title: "Angle to Be Corrected" in Preoperative Evaluation for Hallux Valgus Surgery: Analysis of a New Angular Measurement.
abstract: BACKGROUND
  The most common methods for assessing severity of hallux valgus deformity and the effects of an operative procedure are the angular measurements in weightbearing radiographs, specifically the hallux valgus angle and intermetatarsal angle (IMA). Our objective was to analyze the interobserver variability in hallux valgus patients of a new angle called the "angle to be corrected" (ATC), and to compare its capacity to differentiate between different deformities against IMA.
  
  
  METHODS
  We included 28 symptomatic hallux valgus patients with 48 weightbearing foot x-rays. Three trained observers measured the 1 to 2 IMA and the ATC. We then identified retrospectively 45 hallux valgus patients, which were divided into 3 operative technique groups having used the ATC as reference, and analyzed the capacity of the IMA to differentiate between them.
  
  
  RESULTS
  The IMA average value was 13.6 degrees, and there was a significant difference between observer 3 and observer 1 (P = .001). The average value for the ATC was 8.9 degrees, and there was no difference between observers. Both angles showed a high intraclass correlation. Regarding the capacity to differentiate between operative technique groups, the ATC was different between the 3 operative technique groups analyzed, but the IMA showed differences only between 2.
  
  
  CONCLUSIONS
  The ATC was at least as reliable as the intermetatarsal angle for hallux valgus angular measurements, showing a high intraclass correlation with no interobserver difference. It can be suggested that the ATC was better than the IMA to stratify hallux valgus patients when deciding between different operative treatments.
  
  
  METHODS
  Level III, comparative study.
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
authors.forename: Cristian
authors.initials: C
authors.lastname: Ortiz
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile pwagner@alemana.cl.
authors.forename: Pablo
authors.initials: P
authors.lastname: Wagner
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
authors.forename: Omar
authors.initials: O
authors.lastname: Vela
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
authors.forename: Daniel
authors.initials: D
authors.lastname: Fischman
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cavada
authors.affiliation: Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
authors.forename: Emilio
authors.initials: E
authors.lastname: Wagner
mesh_terms: D005260:Female; D006215:Hallux Valgus / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D008297:Male; D008682:Metatarsal Bones / Q000000981:diagnostic imaging; D008875:Middle Aged; D015588:Observer Variation; D011300:Preoperative Care
keywords: angle to be corrected; angular measurement; hallux valgus; interobserver reliability