title: A new quasi-invariant parameter characterizing the postural alignment of young asymptomatic adults.
abstract: Our study aims to describe the postural alignment of young asymptomatic subjects from head to feet from bi-planar standing full-body X-rays, providing database to compare to aging adults. Novelty resides in the inclusion of the head and lower limbs in the erected posture's analysis.
  
  
  
  For 69 young asymptomatic subjects (18-40 years old) 3D reconstructions of the head, spine, pelvis and lower limbs segments were performed from bi-planar full-body X-rays. Usual studied spinal, pelvic and lower limbs' parameters were computed in 3D, sagittal and frontal planes of the patient. Relationships between these parameters were investigated. Inclinations of different lines were studied to characterize the erected posture.
  
  
  
  Values found for spinal curvatures, pelvic parameters and lower limbs geometrical parameters agreed with the literature: thoracic kyphosis, lumbar lordosis, pelvic incidence, pelvic tilt and sagittal vertical axis were respectively in average of 26.9° (SD 7.2°), 30.5° (SD 7.5°), 51.0° (SD 9.4°), 11.1° (SD 5.6°) and -8.9 mm (SD 21.6 mm). The angle between the vertical and the line joining the most superior point of dentiform apophyse of C2 (OD) and the center of the bi-coxofemoral axis (HA) was the less variable one (SD 1.6°).
  
  
  
  This study on 3D postural alignment reports the geometry of the spine, pelvis and lower limbs, of the young asymptomatic adult. The less variable angle is the one of the line OD-HA with the vertical, highlighting the vertical alignment of the head above the pelvis. This study provides a basis for future comparisons when investigating aging populations.
authors.affiliation: Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 bd de l'Hôpital, 75013, Paris, France. celia.amabile@ensam.eu.|Spine Service, Hospital for Special Surgery, 535 East 70th Street, Belaire 4-E, New York, NY, 10021, USA. celia.amabile@ensam.eu.
authors.forename: Celia
authors.initials: C
authors.lastname: Amabile
authors.affiliation: Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 bd de l'Hôpital, 75013, Paris, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Pillet
authors.affiliation: Spine Service, Hospital for Special Surgery, 535 East 70th Street, Belaire 4-E, New York, NY, 10021, USA.
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.affiliation: Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 bd de l'Hôpital, 75013, Paris, France.|Department of Neurosurgery and Spine Surgery, P Wertheimer Hospital, Hospices Civils de Lyon, University Claude Bernard Lyon 1, 59 Boulevard Pinel, 69003, Lyon, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Barrey
authors.affiliation: Department of Orthopaedics and Spine Surgery, University Hospital of Bordeaux, Bordeaux, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Vital
authors.affiliation: Arts et Métiers ParisTech, LBM/Institut de Biomécanique Humaine Georges Charpak, 151 bd de l'Hôpital, 75013, Paris, France.
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006257:Head / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D035002:Lower Extremity / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008297:Male; D010384:Pelvic Bones / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011187:Posture; D011859:Radiography; D012189:Retrospective Studies; D013131:Spine / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: 3D; Asymptomatic young adults; Head to feet; Skeleton’s postural alignment; Spinal alignment