gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie
74. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie
96. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie
51. Tagung des Berufsverbandes der Fachärzte für Orthopädie und Unfallchirurgie

26. - 29.10.2010, Berlin

Determination of the kinematics of the aequos G1 knee endoprosthesis based on fluoroscopy

Meeting Abstract

  • M. M. Wachowski - Universitätsmedizin Göttingen, Unfallchirurgie, Plastische und Wiederherstellungschirurgie, Göttingen, Germany
  • H. Pandit - University of Oxford, Nuffield Department of Orthopaedic Surgery, Oxford, United Kingdom
  • H. S. Gill - University of Oxford, Nuffield Department of Orthopaedic Surgery, Oxford, United Kingdom
  • D. W. Murray - University of Oxford, Nuffield Department of Orthopaedic Surgery, Oxford, United Kingdom
  • D. Kubein-Meesenburg - Universitätsklinikum Göttingen, Kieferorthopädie, Göttingen, Germany
  • K.-H. Frosch - Universitätsmedizin Göttingen, Unfallchirurgie, Plastische und Wiederherstellungschirurgie, Göttingen, Germany
  • Biomechanische Arbeitsgruppe Oxford/Göttingen

Deutscher Kongress für Orthopädie und Unfallchirurgie. 74. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 96. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie, 51. Tagung des Berufsverbandes der Fachärzte für Orthopädie. Berlin, 26.-29.10.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocIN21-1097

DOI: 10.3205/10dkou127, URN: urn:nbn:de:0183-10dkou1271

Veröffentlicht: 21. Oktober 2010

© 2010 Wachowski et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objective: Conventional knee-endoprostheses show modified kinematics in comparison with the human knee. There is high percentage of sliding during the movement, which causes higher stress on the material compared to the physiological rolling. Despite of good clinical results the durability and patient satisfaction is higher after implantation of total hip endoprostheses. Minor differences in the kinematics of prostheses and physiologic joint in the hip may be the reason.

The construction of the Aequos G1 knee endoprosthesis is intended to provide a higher rolling-percentage. This has not been proven in vivo yet.

The kinematics of knee endoprostheses can be evaluated in vivo by fluoroscopy. In this study a new method of analysis is presented. The kinematics can be analysed by matching 3D-CAD-models of the implants with 2D-fluoroscopic images.

Methods: Fluoroscopic images (8 F/s) were recorded in lateral projection. The patient was instructed to perform a step-up exercise and a weight bearing deep knee bend starting from approximately 80°. Prior to each measurement a reference object was imaged to correct the physically caused distortions digitally. Based on CAD-models of the implant components synthetic silhouettes are generated, which are fitted to the fluoroscopic images using a random search algorithm. Now the 3D-position of each component can be calculated. Knowing the position of the tibial component the surface of the inlay can be determined. Using this data the calculation of the kinematics is performed.

11 Aequos G1 endoprostheses in 9 patients (6 female, 3 male, age: 66,8±5,6 years) were analysed at least 12 months after surgery.

Results and conclusions: The method described above allows conclusions to the points of contact on the surface of the components. Furthermore it is possible to analyse the variation in the patella tendon angle (PTA) and the knee flexion angle (KFA), which is a well established method for the determination of the kinematic profile (KP=ΔPTA / ΔKFA). Based on static pre-measurements a KP of 0,27 could be calculated, which is near the physiologic 0,3.

Preliminary examination of the data suggests that the Aequos G1 is capable of reproducing some features of normal knee kinematics, detailed analyses and the comparison with normal knees and other prosthesis models are currently being performed. The final results will be presented at the meeting.