title: Evaluation of the Length and Isometric Pattern of the Anterolateral Ligament With Serial Computer Tomography.
abstract: BACKGROUND
  Recent anatomical studies have identified the anterolateral ligament (ALL). Injury to this structure may lead to the presence of residual pivot shift in some reconstructions of the anterior cruciate ligament. The behavior of the length of this structure and its tension during range of motion has not been established and is essential when planning reconstruction.
  
  
  OBJECTIVE
  To establish differences in the ALL length during range of knee motion.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Ten unpaired cadavers were dissected. The attachments of the ALL were isolated. Its origin and insertion were marked with a 2 mm-diameter metallic sphere. Computed tomography scans were performed on the dissected parts under extension and 30°, 60°, and 90° of flexion; measurements of the distance between the 2 markers were taken at all mentioned degrees of flexion. The distances between the points were compared.
  
  
  RESULTS
  The mean ALL length increased with knee flexion. Its mean length at full extension and at 30°, 60°, and 90° of flexion was 37.9 ± 5.3, 39.3 ± 5.4, 40.9 ± 5.4, and 44.1 ± 6.4 mm, respectively. The mean increase in length from 0° to 30° was 3.99% ± 4.7%, from 30° to 60° was 4.20% ± 3.2%, and from 60° to 90° was 7.45% ± 4.8%. From full extension to 90° of flexion, the ligament length increased on average 16.7% ± 12.1%. From 60° to 90° of flexion, there was a significantly higher increase in the mean distance between the points compared with the flexion from 0° to 30° and from 30° to 60°.
  
  
  CONCLUSIONS
  The ALL shows no isometric behavior during the range of motion of the knee. The ALL increases in length from full extension to 90° of flexion by 16.7%, on average. The increase in length was greater from 60° to 90° than from 0° to 30° and from 30° to 60°. The increase in length at higher degrees of flexion suggests greater tension with increasing flexion.
  
  
  CONCLUSIONS
  Knowledge of ALL behavior during the range of motion of the knee will allow for fixation (during its reconstruction) to be performed with a higher or lower tension, depending on the chosen degree of flexion.
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Camilo Partezani
authors.initials: CP
authors.lastname: Helito
authors.affiliation: Department of Radiology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Paulo Victor Partezani
authors.initials: PV
authors.lastname: Helito
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Marcelo Batista
authors.initials: MB
authors.lastname: Bonadio
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Roberto Freire
authors.initials: RF
authors.lastname: da Mota E Albuquerque
authors.affiliation: Department of Radiology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Bordalo-Rodrigues
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Jose Ricardo
authors.initials: JR
authors.lastname: Pecora
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Marco Kawamura
authors.initials: MK
authors.lastname: Demange
keywords: anatomy; anterolateral ligament; rotatory instability; tomography