title: Double-bundle ACL reconstruction: influence of femoral tunnel orientation in knee laxity analysed with a navigation system - an in-vitro biomechanical study.
abstract: BACKGROUND
  This paper reports an in-vitro study for evaluating the influence of the femoral tunnel orientation in anterior cruciate ligament (ACL) double-bundle reconstructions.
  
  
  METHODS
  This work describes the experimental protocol and results obtained for six cadaver knees using the FlashPoint optical system (Image Guided, Boulder, Colorado, USA) and a computer-assisted technique for the elaboration of anatomical and kinematic data. Each specimen was examined by the same surgeon in the following steps: (1) intact knee stability was evaluated by performing antero-posterior displacement and internal-external rotation test at 90 degrees ; (2) the ACL was resected and the knee evaluated again; (3) the ACL was reconstructed using the gracilis semi-tendinous tendon (through horizontal tunnels in femur), and the new kinematics recorded; (4) the ACL was reconstructed again with the same tendon, but with a more vertical orientation of the femoral tunnel (vertical tunnel) and kinematics was once more recorded; (5) finally the knee was dissected to digitise the anatomical structures.
  
  
  RESULTS
  Off-line computer analysis of the acquired anatomical and kinematic data showed that there was a significant statistical difference (Wilcoxon test with the Montecarlo method for small samples - p = 0.035) between horizontal tunnel (HT) and vertical tunnel (VT) reconstruction both in the antero-posterior test (median antero-posterior displacement in horizontal tunnel was 0.8 mm less than in vertical tunnel reconstruction) and in the internal-external (IE) rotation test (median internal-external rotation in horizontal tunnel reconstruction was 5 degrees less than in vertical tunnel reconstruction).
  
  
  CONCLUSIONS
  The analysis of graft behavior in reconstructed knees compared with normal and ACL-deficient knees suggests that the most horizontal tunnel performed better than the vertical tunnel, thus constraining optimally both antero-posterior and internal-external rotations. This finding suggests that femoral tunnel direction may be an important issue in ACL surgery.
authors.affiliation: Laboratorio di Biomeccanica, Istituti Ortopedici Rizzoli, Bologna, Italy. s.zaffagnini@biomec.ior.it
authors.forename: Stefano
authors.initials: S
authors.lastname: Zaffagnini
authors.forename: Danilo
authors.initials: D
authors.lastname: Bruni
authors.forename: Sandra
authors.initials: S
authors.lastname: Martelli
authors.forename: Naoaki
authors.initials: N
authors.lastname: Imakiire
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
authors.forename: Alessandro
authors.initials: A
authors.lastname: Russo
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology / Q000601:surgery*; D001696:Biomechanical Phenomena; D002102:Cadaver; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D013710:Tendons / Q000637:transplantation