title: Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study.
abstract: Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positions on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo.
  
  
  
  Eighty-one volunteers were computed tomography-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each "disc" set as the reference surface and separated into 5 anatomical zones: 4 peripheral and 1 central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions and were compared against each other with analysis of variance, with significance set at P < .05.
  
  
  
  Mean neutral disc height was 7.32 mm (1.59 mm). With 50° rotation, a small but significant increase to 7.44 mm (1.52 mm) (P < .0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (P < .0001), whereas the left, anterior, and central decreased.
  
  
  
  This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown.
authors.affiliation: Assistant Professor, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL.
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Espinoza Orías
authors.affiliation: Research Assistant, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Mammoser
authors.affiliation: Professor, Research Graduate Education and Research Program & Director, Partnerships and Research Commercialization, Canadian Memorial Chiropractic College, North York, ON, Canada.
authors.forename: John J
authors.initials: JJ
authors.lastname: Triano
authors.affiliation: The Morton International Professor, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL; Director of Spine Surgery and Spine Fellowship, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL.
authors.forename: Howard S
authors.initials: HS
authors.lastname: An
authors.affiliation: The Ronald L. DeWald, M.D. Professor, Chairman Emeritus, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL.
authors.forename: Gunnar B J
authors.initials: GB
authors.lastname: Andersson
authors.affiliation: Professor, Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL. Electronic address: Nozomu_Inoue@rush.edu.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Inoue
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D059350:Chronic Pain / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000502:physiology / Q000503:physiopathology; D017116:Low Back Pain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology / Q000503:physiopathology; D020393:Manipulation, Spinal; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D012399:Rotation; D014057:Tomography, X-Ray Computed; D054159:Torsion, Mechanical; D055815:Young Adult
keywords: Computed Tomography; Imaging; Intervertebral Disc; Mechanical; Spinal Manipulation; Three-Dimensional; Torsion