title: The effects of ACL deficiency on mediolateral translation and varus-valgus rotation.
abstract: BACKGROUND
  The anterior cruciate ligament (ACL) constrains the anterior translation and axial rotation of the tibia. However, the effect of ACL injury on the mediolateral translation and varus-valgus rotation of the tibia is unknown. Because of the oblique orientation of the ACL, we hypothesized that ACL deficiency alters mediolateral translation and varus-valgus rotation.
  
  
  METHODS
  The kinematics of 9 cadavers from full extension to 90 degrees of flexion under various loading conditions were measured before and after ACL resection using a robotic testing system.
  
  
  RESULTS
  ACL deficiency increased the medial translation of the tibia and valgus rotation, especially at 15 degrees and 30 degrees of flexion. For example, at 15 degrees, ACL deficiency increased the medial translation from 1.2 (SD 0.9) mm to 1.8 (SD 1.1) mm in response to a quadriceps load. The valgus rotation also increased from 0.8 degrees (SD 0.6) to 1.7 degrees (SD 0.8).
  
  
  CONCLUSIONS
  ACL deficiency altered both the mediolateral tibial translation and valgus-varus rotation under various loading conditions. The increased medial tibial translation could shift the contact in the medial compartment towards the medial tibial spine, a region where degeneration is observed in ACL-deficient patients. In addition to restoring anterior laxity, ACL reconstruction might need to restore the mediolateral translation of the tibia and varus-valgus rotation of the knee.
authors.affiliation: Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital/Harvard Medical School. Boston, MA, USA. gli1@partners.org
authors.forename: Guoan
authors.initials: G
authors.lastname: Li
authors.forename: Ramprasad
authors.initials: R
authors.lastname: Papannagari
authors.forename: Louis E
authors.initials: LE
authors.lastname: DeFrate
authors.forename: Jae Doo
authors.initials: JD
authors.lastname: Yoo
authors.forename: Sang Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Gill
mesh_terms: D016118:Anterior Cruciate Ligament / Q000502:physiology* / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D012371:Robotics; D012399:Rotation; D013977:Tibia / Q000502:physiology*; D016474:Weight-Bearing