title: Validity and reliability of hallux valgus angle measured on digital photographs.
abstract: METHODS
  Controlled laboratory study.
  
  
  OBJECTIVE
  To investigate the reliability and concurrent validity of photographic measurements of hallux valgus angle compared to radiographs as the criterion standard.
  
  
  BACKGROUND
  Clinical assessment of hallux valgus involves measuring alignment between the first toe and metatarsal on weight-bearing radiographs or visually grading the severity of deformity with categorical scales. Digital photographs offer a noninvasive method of measuring deformity on an exact scale; however, the validity of this technique has not previously been established.
  
  
  METHODS
  Thirty-eight subjects (30 female, 8 male) were examined (76 feet, 54 with hallux valgus). Computer software was used to measure hallux valgus angle from digital records of bilateral weight-bearing dorsoplantar foot radiographs and photographs. One examiner measured 76 feet on 2 occasions 2 weeks apart, and a second examiner measured 40 feet on a single occasion. Reliability was investigated by intraclass correlation coefficients and validity by 95% limits of agreement. The Pearson correlation coefficient was also calculated.
  
  
  RESULTS
  Intrarater and interrater reliability were very high (intraclass correlation coefficients greater than 0.96) and 95% limits of agreement between photographic and radiographic measurements were acceptable. Measurements from photographs and radiographs were also highly correlated (Pearson r = 0.96).
  
  
  CONCLUSIONS
  Digital photographic measurements of hallux valgus angle are reliable and have acceptable validity compared to weight-bearing radiographs. This method provides a convenient and precise tool in assessment of hallux valgus, while avoiding the cost and radiation exposure associated with radiographs.
authors.affiliation: Division of Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia.
authors.forename: Sheree
authors.initials: S
authors.lastname: Nix
authors.forename: Trevor
authors.initials: T
authors.lastname: Russell
authors.forename: Bill
authors.initials: B
authors.lastname: Vicenzino
authors.forename: Michelle
authors.initials: M
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006215:Hallux Valgus / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008682:Metatarsal Bones / Q000000981:diagnostic imaging; D008875:Middle Aged; D010781:Photography / Q000379:methods*; D011859:Radiography; D015203:Reproducibility of Results; D055815:Young Adult