title: Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study.
abstract: OBJECTIVE
  To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model.
  
  
  METHODS
  Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension.
  
  
  RESULTS
  Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion.
  
  
  CONCLUSIONS
  The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.
authors.affiliation: Musculoskeletal Imaging and Biomechanics Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, PA 15213, USA. kaufmannra@upmc.edu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kaufmann
authors.forename: H James
authors.initials: HJ
authors.lastname: Pfaeffle
authors.forename: Brad D
authors.initials: BD
authors.lastname: Blankenhorn
authors.forename: Kathryne
authors.initials: K
authors.lastname: Stabile
authors.forename: Doug
authors.initials: D
authors.lastname: Robertson
authors.forename: Robert
authors.initials: R
authors.lastname: Goitz
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002102:Cadaver; D050824:Carpal Joints / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014955:Wrist Joint / Q000000981:diagnostic imaging / Q000502:physiology*