title: Femoral and tibial graft tunnel parameters after transtibial, anteromedial portal, and outside-in single-bundle anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Anatomic graft tunnel placement is recommended in anterior cruciate ligament (ACL) reconstruction to restore knee joint stability and function. Transtibial (TT), anteromedial portal (AMP), and outside-in (OI) retrograde drilling surgical techniques have been described for tibial and femoral bone tunnel preparation.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the bone tunnel parameters and compare the ability of 3 different surgical techniques to achieve placement of the ACL femoral and tibial bone tunnels at the center of the native ACL femoral and tibial attachment sites. The hypothesis was that tunnel placement using an AMP or OI technique would result in optimized tunnel parameters and more closely reconstruct the center of the native ACL femoral attachment site.
  
  
  METHODS
  Cohort study; Level of evidence, 3.
  
  
  METHODS
  The study population consisted of 100 patients undergoing anatomic single-bundle ACL reconstruction using multiple-stranded hamstring tendon grafts. In group 1 (n = 36), the femoral tunnel was drilled using a TT surgical technique; in group 2 (n = 32), the femoral tunnel was drilled through an AMP; and in group 3 (n = 32), the femoral tunnel was created by use of an OI technique with retrograde drilling. Computed tomography (CT) scans were obtained postoperatively, and characteristics of femoral and tibial tunnel apertures were correlated to femoral and tibial measurement grid systems. The position of the resulting tibial and femoral bone tunnels for each group was compared with the center of the native ACL attachment sites.
  
  
  RESULTS
  There were statistically significant differences (P < .05) for the ACL femoral tunnel between the 3 groups with respect to intercondylar height, total tunnel length, graft fixation length, tunnel axis, and tunnel entry angle. Statistically significant differences (P < .05) were found for the ACL tibial tunnel with respect to anteroposterior tunnel position and sagittal tunnel axis between the TT and both the OI and AMP techniques. The OI surgical technique produced more oblique and anatomically correct femoral tunnel apertures and longer femoral tunnel lengths compared with the AMP technique. Both AMP and OI techniques resulted in a more precise replication of intercondylar tunnel depth and height. There was no statistically significant difference for graft fixation length between the AMP and OI techniques.
  
  
  CONCLUSIONS
  The AMP and OI surgical techniques were superior in positioning the ACL femoral tunnel at the center of the native ACL attachment site compared with the TT technique. An acceptable graft fixation length was obtained for all 3 surgical techniques.
authors.affiliation: Department for Trauma Surgery and Sports Traumatology, Academic Hospital Feldkirch, Feldkirch, Austria michael.osti@lkhf.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Osti
authors.affiliation: Department for Diagnostic and Interventional Radiology, Academic Hospital Feldkirch, Feldkirch, Austria.
authors.forename: Alessa
authors.initials: A
authors.lastname: Krawinkel
authors.affiliation: Department for Trauma Surgery and Sports Traumatology, Academic Hospital Feldkirch, Feldkirch, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Ostermann
authors.affiliation: Department for Trauma Surgery and Sports Traumatology, Paracelsus Medical University Salzburg, Salzburg, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoffelner
authors.affiliation: Department for Trauma Surgery and Sports Traumatology, Academic Hospital Feldkirch, Feldkirch, Austria.
authors.forename: Karl Peter
authors.initials: KP
authors.lastname: Benedetto
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001182:Arthroscopy / Q000379:methods; D015331:Cohort Studies; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013525:Surgical Instruments; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: ACL reconstruction, transtibial technique; anatomy; anteromedial portal technique; computed tomography; outside-in technique