title: Anatomical anterior cruciate ligament reconstruction: transtibial versus outside-in technique: SIGASCOT Best Paper Award Finalist 2014.
abstract: OBJECTIVE
  the aim of this study was to compare clinical results and location of the femoral tunnel with transtibial (TT) and outside-in (OI) techniques in anterior cruciate ligament (ACL) reconstruction using in vivo 3D CT analysis.
  
  
  METHODS
  we prospectively followed up 40 ACL reconstructions in which femoral tunnel placement was performed using two different techniques: TT [20] and OI [20]. Clinical evaluation was based on IKDC and KOOS scores and radiographic analysis with specific 3D CT scans. Tunnel coordinates were calculated using the Bernard-Hertel quadrant method to define the insertion point of the ACL.
  
  
  RESULTS
  excellent clinical results were achieved in both groups, which showed comparable IKDC and KOOS scores. Two failures were recorded, both in the TT group. In the high-to-low direction, the position of the femoral tunnel, as measured using the quadrant method, was too high in the TT group, compared to what was observed in the OI group: 10.5 ± 6.9% (0-29%) and 30.2 ± 5.4% (19-42%), (p=0.043).
  
  
  CONCLUSIONS
  we found that with the TT technique, compared with the OI technique, the femoral tunnel was located higher in the high-to-low direction and was in a slightly shallower position in the deep-to-shallow direction. Using the OI technique the femoral tunnel was in a position closer to the anatomical ACL footprint than with the TT technique. A femoral tunnel position far from the anatomical footprint of the native ACL would result in a higher failure rate.
  
  
  METHODS
  level II, prospective comparative study.
authors.affiliation: Orthopaedic Clinic, University of Florence, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Matassi
authors.affiliation: Orthopaedic Clinic, University of Florence, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Sirleo
authors.affiliation: Orthopaedic Clinic, University of Florence, Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Carulli
authors.affiliation: Orthopaedic Clinic, University of Florence, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Innocenti
keywords: ACL reconstruction; anterior cruciate ligament; knee; outside-in technique; quadrant method; transtibial technique; tunnel placement