title: In vivo three-dimensional motion analysis of chronic radial head dislocations.
abstract: BACKGROUND
  Forearm kinematics and interosseous membrane function in chronic radial head dislocations sustained in childhood are unknown. Several procedures have been performed to reduce the radial head on the basis of static preoperative assessment in only one forearm position, but clinical results are not always favorable.
  
  
  OBJECTIVE
  We investigated the in vivo three-dimensional (3D) kinematics and length changes of interosseous membrane ligaments during forearm rotation in chronic radial head dislocations using 3D CT registration techniques.
  
  
  METHODS
  We examined 10 patients with chronic radial head dislocations (seven Type 1 and three Type 4 Monteggia lesions). To quantify kinematics, the axis of rotation (AOR) and radial head motion were investigated using computer bone models constructed from CT data placing the forearm in three positions. We also created six interosseous membrane ligaments and calculated their 3D lengths during forearm rotation.
  
  
  RESULTS
  In Type 1 lesions, the AOR was located 2.4 mm from the center of the radial head (COR). The COR translated 2.8 mm sagittally and 3.4 mm coronally. Three interosseous membrane ligaments showed little change in length. In Type 4 lesions, the AOR was located 6.2 mm from the COR. The COR translated 10.2 mm sagittally and 4.7 mm coronally. No ligament showed an isometric pattern.
  
  
  CONCLUSIONS
  In Type 1 lesions, the radial head showed relatively stable motion in the dislocated position and the isometricity of the interosseous membrane remained, which supports the concept of ulnar osteotomy. Conversely, the radial head was unstable and the normal interosseous membrane ligament tautness pattern was disrupted in Type 4 lesions.
  
  
  METHODS
  Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan. miyake-osk@umin.ac.jp
authors.forename: Junichi
authors.initials: J
authors.lastname: Miyake
authors.forename: Hisao
authors.initials: H
authors.lastname: Moritomo
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kataoka
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Murase
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002908:Chronic Disease; D004551:Elbow Joint / Q000503:physiopathology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D004204:Joint Dislocations / Q000503:physiopathology*; D008297:Male; D009068:Movement; D014057:Tomography, X-Ray Computed; D055815:Young Adult; D000092464:Elbow Injuries