title: Radiological evaluation for conflict of the femoral tunnel entrance area prior to anterior cruciate ligament revision surgery.
abstract: OBJECTIVE
  Anterior cruciate ligament (ACL) revision surgery is a demanding procedure and requires meticulous pre-operative clinical and radiological assessment. In clinical practice the position of the femoral tunnel is identified mainly using plain radiographs (XR). Two-dimensional computed tomography (2D-CT) and magnetic resonance imaging (MRI) are not yet routine imaging methods and are only performed in specific clinical indications or in the scientific setting. Several measurement methods describe the femoral tunnel after ACL reconstruction and indicate 'ideal or wrong' placement to the surgeon. The aim of this study is to provide a reliable measurement method to predict potential conflict between the pre-existing and the planned femoral tunnel entrance area (FTEA).
  
  
  METHODS
  Ten patients with primary ACL reconstruction served as a reference group to describe our desired FTEA. Their femoral tunnel positioning was measured on XR and 2D-CT according to published measurement methods. These results were compared to the FTEA measured with a new technique on 3-dimensionally reconstructed CT-images (3D-CT) based on intra-operative landmarks. Twenty patients requiring ACL revision surgery underwent identical radiological examination. The mean values of the reference group were compared to each measurement of the patients requiring revision surgery.
  
  
  RESULTS
  3D-CT measurements found potential conflicts in nine out of 20 patients, which all proved to be true during arthroscopic revision surgery. Only one of these patients was identified in all XR and 2D-CT measurements. In 12 out of all 30 patients some measurements on XR or 2D-CT could not be recorded.
  
  
  CONCLUSIONS
  3D-CT reconstruction shows the most accuracy in depicting conflict of the pre-existing and desired femoral tunnel prior to ACL revision surgery. The desired FTEA must be defined for each surgeon and his individual technique. In contrast, precision of conventional measurement techniques on XR and 2D-CT is low and does not qualify for this purpose.
authors.affiliation: Sportclinic Villa Linde, Swiss Olympic Medical Center Magglingen-Biel, Blumenrain 87, CH-2503, Biel, Switzerland, ph.tscholl@sunrise.ch.
authors.forename: Philippe M
authors.initials: PM
authors.lastname: Tscholl
authors.forename: Roland M
authors.initials: RM
authors.lastname: Biedert
authors.forename: Imre
authors.initials: I
authors.lastname: Gal
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001182:Arthroscopy / Q000379:methods; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011859:Radiography / Q000379:methods; D012086:Reoperation; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult