title: Length change patterns in the lateral extra-articular structures of the knee and related reconstructions.
abstract: BACKGROUND
  Lateral extra-articular soft tissue reconstructions in the knee may be used as a combined procedure in revision anterior cruciate ligament surgery as well as in primary treatment for patients who demonstrate excessive anterolateral rotatory instability. Only a few studies examining length change patterns and isometry in lateral extra-articular reconstructions have been published.
  
  
  OBJECTIVE
  To determine a recommended femoral insertion area and graft path for lateral extra-articular reconstructions by measuring length change patterns through a range of knee flexion angles of several combinations of tibial and femoral insertion points on the lateral side of the knee.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Eight fresh-frozen cadaveric knees were freed of skin and subcutaneous fat. The knee was then mounted in a kinematics rig that loaded the quadriceps muscles and simulated open-chain knee flexion. The length changes of several combinations of tibiofemoral points were measured at knee flexion angles between 0° and 90° by use of linear variable displacement transducers. The changes in length relative to the 0° measurement were recorded.
  
  
  RESULTS
  The anterior fiber region of the iliotibial tract displayed a significantly different (P < .001) length change pattern compared with the posterior fiber region. The reconstructions that had a femoral insertion site located proximal to the lateral epicondyle and with the grafts passed deep to the lateral collateral ligament displayed similar length change patterns to each other, with small length increases during knee extension. These reconstructions also showed a significantly lower total strain range compared with the reconstruction located anterior to the epicondyle (P < .001).
  
  
  CONCLUSIONS
  These findings show that the selection of graft attachment points and graft course affects length change pattern during knee flexion. A graft attached proximal to the lateral femoral epicondyle and running deep to the lateral collateral ligament will provide desirable graft behavior, such that it will not suffer excessive tightening or slackening during knee motion.
  
  
  CONCLUSIONS
  These results provide a surgical rationale for lateral extra-articular soft tissue reconstruction in terms of femoral graft fixation site and graft route.
authors.affiliation: The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, UK Department of Trauma Surgery, Landeskrankenhaus Steyr, Steyr, Austria.
authors.forename: Cristoph
authors.initials: C
authors.lastname: Kittl
authors.affiliation: The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, UK.
authors.forename: Camilla
authors.initials: C
authors.lastname: Halewood
authors.affiliation: The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, UK.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Stephen
authors.affiliation: The MSk Lab, Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Chinmay M
authors.initials: CM
authors.lastname: Gupte
authors.affiliation: Sporthopaedicum Berlin, Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Weiler
authors.affiliation: Fortius Clinic, London, UK.
authors.forename: Andy
authors.initials: A
authors.lastname: Williams
authors.affiliation: The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, UK The MSk Lab, Department of Surgery and Cancer, Imperial College London, London, UK a.amis@imperial.ac.uk.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D052097:Quadriceps Muscle / Q000601:surgery*; D012086:Reoperation; D013977:Tibia / Q000601:surgery; D019737:Transplants
keywords: anterolateral ligament; anterolateral rotatory instability; isometry; knee, anterior cruciate ligament; lateral extra-articular soft tissue reconstruction; length change pattern