title: Kinematic analysis of the indirect femoral insertion of the anterior cruciate ligament: implications for anatomic femoral tunnel placement.
abstract: OBJECTIVE
  To determine the effect of debriding the indirect insertion component of the femoral anterior cruciate ligament (ACL) attachment on tibiofemoral kinematics when compared with the intact knee.
  
  
  METHODS
  Knee kinematics were measured in 9 cadaveric knees with the ACL intact, after indirect insertion debridement, and after ACL transection. Three loading conditions were used: (1) a 134-N anterior tibial load, (2) a combined 10-Nm valgus and 5-Nm internal tibial torque, and (3) a simulated robotic pivot shift. Anterior tibial translation (ATT) was recorded in response to anterior and combined loads at 0°, 15°, 30°, 45°, 60°, and 90° of flexion. Posterior tibial translation and external tibial rotation were recorded during the simulated pivot shift.
  
  
  RESULTS
  With an anterior load, indirect insertion debridement increased ATT by 0.37 ± 0.24 mm at 0° (P = .002) and by 0.16 ± 0.19 mm at 15° (P = .033; increases <1 mm in all specimens). ACL transection increased ATT in response to an anterior load (P = .0001) with maximum effect at 15° compared with the intact and debrided states (11.26 ± 1.15 mm and 11.04 ± 1.08 mm, respectively). With a combined load, indirect insertion debridement increased ATT by 0.17 ± 0.11 mm at 0° (P = .001; increases <0.3 mm in all specimens) with no effect at other angles. ACL transection increased ATT in response to a combined load (P = .001) with maximum effect at 15° (4.45 ± 0.85 mm v ACL intact and 4.44 ± 0.84 mm v debrided indirect insertion). In the ACL intact condition, the pivot shift produced 1.29 ± 1.34 mm of posterior tibial translation and 1.54 ± 1.61° of external tibial rotation, as compared with 1.28 ± 1.34 mm and 1.54 ± 1.47°, respectively, after debridement (P = .68 and P = .99, respectively) and 12.79 ± 3.22 mm and 17.60 ± 4.30°, respectively, after ACL transection (P = .0001).
  
  
  CONCLUSIONS
  The indirect femoral ACL insertion contributes minimally to restraint of tibial translation and rotation.
  
  
  CONCLUSIONS
  Femoral tunnel positioning for anatomic ACL reconstruction should aim to recreate the biomechanically significant direct insertion.
authors.affiliation: Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, U.S.A.. Electronic address: neil.pathare@gmail.com.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Pathare
authors.affiliation: Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, U.S.A.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Nicholas
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, and Orthopaedic Research Center, Cleveland Clinic, Cleveland, Ohio, U.S.A.
authors.forename: Robb
authors.initials: R
authors.lastname: Colbrunn
authors.affiliation: Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York, New York, U.S.A.
authors.forename: Malachy P
authors.initials: MP
authors.lastname: McHugh
mesh_terms: D016118:Anterior Cruciate Ligament / Q000502:physiology* / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D003646:Debridement / Q000523:psychology*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D016059:Range of Motion, Articular; D012371:Robotics; D012399:Rotation; D013977:Tibia; D019415:Torque