title: The biomechanical effects of graft rotation on ACL reconstruction tunnel mismatch.
abstract: OBJECTIVE
  Bone block protrusion out of the tibial tunnel due to a relatively long graft is a common complication in anterior cruciate ligament surgical reconstruction with a patellar tendon. One possible solution is to shorten the patellar tendon graft already fixed in the femur by applying external rotation. This study aimed to evaluate the degree of shortening and biomechanical changes in porcine patellar grafts subjected to relatively higher degrees of rotation. Data obtained with rotations of 0°, 540°, 720°, and 900° were compared.
  
  
  METHODS
  Forty patellar porcine ligaments were subjected to biomechanical tests of degree of shortening, modulus of elasticity and maximum tension in the tendon before rupture. Tests were conducted using a universal mechanical testing machine and a computerized system for acquiring strength and deformation data.
  
  
  RESULTS
  Progressive shortening of the patellar ligament occurred with rotations of 0°, 540° and 720°. However, the degree of shortening showed no statistically significant difference as rotation increased from 720° to 900°. Decreased modulus of elasticity was observed compared with the graft rotation at 0° in all groups tested, but no statistically significant differences were observed among 540°, 720° and 900°. The maximum tension of the patellar tendon showed no change before rupture, regardless of the degree of rotation.
  
  
  CONCLUSIONS
  Rotating the patellar tendon is an efficient method for shortening a relatively long graft; however, more biomechanical studies are necessary to recommend this technique in clinical practice owing to the resulting decrease in graft stiffness that could compromise knee stability.
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil. ortopedistadanilo@hotmail.com.
authors.forename: Danilo Ricardo Okiishi de
authors.initials: DRO
authors.lastname: Oliveira
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Eduardo Takahashi
authors.initials: ET
authors.lastname: Garcia
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Fernando Augusto Freitas
authors.initials: FAF
authors.lastname: Fuso
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Cesar Augusto Martins
authors.initials: CAM
authors.lastname: Pereira
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Marco Martins
authors.initials: MM
authors.lastname: Lages
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Adriano Marques de
authors.initials: AM
authors.lastname: Almeida
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Tiago Lazzaretti
authors.initials: TL
authors.lastname: Fernandes
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Pedrinelli
authors.affiliation: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo (USP), R. Dr. Ovídio Pires de Campos, 333, Cerqueira César, São Paulo, 05403-010, SP, Brazil.
authors.forename: Arnaldo José
authors.initials: AJ
authors.lastname: Hernandez
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D004548:Elasticity; D005269:Femur / Q000601:surgery; D010329:Patella / Q000601:surgery; D017847:Patellar Ligament / Q000637:transplantation*; D012399:Rotation; D013552:Swine; D013718:Tensile Strength; D013977:Tibia / Q000601:surgery
keywords: ACL reconstruction; Graft rotation; Patellar tendon; Rotational stability; Tunnel mismatch