title: Biomechanical analysis of knee laxity with isolated anteromedial or posterolateral bundle-deficient anterior cruciate ligament.
abstract: OBJECTIVE
  The purpose of this study was to clarify the changes in the kinematics of the knee that result from isolated deficiency of the anteromedial (AM) or posterolateral (PL) bundle.
  
  
  METHODS
  Fourteen cadaveric knees were mounted in a 6-df rig and tested using the following 5 loading conditions: 90-N anterior and posterior tibial loads, 5-Nm internal and external tibial torques, and a simulated pivot-shift test. Tibiofemoral kinematics during flexion-extension was recorded with an optical tracking system for (1) intact knees, (2) knees in which the isolated AM bundle was cut, (3) knees in which the isolated PL bundle was cut, and (4) anterior cruciate ligament (ACL)-deficient knees. The distances between the femoral and tibial attachments of the AM and PL bundles of the ACL were also calculated.
  
  
  RESULTS
  Anterior translation laxity under an anterior tibial load, rotational laxity under an internal tibial torque, and anterior translation laxity under pivot-shift loading were significantly different between the knees with AM and PL bundle deficiencies (P < .024), but the changes were small: less than 3 mm or 1.5°. The AM bundle distance increased significantly more after an AM bundle tear (P = .004) than after a PL bundle tear in flexion. Cutting the PL bundle did not have a significant effect on the lengths between the bundle attachments.
  
  
  CONCLUSIONS
  An isolated AM or PL bundle tear caused a small increase in laxity (<3 mm or <1.5°).
  
  
  CONCLUSIONS
  If there is a clinically identifiable increase in laxity, then--in addition to the isolated tear of the AM or PL bundle--there must also be a tear of the other bundle of the ACL, or at least a partial tear.
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London, England; Department of Sports Medicine and Joint Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan. Electronic address: eijik@med.hokudai.ac.jp.
authors.forename: Eiji
authors.initials: E
authors.lastname: Kondo
authors.affiliation: Department of Musculoskeletal Surgery, Imperial College London, London, England; Orthopaedic Surgery Department, University of Malaya Medical Centre, Kuala Lumpur, Malaysia.
authors.forename: Azhar M
authors.initials: AM
authors.lastname: Merican
authors.affiliation: Department of Sports Medicine and Joint Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yasuda
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London, England; Department of Musculoskeletal Surgery, Imperial College London, London, England.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amis
mesh_terms: D000328:Adult; D000368:Aged; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005269:Femur / Q000503:physiopathology; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008875:Middle Aged; D016059:Range of Motion, Articular; D013977:Tibia / Q000503:physiopathology; D019415:Torque