genALIGN^M - Implementation and Evaluation of a novel Instrument for minimal-invasive Total Knee Arthroplasty


  • Determination of the mechanical femoral axis for prosthesis alignment in Total Knee Arthroplasty (TKA) based on purely mechanical force-torque-measurement.
  • Less invasive and more accurate than intramedullary alignment guides and lower-cost than computer assisted navigation systems.
  • Compared to the electronic system currently developed in the OrthoMIT project, no additional peripheral devices such as evaluation electronics, PC and monitor, reduced costs and simplified sterilization process.
  • Optimization of the system with regard to usability and risk management.


  • The surgeon applies a compressive force to the knee using the genALIGN device.
  • Resulting shear forces and torques are directly displayed to the surgeon by mechanical means.
  • When these forces and torques become zero, the device is aligned with the mechanical femur axis.

Final Report


The Project genALIGN^M is funded by the European Union as part of the European Regional Development Fund.
(Project term: 4/2009-6/2011)


  • F. Zimmermann, C. Schwenninger, U. Nolten, F.P. Firmbach, R. Elfring & K. Radermacher: A new approach to implant alignment and ligament balancing in total knee arthroplasty focussing on joint loads. Biomed Tech (Berl), 2012, 57(4), pp. 283-291
  • F. Zimmermann: Implantatpositionierung und Weichteilbalancing der Knieprothese unter Fokussierung auf die Gelenkbelastung, Deutscher Kongress für Orthopädie und Unfallchirurgie, 23.-26. Oktober, 2012, eingeladener Vortrag
  • F. Zimmermann, M. Asseln, B. Rath & K. Radermacher: Three challenges of TKA – one force-torque-based solution: the genALIGN system. 13th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery, 2013, pp. 192-193
  • US Patent No. 8308730 erteilt – Method of and apparatus for determining the mechanical axis of a femur – Nov 2012