title: Intraoperative Fluoroscopic Imaging to Treat Cam Deformities: Correlation With 3-Dimensional Computed Tomography.
abstract: BACKGROUND
  In the diagnosis and surgical treatment of cam-type femoroacetabular impingement (FAI), 3-dimensional (3D) imaging is the gold standard for detecting femoral head-neck junction malformations preoperatively. Intraoperative fluoroscopy is used by many surgeons to evaluate and verify adequate correction of the deformity.
  
  
  OBJECTIVE
  (1) To compare radial reformatted computed tomography (CT) scans with 6 defined intraoperative fluoroscopic views before surgical correction to determine whether fluoroscopy could adequately depict cam deformity, and (2) to define the influence of femoral version on the clock-face location of the maximum cam deformity on these views.
  
  
  METHODS
  Cohort study (diagnosis); Level of evidence, 2.
  
  
  METHODS
  A consecutive series of 50 hips (48 patients) that underwent arthroscopic treatment for symptomatic FAI by a single surgeon were analyzed. Each patient underwent a CT scan and 6 consistent intraoperative fluoroscopy views: 3 views in hip extension and 3 views in hip flexion of 50°. The alpha angles of each of the fluoroscopic images were compared with the radial reformatted CT using a 3D software program. Femoral version was also defined on CT studies. Statistical analysis was performed using the Student t test, with P < .05 defined as significant.
  
  
  RESULTS
  Fifty-two percent of patients were male, average age 28 years (range, 15-56 years). The maximum mean alpha angle on fluoroscopy was 65° (range, 37°-93°) and was located on the anteroposterior (AP) 30° external rotation (ER) fluoroscopy view. In comparison, the mean CT-derived maximum alpha angle was 67° and was located at 1:15 (P = .57). The mean clock-face positions of each of the fluoroscopy views (standardized to the right hip) were AP 30° internal rotation, 11:45; AP 0° (neutral) rotation, 12:30; AP 30° ER, 1:00; flexion/0° (neutral) rotation, 1:45; flexion/40° ER, 2:15; and flexion/60° ER, 2:45. Increased femoral anteversion (>20°) was associated with a significant change in the location of the maximum alpha angle (1:45 vs 1:15; P = .002).
  
  
  CONCLUSIONS
  The described 6 fluoroscopic views are very helpful in localization and visualization of the typical cam deformity from 11:45 to 2:45 and can be used to reliably confirm a complete intraoperative resection of cam-type deformity in most patients. These views correlate with preoperative 3D imaging and may be of even greater importance in the absence of preoperative 3D imaging.
authors.affiliation: Sports Medicine and Shoulder Service, University of Michigan, Ann Arbor, Michigan, USA orthodocjimross@gmail.com.
authors.forename: James R
authors.initials: JR
authors.lastname: Ross
authors.affiliation: Sports Medicine and Shoulder Service, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.affiliation: Minnesota Orthopedic Sports Medicine Institute at Twin Cities Orthopedics, Edina, Minnesota, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Stone
authors.affiliation: Sports Medicine and Shoulder Service, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sibilsky Enselman
authors.affiliation: Schulthess Klinik, Bern, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Leunig
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Kelly
authors.affiliation: Minnesota Orthopedic Sports Medicine Institute at Twin Cities Orthopedics, Edina, Minnesota, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Larson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*; D005269:Femur / Q000000981:diagnostic imaging; D005270:Femur Head / Q000000981:diagnostic imaging*; D005471:Fluoroscopy / Q000379:methods; D006615:Hip / Q000000981:diagnostic imaging; D006621:Hip Joint / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: cam lesion; computer modeling; femoroacetabular impingement; fluoroscopy; hip arthroscopy