title: The sensitivity of standard radiographic foot measures to misalignment.
abstract: BACKGROUND
  The purpose of this study was to identify the effects that X-ray source misalignment has on common measurements made from anterior-poster (AP) and medial-lateral (ML) view foot radiographs.
  
  
  METHODS
  A cadaveric foot model was used to obtain ML radiographs with ±25 degree transverse plane misalignment. From these images the calcaneal pitch angle (CPA) and lateral talometatarsal angle (LTMA) were measured. AP images were captured with up to 30 degree sagittal plane misalignment as well as ±15 degree misalignment in the transverse plane at each sagittal angle. From these images the talonavicular coverage angle (TNCA) and talometatarsal angle (TMA) were measured.
  
  
  RESULTS
  On the ML images, the CPA was sensitive to transverse plane misalignment from -10 to -25 degrees and from 15 to 25 degrees (P < .005). The LTMA was a more reliable measurement than the CPA and did not demonstrate sensitivity to transverse plane misalignment. On the AP images, the TNCA and TMA were not sensitive to sagittal plane misalignment alone. However, at 0, 10, and 15 degrees sagittal misalignment the TNCA showed sensitivity to transverse plane misalignment (P < .0083).
  
  
  CONCLUSIONS
  Misalignment of an X-ray source can lead to errors in the measurement of foot radiographic parameters, especially the CPA when there is transverse plane misalignment and the TNCA when there is both sagittal and transverse plane misalignment. The LTMA and TMA can be measured reliably, even with significant misalignment present.
  
  
  CONCLUSIONS
  If a researcher or clinician is interested in measuring the CPA or TNCA, the current best practices guidelines for obtaining ML and AP images should be closely followed.
authors.affiliation: Department of Veterans Affairs, RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA, USA School of Medicine, University of Washington, Seattle, WA, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Willauer
authors.affiliation: Department of Veterans Affairs, RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA, USA Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, USA bsangeor@uw.edu.
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Sangeorzan
authors.affiliation: Department of Veterans Affairs, RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA, USA.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Whittaker
authors.affiliation: Department of Veterans Affairs, RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA, USA.
authors.forename: Jane B
authors.initials: JB
authors.lastname: Shofer
authors.affiliation: Department of Veterans Affairs, RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, Seattle, WA, USA Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, USA Department of Mechanical Engineering, University of Washington, Seattle, WA, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Ledoux
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017760:Bone Malalignment / Q000000981:diagnostic imaging*; D002102:Cadaver; D005260:Female; D005528:Foot / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography / Q000379:methods / Q000592:standards*; D012015:Reference Standards; D012680:Sensitivity and Specificity
keywords: X-ray; foot; misalignment; radiograph