title: Femoral rotation unpredictably affects radiographic anatomical lateral distal femoral angle measurements.
abstract: OBJECTIVE
  To describe the effects of internal and external femoral rotation on radiographic measurements of the anatomical lateral distal femoral angle (a-LDFA) using two methods for defining the anatomical proximal femoral axis (a-PFA).
  
  
  METHODS
  Digital radiographs were obtained of 14 right femora at five degree intervals from 10° external rotation to 10° internal rotation. Using freely available software, a-LDFA measurements were made using two different a-PFA by a single observer on one occasion.
  
  
  RESULTS
  Mean a-LDFA was significantly greater at 10° external rotation than at any other rotation. The response of individual femora to rotation was unpredictable, although fairly stable within ±5° of zero rotation. Mean a-LDFA for the two a-PFA methods differed by 1.5°, but were otherwise similarly affected by femoral rotation.
  
  
  CONCLUSIONS
  If zero femoral elevation can be achieved for radiography, a-LDFA measurements do not vary much with mild femoral rotation (±5°). Outside of this range, a-LDFA varies unpredictably with femoral rotation.
authors.affiliation: James E. Miles, Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 16, 1870 Frederiksberg C, Denmark, Phone: +45 2057 0840, Fax: +45 3533 2929, E-mail: jami@sund.ku.dk.
authors.forename: James E
authors.initials: JE
authors.lastname: Miles
mesh_terms: D000818:Animals; D004285:Dogs / Q000033:anatomy & histology*; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D011859:Radiography; D012399:Rotation
keywords: Femur; canine; radiography; varus