title: The normal anterior cruciate ligament as a model for tensioning strategies in anterior cruciate ligament grafts.
abstract: BACKGROUND
  There is some confusion about the relationship between the tension placed on the graft and the joint position used in the fixation of anterior cruciate ligament grafts. This is because of deficiency in accurate basic science about this important interaction in the normal and reconstructed anterior cruciate ligament.
  
  
  OBJECTIVE
  If the normal femoral attachment of the anterior cruciate ligament can be preserved and the tibial insertion isolated and tested, an accurate force-flexion curve of the human anterior cruciate ligament can be mapped out and used as a standard for proper graft tensioning protocols in anterior cruciate ligament reconstruction.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  In 10 fresh-frozen human cadaveric knees, an isolated bone plug containing the tibial anterior cruciate ligament insertion was connected with a custom-made tensiometer. The knees were moved through the whole range of motion; the starting point chosen was an anterior cruciate ligament tension of 10 N, which was applied at 10 degrees of knee flexion and resulted in a baseline curve. This curve was compared with the results recorded when the starting point was below the baseline curve, similar to, or above it.
  
  
  RESULTS
  The anterior cruciate ligament showed low tension close to slackness in midflexion after starting with 10 N at 10 degrees of flexion. Starting points below the baseline curve shifted the whole curve downward; those above the baseline curve increased the force in the anterior cruciate ligament, resulting in a tight anterior cruciate ligament in midflexion.
  
  
  CONCLUSIONS
  The normal anterior cruciate ligament shows a physiological laxity in midflexion. This study gives guidelines for tensioning protocols in anterior cruciate ligament grafts to replicate the force-flexion curve characteristics of the normal anterior cruciate ligament.
authors.affiliation: Orthopaedic Department, University Hospital Groningen, The Netherlands. m.arnold@orth.azg.nl
authors.forename: Markus P
authors.initials: MP
authors.lastname: Arnold
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
authors.forename: Albert
authors.initials: A
authors.lastname: van Kampen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000502:physiology* / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D008875:Middle Aged; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures; D012421:Rupture