title: Technical variables of ACL surgical reconstruction: effect on post-operative static laxity and clinical implication.
abstract: OBJECTIVE
  The hypothesis was that an alteration of different surgical variables of ACL reconstruction would produce significant changes in post-operative static laxity of knee joint.
  
  
  METHODS
  Joint laxity was acquired by a surgical navigation system for 17 patients just after graft fixation during single-bundle reconstruction with extra-articular lateral tenodesis. The analysed laxity parameters were: internal/external rotation at 30° (IE30) and 90° (IE90) of flexion, varus/valgus rotation at 0° (VV0) and 30° (VV30) of flexion and anterior/posterior displacement at 30° (AP30) and 90° (AP90) of flexion. As surgical variables, the angles between the tibial tunnel and the three planes were defined as well as the lengths of the tunnel and the relationship between native footprints and tunnels. The same analysis was performed for the femoral side. All surgical variables were combined in a multivariate analysis to assess for predictive factors between them and post-operative laxities values. To quantify the performance of each multivariate model, the correlation ratio (η2) and the corresponding P value (*P < 0.050) have been evaluated.
  
  
  RESULTS
  Multivariate analysis underlined statistically significant models for the estimation of: AP30 (η2= 0.987; P = 0.014), IE30 (η2= 0.995; P = 0.005), IE90 (η2= 0.568; P = 0.010), VV0 (η2= 0.932; P = 0.003). The parameters that greatly affected the identified models were the orientation of the tibial tunnel with respect to the three anatomical planes. The estimation of AP30, IE30 and IE90 got lower value as the orientation of the tibial tunnel with respect to transverse plane decreases. Considering the orientation to sagittal ([Formula: see text]) and coronal ([Formula: see text]) plane, we found that their reduction provoked a decrease in the estimation of AP30, IE30 and IE90 (except [Formula: see text] that did not appear in the estimation of AP30). The estimation of VV0 got an increase of [Formula: see text], and [Formula: see text] which led to a laxity reduction.
  
  
  CONCLUSIONS
  The main finding of the present in vivo study was the possibility to determine significant effects on post-operative static laxity level of different surgical variables of ACL reconstruction. In particular, the present study defined the conditions that minimize the different aspects of post-operative laxity at time-zero after surgery.
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy. stefano.zaffagnini@unibo.it.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy. stefano.zaffagnini@unibo.it.|Dipartimento Rizzoli Sicilia, Istituto Ortopedico Rizzoli, Bagheria (PA), Italy. stefano.zaffagnini@unibo.it.|Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna (BO), Italy. stefano.zaffagnini@unibo.it.
authors.forename: S
authors.identifier: http://orcid.org/0000-0002-2941-1407
authors.initials: S
authors.lastname: Zaffagnini
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.
authors.forename: C
authors.initials: C
authors.lastname: Signorelli
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy.
authors.forename: T
authors.initials: T
authors.lastname: Bonanzinga
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy.
authors.forename: T
authors.initials: T
authors.lastname: Roberti Di Sarsina
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Dipartimento Rizzoli Sicilia, Istituto Ortopedico Rizzoli, Bagheria (PA), Italy.
authors.forename: A
authors.initials: A
authors.lastname: Grassi
authors.affiliation: Orthopaedics and Traumatology, SANKO University, Gaziantep, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Budeyri
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy.|Dipartimento Rizzoli Sicilia, Istituto Ortopedico Rizzoli, Bagheria (PA), Italy.|Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna (BO), Italy.
authors.forename: G M
authors.initials: GM
authors.lastname: Marcheggiani Muccioli
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy.
authors.forename: F
authors.initials: F
authors.lastname: Raggi
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna (BO), Italy.
authors.forename: L
authors.initials: L
authors.lastname: Bragonzoni
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Ingegneria dell'Informazione, Università degli Studi di Brescia, Brescia (BS), Italy.
authors.forename: N
authors.initials: N
authors.lastname: Lopomo
authors.affiliation: Laboratorio di Biomeccanica ed Innovazione Tecnologica, Istituto Ortopedico Rizzoli, Via Di Barbiano 1/10, 40136, Bologna (BO), Italy.|Clinica Ortopedica e Traumatologica I, Istituto Ortopedico Rizzoli, Bologna (BO), Italy.|Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna (BO), Italy.
authors.forename: M
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries / Q000503:physiopathology / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000601:surgery; D008297:Male; D015999:Multivariate Analysis; D016059:Range of Motion, Articular; D012399:Rotation; D053656:Tenodesis / Q000379:methods*; D016896:Treatment Outcome
keywords: ACL reconstruction; Multivariate analysis; Navigation system; Post-operative laxity; Prediction