title: Validation study of arm positions for evaluation of global spinal balance in EOS imaging.
abstract: BACKGROUND
  The sagittal vertical axis (SVA) is important in the evaluation of spinal sagittal balance. Although the "fists-on-clavicles" (FOC) position has been widely used in radiographic examinations, it does not define shoulder flexion in detail. Meanwhile, in EOS imaging, the "hands-on-cheeks" (HOC) position is widely used but has not been well investigated. The purpose of this study was to investigate the relative usefulness of FOC and HOC in investigating SVA.
  
  
  METHODS
  Mean SVA was measured by EOS imaging using standing lateral radiographs of 34 volunteers in four different positions: relaxed (RLX), shoulder flexion at 90° with FOC (FOC90), elbows touching the trunk with FOC (FOCET), and HOC.
  
  
  RESULTS
  The mean SVA was 2.0 ± 2.1 cm in RLX; -1.4 ± 3.2 cm in FOC90; -0.5 ± 3.0 cm in FOCET; and -0.2 ± 2.9 cm in HOC. The negative shift from RLX was significantly greater in FOC90 than in FOCET (-3.4 ± 2.2 vs -2.5 ± 2.4 cm; p = 0.0182). The negative shift from RLX in HOC was almost equal to that in FOCET; the difference was 0.3 cm (-2.2 ± 2.2 vs -2.5 ± 2.4 cm; p = 0.2560).
  
  
  CONCLUSIONS
  FOC90 showed a negative SVA shift in comparison with FOCET. The difference in the mean SVA between HOC and FOCET was 0.3 cm, a clinically small difference.
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University, Fukuura 3-9, Kanazawa-ku, Yokohama City, Kanagawa Prefecture, 236-0004, Japan.
authors.forename: Kanichiro
authors.initials: K
authors.lastname: Kaneko
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University, Fukuura 3-9, Kanazawa-ku, Yokohama City, Kanagawa Prefecture, 236-0004, Japan. yaota@yokohama-cu.ac.jp.|Department of Spine and Spinal Cord, Yokohama Brain and Spine Center, Takigashira 1-2-1, Isogo-ku, Yokohama City, Kanagawa Prefecture, 235-0012, Japan. yaota@yokohama-cu.ac.jp.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Aota
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University, Fukuura 3-9, Kanazawa-ku, Yokohama City, Kanagawa Prefecture, 236-0004, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Sekiya
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University, Fukuura 3-9, Kanazawa-ku, Yokohama City, Kanagawa Prefecture, 236-0004, Japan.
authors.forename: Katsutaka
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Department of Orthopaedic Surgery, Yokohama City University, Fukuura 3-9, Kanazawa-ku, Yokohama City, Kanagawa Prefecture, 236-0004, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Saito
mesh_terms: D000328:Adult; D000368:Aged; D001132:Arm / Q000000981:diagnostic imaging* / Q000502:physiology; D002610:Cheek; D002968:Clavicle; D005240:Feasibility Studies; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods*; D004856:Postural Balance / Q000502:physiology*; D011859:Radiography; D013131:Spine / Q000000981:diagnostic imaging
keywords: Arm position; EOS imaging; Fists-on-clavicles; Hands-on-cheeks; Lateral radiographic evaluation; Sagittal vertical axis