title: Capitate-based kinematics of the midcarpal joint during wrist radioulnar deviation: an in vivo three-dimensional motion analysis.
abstract: OBJECTIVE
  The purpose of this study was to obtain qualitative and quantitative information regarding in vivo 3-dimensional (3D) kinematics of the midcarpal joint during wrist radioulnar deviation (RUD).
  
  
  METHODS
  We studied the in vivo kinematics of the midcarpal joint during wrist RUD in the right wrists of 10 volunteers by using a technology without radioactive exposure. The magnetic resonance images were acquired during RUD. The capitate was registered with the scaphoid, the lunate, and the triquetrum by using a volume registration technique. Animations of the relative motions of the midcarpal joint were created and accurate estimates of the relative orientations of the bones and axes of rotation (AORs) of each motion were obtained.
  
  
  RESULTS
  The scaphoid, lunate, and triquetrum motions relative to the capitate during RUD were found to be similar, describing a rotational motion around the axis obliquely penetrating the head of the capitate in almost a radial extension/ulnoflexion plane of motion of the wrist. The AORs of the scaphoid, the lunate, and the triquetrum were located closely in space. In the axial plane the AORs of the scaphoid, lunate, and triquetrum formed a radially and palmarly opening angle of 43 degrees +/- 7 degrees, 41 degrees +/- 11 degrees, and 42 degrees +/- 14 degrees with the wrist flexion/extension axis, respectively.
  
  
  CONCLUSIONS
  This study reports the in vivo 3D measurements of midcarpal motion relative to the capitate. Isolated midcarpal motion during RUD could be approximated to be a rotation in a plane of a radiodorsal/ulnopalmar rotation of the wrist, which may coincide with a motion plane of one of the most essential human wrist motions, known as the dart-throwing motion.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Moritomo
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Murase
authors.forename: Akira
authors.initials: A
authors.lastname: Goto
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Oka
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002348:Carpal Bones / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D011884:Radius / Q000502:physiology; D014457:Ulna / Q000502:physiology; D014955:Wrist Joint / Q000502:physiology*