title: The role of fibers in the femoral attachment of the anterior cruciate ligament in resisting tibial displacement.
abstract: OBJECTIVE
  The purpose was to clarify the load-bearing functions of the fibers of the femoral anterior cruciate ligament (ACL) attachment in resisting tibial anterior drawer and rotation.
  
  
  METHODS
  A sequential cutting study was performed on 8 fresh-frozen human knees. The femoral attachment of the ACL was divided into a central area that had dense fibers inserting directly into the femur and anterior and posterior fan-like extension areas. The ACL fibers were cut sequentially from the bone: the posterior fan-like area in 2 stages, the central dense area in 4 stages, and then the anterior fan-like area in 2 stages. Each knee was mounted in a robotic joint testing system that applied tibial anteroposterior 6-mm translations and 10° or 15° of internal rotation at 0° to 90° of flexion. The reduction of restraining force or moment was measured after each cut.
  
  
  RESULTS
  The central area resisted 82% to 90% of the anterior drawer force; the anterior fan-like area, 2% to 3%; and the posterior fan-like area, 11% to 15%. Among the 4 central areas, most load was carried close to the roof of the intercondylar notch: the anteromedial bundle resisted 66% to 84% of the force and the posterolateral bundle resisted 16% to 9% from 0° to 90° of flexion. There was no clear pattern for tibial internal rotation, with the load shared among the posterodistal and central areas near extension and mostly the central areas in flexion.
  
  
  CONCLUSIONS
  Under the experimental conditions described, 66% to 84% of the resistance to tibial anterior drawer arose from the ACL fibers at the central-proximal area of the femoral attachment, corresponding to the anteromedial bundle; the fan-like extension fibers contributed very little. This work did not support moving a single-bundle ACL graft to the side wall of the notch or attempting to cover the whole attachment area if the intention was to mimic how the natural ACL resists tibial displacements.
  
  
  CONCLUSIONS
  There is ongoing debate about how best to reconstruct the ACL to restore normal knee function, including where is the best place for ACL graft tunnels. This study found that the most important area on the femur, in terms of resisting displacement of the tibia, was in the central-anterior part of the femoral ACL attachment, near the roof of the intercondylar notch. The testing protocol did not lead to data that would support using a large ACL graft tunnel that attempts to cover the whole natural femoral attachment area.
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, Hokkaido, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kawaguchi
authors.affiliation: Department of Sports Medicine and Joint Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Kondo
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London, England.
authors.forename: Ryo
authors.initials: R
authors.lastname: Takeda
authors.affiliation: Unit of Clinical Anatomy, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Akita
authors.affiliation: Department of Sports Medicine and Joint Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yasuda
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London, England; Musculoskeletal Surgery Group, Imperial College London School of Medicine, Charing Cross Hospital, London, England. Electronic address: a.amis@imperial.ac.uk.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amis
mesh_terms: D016118:Anterior Cruciate Ligament / Q000502:physiology* / Q000601:surgery; D002102:Cadaver; D005269:Femur / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia; D016474:Weight-Bearing / Q000502:physiology*