OrthoPilot® navigation of high tibial open wedge osteotomy with TomoFix™ plate and POSITION HTO plate

Project No. FF-FR 0150


completed 04/2014


The high tibial osteotomy is a well-established and commonly used treatment for active patients with medial unicompartmental osteoarthritis or cartilage lesion of the knee and varus malignment. Development of new implants and improvement of the surgical technique led to widespread use of the procedure. High complication rates are reported. The result depends on the precision of the correction, partially. Reports of an advantage of the navigation tool are available, however, the level of evidence was low. Primary biomechanical stability of implants and radiostereometry analysis encourage to early full weight bearing after open wedge HTO. Improvement of clinical scores could not be observed in published studies.

The purpose of the study was to examine the precision of the navigation compared to the digital planning in open wedge HTO. Primary outcome was the difference of the mechanical tibiofemoral angle (mTFA) compared the planning and the 6 weeks follow-up measurements (full weight bearing long leg radiographs). Secondary outcome was defined as clinical results depending on the different groups (surgical experience, aftercare, implant).


Overall n=120 patients were planed to include in the study (n=60 navigation and n=60 non navigation). The patients were randomized according the different groups. Open wedge HTO was performed according the well-known technique. The surgery was performed in n=60 cases by an experienced surgeon (consultant) and in n=60 by a non-experienced surgeon (resident). This assignment was not randomized. If the OrthoPilot® navigation tool was used the aim of the correction was guided by the navigation tool. If the surgical procedure was performed without the navigation tool the height of the osteotomy gap was measured and adjusted according the digital planning. Fixation was performed using the POSITION HTO plate or the TomoFix-plate. Postoperatively, the patients were allowed to full weight bearing after 6 weeks or after 11 days.


  • Complication rate of the POSITION HTO group was 44% (n=9 patients). Therefore the study arm was stopped immediately. The number of the patients of the study were expanded of these 9 patients with the TomoFix-plate.
  • No higher precision using the navigation tool OrthoPilot® was observed. The time of surgery was longer than without navigation.
  • Digital planning (medCAD®, Hectec) has a high precision.
  • Limited loss of correction was observed over the follow-ups.
  • Significant improvement of the clinical scores of all patients at different follow-ups was observed.
  • Significant improvement of the quality of life of the different items of the SF 36 was observed.
  • Advantage of the early full weight bearing after 11 days was observed during the first six months after surgery compared to the full weight bearing.
  • Significant superior results were observed in the group of early weight bearing of the SF 36.
  • No influence on the clinical outcome was observed of the groups: surgeon, navigation.

The POSITION HTO plate (Aesculap, Braun, Tuttlingen, Germany) represent short spacer plates and could not be recommended. Higher stability of the TomoFix-plate is known and recommended for fixation of the osteotomy. Using the navigation tool (OrthoPilot®) did not improve the precision of the osteotomy, however, the time of surgery was longer and the costs are higher. Early full weight bearing is recommended to improve the clinical outcome much earlier.

Last Update:

17 Nov 2015


Financed by:
  • Deutsche gesetzliche Unfallversicherung (DGUV)
Research institution(s):
  • BG Unfallklinik Tübingen

-cross sectoral-

Type of hazard:




Description, key words:

OrthoPilot, Osteotomy, TomoFix, POSITION HTO