title: Foot rotational effects on radiographic measures of lower limb alignment.
abstract: BACKGROUND
  Surgical planning of high tibial osteotomy (HTO) typically requires the measurement of lower limb alignment from standing anteroposterior radiographs. Although every effort is made to maintain a standardized patient position, factors such as pain or anatomic constraints may necessitate acquiring the radiograph in a less than optimal patient position. One such constraint is natural rotation of the feet with respect to the tibia. The purpose of the present study was to investigate the magnitude of the effect of foot rotation on radiographic measures of lower limb alignment.
  
  
  METHODS
  We analyzed 19 lower limbs from radiographs obtained from 10 people who reported to an orthopedic injuries clinic. Each patient was radiographed in 3 positions: 15 degrees of internal foot rotation, no foot rotation and 15 degrees of external foot rotation. We measured and compared the mechanical axis angle (hip-knee-ankle) and the mechanical axis deviation from each position.
  
  
  RESULTS
  Compared with the position with no foot rotation, internal foot rotation resulted in less measured varus alignment and less mechanical axis deviation from the knee joint centre, whereas external foot rotation produced greater measured varus alignment and increased mechanical axis deviation from the knee joint centre.
  
  
  CONCLUSIONS
  These results indicate that patient positioning is an important factor when measuring lower limb alignment from radiographs. As a result, special care must be taken when acquiring these radiographs for use in planning surgical procedures such as HTO.
authors.affiliation: Wolf Orthopaedic Biomechanics Laboratory, the Faculty of Health Sciences, University of Western Ontario, London. mhunt3@uwo.ca
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hunt
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Fowler
authors.forename: Trevor B
authors.initials: TB
authors.lastname: Birmingham
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Jenkyn
authors.forename: J Robert
authors.initials: JR
authors.lastname: Giffin
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D006801:Humans; D035002:Lower Extremity / Q000000981:diagnostic imaging*; D008875:Middle Aged; D010027:Osteotomy; D011187:Posture / Q000502:physiology*; D011859:Radiography; D012399:Rotation