title: Varus alignment leads to increased forces in the anterior cruciate ligament.
abstract: BACKGROUND
  Varus thrust of the knee is a dynamic increase of an often preexisting varus angle and it is suspected to be a major reason for failure of anterior cruciate ligament reconstructions. However, it is not known if a direct relationship exists between varus thrust and forces in the anterior cruciate ligament.
  
  
  OBJECTIVE
  Forces in the anterior cruciate ligament increase with increasing varus alignment, and consequently an anterior cruciate ligament deficiency in a varus-aligned leg leads to more lateral tibiofemoral joint opening.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Six human cadaver legs were axially loaded with 3 different weightbearing lines--a neutral weightbearing line, a weightbearing line that passes through the middle of the medial tibial plateau (50% varus), and a line passing the edge of the medial tibial plateau (100% varus)--that were used to create a varus moment. The resulting lateral tibiofemoral joint opening and corresponding anterior cruciate ligament tension were measured. The tests were repeated with and without the anterior cruciate ligament in place.
  
  
  RESULTS
  In the neutral aligned legs, there was no apparent lateral joint opening, and no anterior cruciate ligament tension change was noted. The lateral joint opening increased when the weightbearing line increased from 0% to 50% to 100%. The lateral joint opening was significantly higher in 10 degrees of knee flexion compared with knee extension. In the 100% varus weightbearing line, the anterior cruciate ligament tension was significantly higher (53.9 N) compared with neutral (31 N) or the 50% weightbearing line (37.9 N). A thrust could only be observed in the 100% weightbearing line tests. In the absence of an anterior cruciate ligament, there was more lateral joint opening, although this was only significant in the 100% weightbearing line.
  
  
  CONCLUSIONS
  There is a direct relationship between varus alignment and anterior cruciate ligament tension. In the absence of an anterior cruciate ligament, the amount of lateral opening tends to increase. With increasing lateral opening, a thrust can sometimes be experimentally observed.
  
  
  CONCLUSIONS
  A varus alignment in an anterior cruciate ligament-deficient knee does not necessarily lead to a varus thrust and therefore does not always need operative varus alignment correction. However, in an unstable anterior cruciate ligament-deficient knee with a varus thrust, it might be safer to perform a high valgus tibial osteotomy to minimize the risk of an anterior cruciate ligament reconstruction failure.
authors.affiliation: Department of Orthopaedics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Gerrit Jan
authors.initials: GJ
authors.lastname: van de Pol
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 / Q000503:physiopathology*; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D013314:Stress, Mechanical; D016474:Weight-Bearing