
keywords: AOFAS; FAOS validation; adult acquired flatfoot deformity; clinical rating systems; outcome studies