title: [A new kinematics method of determing elbow rotation axis and evaluation of its feasibility].
abstract: OBJECTIVE
  To study a new positioning method of elbow external fixation rotation axis, and to evaluate its feasibility.
  
  
  METHODS
  Four normal adult volunteers and six Sawbone elbow models were brought into this experiment. The kinematic data of five elbow flexion were collected respectively by optical positioning system. The rotation axes of the elbow joints were fitted by the least square method. The kinematic data and fitting results were visually displayed. According to the fitting results, the average moving planes and rotation axes were calculated. Thus, the rotation axes of new kinematic methods were obtained. By using standard clinical methods, the entrance and exit points of rotation axes of six Sawbone elbow models were located under X-ray. And The kirschner wires were placed as the representatives of rotation axes using traditional positioning methods. Then, the entrance point deviation, the exit point deviation and the angle deviation of two kinds of located rotation axes were compared.
  
  
  RESULTS
  As to the four volunteers, the indicators represented circular degree and coplanarity of elbow flexion movement trajectory of each volunteer were both about 1 mm. All the distance deviations of the moving axes to the average moving rotation axes of the five volunteers were less than 3 mm. All the angle deviations of the moving axes to the average moving rotation axes of the five volunteers were less than 5°. As to the six Sawbone models, the average entrance point deviations, the average exit point deviations and the average angle deviations of two different rotation axes determined by two kinds of located methods were respectively 1.697 2 mm, 1.838 3 mm and 1.321 7°. All the deviations were very small. They were all in an acceptable range of clinical practice.
  
  
  CONCLUSIONS
  The values that represent circular degree and coplanarity of volunteer's elbow single curvature movement trajectory are very small. The result shows that the elbow single curvature movement can be regarded as the approximate fixed axis movement. The new method can replace the traditional method in accuracy. It can make up the deficiency of the traditional fixed axis method.
authors.affiliation: The Fourth Clinical Medical College of Peking University, Department of Orthopaedics and Traumatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: W
authors.initials: W
authors.lastname: Han
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: J
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: G Z
authors.initials: GZ
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: H
authors.initials: H
authors.lastname: Ding
authors.affiliation: Peking University Health Science Center, Beijing 100191, China.
authors.forename: G S
authors.initials: GS
authors.lastname: Li
authors.affiliation: The Fourth Clinical Medical College of Peking University, Department of Orthopaedics and Traumatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: M Q
authors.initials: MQ
authors.lastname: Gong
authors.affiliation: The Fourth Clinical Medical College of Peking University, Department of Orthopaedics and Traumatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: X Y
authors.initials: XY
authors.lastname: Jiang
authors.affiliation: The Fourth Clinical Medical College of Peking University, Department of Orthopaedics and Traumatology, Beijing Jishuitan Hospital, Beijing 100035, China.
authors.forename: M Y
authors.initials: MY
authors.lastname: Wang
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004550:Elbow / Q000502:physiology*; D004551:Elbow Joint / Q000502:physiology*; D006801:Humans; D009068:Movement; D016059:Range of Motion, Articular; D012399:Rotation