title: Torsional force applied to the tibia of living lambs in an attempt to change the bone rotational axis.
abstract: OBJECTIVE
  To evaluate the effects of torsional force on the rotational axis of living lamb tibias.
  
  
  METHODS
  An external fixator device was designed to apply rotation to the tibias of lambs. Once a week, the bone distal extremity was rotated 2º. After achieving ~20º of internal rotation, the turning was discontinued and the device was maintained in situ for one month and euthanasia occurred in group A (n=10) after this. In group B (n=9) euthanasia occurred three months after removing the device. Computed tomography scans evaluated the rotational angle; dual-energy X-ray absorptiometry assessed the bone mineral density, and conventional and polarized light microscopy studied the bone microstructure.
  
  
  RESULTS
  In group A, the mean angle of the external rotation in the control tibias was 24º and 8º in the twisted tibias (p<0.0001); in group B, the angle was 23º (control) and 7º (twisted, p<0.0001), with no differences between groups A and B (p=0.9567). The BMD increased in the twisted tibias in group A (p<0.0001) and in group B (p=0.0023), with no between-group differences (p>0.05). Microscopically, the twisted tibias showed asymmetrical subperiosteal bone deposition on the lateral cortex surface.
  
  
  CONCLUSIONS
  Gradual torsion applied to the immature tibia significantly modified its rotational axis.
authors.affiliation: University of Sao Paulo, School of Medicine of Ribeirao Preto, Department of Biomechanics, Medicine and Rehabilitation of the Locomotor System, Brazil, PhD, Full Professor, Department of Biomechanics, Medicine and Rehabilitation of the Locomotor System, School of Medicine of Ribeirao Preto, University of Sao Paulo (USP), Brazil. Design, intellectual and scientific content of the study, interpretation of data, manuscript writing, critical revision.
authors.forename: José Batista
authors.initials: JB
authors.lastname: Volpon
authors.affiliation: USP, School of Medicine of Ribeirao Preto, Brazil, Fellow PhD degree, Postgraduate Program in Health Sciences Applied to the Locomotor System, School of Medicine of Ribeirao Preto, USP, Brazil. Animal care, technical procedures.
authors.forename: Maurício José
authors.initials: MJ
authors.lastname: Falcai
authors.affiliation: USP, School of Medicine of Ribeirao Preto, Brazil, Master, Engineer, Laboratory of Bioengineering, School of Medicine of Ribeirao Preto, USP, Brazil. Torsion device design and mechanical testing performance.
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Moro
authors.affiliation: USP, School of Medicine of Ribeirao Preto, Brazil, Fellow PhD degree, Postgraduate Program in Health Sciences Applied to the Locomotor System, School of Medicine of Ribeirao Preto, USP, Brazil. Animal care, technical procedures, critical revision.
authors.forename: Daniel Mendes
authors.initials: DM
authors.lastname: Leal
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D004867:Equipment Design; D016268:Internal Fixators; D008297:Male; D008488:Medical Illustration; D008859:Microscopy, Polarization; D012016:Reference Values; D015203:Reproducibility of Results; D012399:Rotation; D012756:Sheep; D013977:Tibia / Q000502:physiology*; D054159:Torsion, Mechanical