title: Dynamic quantification of tibio-femoral rotation in postero-lateral bundle insufficiency of the anterior cruciate ligament: a cadaver study.
abstract: OBJECTIVE
  Anterior cruciate ligament (ACL) injury represents one of the most common diagnoses in orthopaedic sports medicine. In the past, anatomic knowledge about the different bundles within the cruciate ligaments triggered new treatment concepts, such as double-bundle ACL reconstruction. Recently, besides complete tearing, partial ACL ruptures and bundle augmentation became a focus. However, only little is known regarding rotational stability of the knee with an isolated torn postero-lateral (PL) bundle. Therefore, the aim of the present study was the torsiometric analysis of tibio-femoral restraint patterns of the PL-insufficient knee joint.
  
  
  METHODS
  Fresh human whole body cadavers were enrolled. After diagnostic arthroscopy to ensure the structural integrity of the cruciate ligaments, knee joints underwent torsiometry at 0°, 30°, and 90° degree flexion. Then stepwise the PL bundle and the anteromedial (AM) bundle were arthroscopically resected, while torsiometry of the PL- as well as of the ACL-deficient knee joints was repeated. An area under the curve (AUC) was calculated. All statistical analyses were conducted using a p-value of 0.05 as level of significance.
  
  
  RESULTS
  The comparison of charged and equilibrated curves during internal rotation revealed significant results at low flexion (30° flexion) angles between the ACL intact versus PL absent conditions (p = 0.04). In addition, charged and equilibrated curves during external rotation at 90° flexion, thus high angles, resulted in a significant difference when comparing the ACL-intact with the PL-deficient condition (p = 0.01).
  
  
  CONCLUSIONS
  In the present cadaver study using the Torsiometer tool we found a distinct destabilization of the rotational restraints in full knee extension only after total ACL resection. In contrast, no significant findings resulted after an isolated dissection of the PL bundle during internal deflection. Nevertheless, a significant loss of stability was found during unstressed external deflection after isolated PL bundle dissection. Therefore patients, undergoing PL augmentation might benefit regarding rotational instability patterns.
authors.affiliation: Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universitaet Muenchen, Ismaningerstrasse 22, 81675, Munich, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Lorenz
authors.forename: Philipp
authors.initials: P
authors.lastname: Ahrens
authors.forename: Sonja
authors.initials: S
authors.lastname: Kirchhoff
authors.forename: Petra
authors.initials: P
authors.lastname: Wolf
authors.forename: Stefan
authors.initials: S
authors.lastname: Hinterwimmer
authors.forename: Andreas
authors.initials: A
authors.lastname: Obermeier
authors.forename: Marc
authors.initials: M
authors.lastname: Beirer
authors.forename: Chlodwig
authors.initials: C
authors.lastname: Kirchhoff
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D002102:Cadaver; D005260:Female; D005269:Femur / Q000502:physiology; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D012421:Rupture; D013977:Tibia / Q000502:physiology; D054159:Torsion, Mechanical