title: Intraoperative assessment of closed reduction for developmental dislocation of the hip using 3-dimensional fluoroscopy.
abstract: BACKGROUND
  Postoperative imaging for operatively treated developmental dislocation of the hip typically uses computed tomography or a magnetic resonance imaging (MRI). Neither imaging modality offers the ability to intervene intraoperatively. The 3-dimensional (3D) C-arm provides an attractive alternative providing immediate intraoperative feedback on the quality of a hip reduction. Our primary research question was to determine whether 3D fluoroscopy could assess hip position after closed reduction and spica casting. Secondary questions included whether reduction was maintained postoperatively when compared with postoperative MRI, and to determine the radiation dose received by the infant.
  
  
  METHODS
  We retrospectively identified 16 patients from 2010 to 2013 who underwent closed reduction and spica casting for a developmentally dislocated hip who underwent both intraoperative 3D fluoroscopy and postoperative MRI imaging. Scans were retrieved and assessed by a blinded pediatric orthopaedic fellow. Assessment of hip reduction was graded based on the modified Shenton line of the pelvis in axial plane images. Effective radiation doses between imaging modalities were compared using an anthropomorphic phantom.
  
  
  RESULTS
  All hips were reduced on 3D fluoroscopic images. Comparing the intraoperative 3D scans with the postoperative MRI images all 16 hips were in the same position. At 12 weeks all hips were reduced and no signs of subluxation were identified on the plain anteroposterior radiograph. 3D fluoroscopy achieved the lowest effective dose of radiation per study measuring 0.3 mSv compared with 0.5 mSv for low-dose CT and 0.48 mSv for 60 seconds of live fluoroscopy.
  
  
  CONCLUSIONS
  Accurate assessment of the quality of hip reduction is possible in the axial plane using 3D fluoroscopy with no significant loss of reduction in the early postoperative period. When comparing the effective radiation exposure to limited-cut computed tomography protocols, 3D fluoroscopy offers a low-dose alternative that may facilitate cost savings and early discharge.
  
  
  METHODS
  Diagnostic studies-investigating a diagnostic test; study of nonconsecutive patients with consistently applied gold standard; level III.
authors.affiliation: *Department of Surgery, University of Toronto †Division of Orthopaedics, The Hospital for Sick Children ‡Advisory Council, SickKids International, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Brant
authors.initials: B
authors.lastname: Sachleben
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Perry
authors.forename: John
authors.initials: J
authors.lastname: Wedge
authors.forename: Simon P
authors.initials: SP
authors.lastname: Kelley
mesh_terms: D002370:Casts, Surgical; D005260:Female; D005471:Fluoroscopy / Q000379:methods*; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging* / Q000628:therapy*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008349:Manipulation, Orthopedic; D011829:Radiation Dosage; D012189:Retrospective Studies