title: Proposed Referential Index to Resect Femoroacetabular Cam-Type Impingement During Arthroscopy Using a Cadaveric Hip Model.
abstract: OBJECTIVE
  To establish a reference index for the simple identification of the optimum resection point for cam-type impingement on arthroscopy.
  
  
  METHODS
  Twelve cadaveric left hips with a 20° to 40° center-edge angle, without osteoarthritis, were examined (mean age, 85 ± 10.1 years). The pelvis was fixed such that the anterior pelvic plane and femur were parallel to the table. The resection line for impingement was first defined on the femoral head surface 5 mm distal to the acetabular labrum, from the 9-o'clock (anterior) to 12-o'clock (superior) position. Next, we measured the hip flexion angle necessary for the head-neck junction to reach the resection line. After positioning the wire on the femoral head surface along the resection line from the 9- to 12-o'clock area of the femoral head, we measured the target alpha angle on radiographs at 0°, 15°, 30°, 45°, and 60° of hip flexion using the frog-leg 45/45/30 view (45° of flexion, 45° of abduction, and 30° of external rotation) and Dunn 45 view (45° of flexion, 20° of abduction, and neutral rotation).
  
  
  RESULTS
  The mean hip flexion angle at which the head-neck junction reached the resection line was 31° ± 4.6°. For 0°, 15°, 30°, 45°, and 60° of hip flexion, the mean target alpha angle was 75.5° ± 5.5°, 65.3° ± 5.6°, 56.3° ± 5.8°, 49.0° ± 6.6°, and 42.6° ± 5.8°, respectively, using the frog-leg 45/45/30 view and 75.0° ± 6.0°, 65.8° ± 6.2°, 57.2° ± 7.3°, 50.7° ± 6.9°, and 44.2° ± 5.8°, respectively, using the Dunn 45 view. There were no significant differences between the 2 radiographic techniques (P = .82, P = .84, P = .76, P = .57, and P = .52, respectively).
  
  
  CONCLUSIONS
  A description of the degree of hip flexion during cam resection can affect the final alpha angle when using the labrum as a reference for resection.
  
  
  CONCLUSIONS
  The described index allows systematic navigation of cam lesions during arthroscopy for femoroacetabular impingement patients using the hip flexion angle.
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Yamasaki
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan. Electronic address: hussy@med.osaka-cu.ac.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hashimoto
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Shozaburo
authors.initials: S
authors.lastname: Terai
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Junsei
authors.initials: J
authors.lastname: Takigami
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001182:Arthroscopy / Q000379:methods*; D002358:Cartilage, Articular / Q000473:pathology; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D005270:Femur Head / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D056888:Patient Positioning; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology; D011859:Radiography; D016059:Range of Motion, Articular; D012016:Reference Values