The Accuracy and Advantages of Computer Navigation in High Tibial Osteotomy Kinzel Vera FRACS Parker David A FRACS Hanson Curtis MD Scholes Corey PhD Coolican Myles RJ FRACS 1 Sydney Orthopaedic Research Institute Australian Orthopaedic Association 70th Annual Scientific Meeting Adelaide, 2010

Conflict of interest We have no conflict of interest to report

High tibial osteotomy (HTO) Used to correct lower limb malalignment Alter mechanical axis of the lower limb Treatment for knee OA Unload damaged compartment Transfer load to healthy cartilage

HTO Planning and assessment Long-leg x-ray Pre and post-op Intraoperative Jig-CW Rod or cables Fluroscopy Limitations Accuracy Radiation Inconvenience

Computer navigation Increasing use in orthopaedic surgery Accuracy and reliability Established in arthroplasty past 4 years Real time information on coronal & sagittal plane alignment Utilised in osteotomy past 4 years

TKR Navigation Usage in Australia* *Source: Stryker Australia

Aim Compare the accuracy of the traditional form of preoperative assessment with intraoperative and postoperative assessment of the alignment utilising a computer-based navigation system.

Methods 20 Patients ( 2 female, 18 male) Average Age: 50.4 All varus alignment - HTO medial opening wedge

Methods Preop Long leg standing A-P xray Measured mechanical axis

Methods Intraop Percutaneous insertion of femoral and tibial tracker pins & registration of hip

Methods Intraop Arthroscopic registration of intraarticular landmarks via standard portals

Methods Intraop Registration of external landmarks Osteotomy performed under continuous measurements via navigation until desired alignment achieved

Methods Intraop femoral head allograft and plate fixation

Methods Postop long leg standing A-P xrays at 6 months postop.

Average lower limb alignment measured with x-ray and navigation Varus Valgus * * Significantly different to navigation (p<0.05)

Individual differences in alignment measurements pre and post-operatively

Discussion Navigation assisted surgery is becoming more popular in orthopaedic procedures This study demonstrates that use of navigation in osteotomy yields result comparable but not identical to those using long Leg X Rays alone

Conclusion Navigation is Safe Reliable. Real time information Useful for dynamic monitoring during lower limb osteotomies

Conclusion Navigation provides comparable information in determining existing malalignment postoperative correction in the coronal axis when compared to traditional methods

Thank you 20

Lower limb alignment measured with x-ray and navigation Varus Valgus

Differences in alignment measurements pre and post-operatively * * Significant difference between pre-op and post-op (p<0.05)

Differences in future measurements of alignment (+/- Prediction intervals)