was obtained with C-arm of Arcadis Orbic (Siemens,Germany). The image was transferred to a navigationsystem (StealthStation navigation system, Medtronic,Louisville, CO) and reconstructed into a 3D image of thedistal femur. During placement of guide wires for fem-oral tunnels through an accessory medial portal, a fem-oral guide with a tracker feed backed surgeons the di-rection of the guide wire on the 3D femur bone surfaceimage with real time fashion. The femoral guide wasplaced at the center of the footprint with help of visualguidance of the navigation as well as an arthroscopicview. Then, flexion angle of the knee was adjusted toprevent posterior blowout on the computer screen duringinsertion of the guide wire. The length of the femoraltunnel could also be estimated before over drilling theguide wire. This technology assists surgeons to place twofemoral tunnels precisely without any complication dur-ing anatomic double-bundle ACL reconstruction.

Paper 154: Navigation Evaluation of Pivot Shift Dur-ing Anatomical Double-bundle ACL ReconstructionYASUYUKI ISHIBASHI, MD, JAPAN, PRESENTING AUTHOR

EIICHI TSUDA, MD, JAPAN

AKIRA FUKUDA, MD, JAPAN

YUJI YAMAMOTO, MD, JAPAN,HAREHIKO TSUKADA, MD, JAPAN

SATOSHI TOH, MD, JAPAN

ABSTRACTObjective: Anterolateral rotatory instability (pivot shift)causes disability in anterior cruciate ligament (ACL)deficient knees, and sometimes even in ACL recon-structed knees. Therefore the interest that double-bundleACL reconstruction (DB-ACLR) that reproduces antero-medial (AM) and posterolateral (PL) bundles of the ACLhas risen. However, it is still unknown which of the AMand PL bundle is more important to prevent pivot shiftphenomenon. The purpose of this study was to assesswhich bundle prevents pivot shift during DB-ACLR us-ing a navigation system.Materials and Methods: Eighty patients, who receivedDB-ACLR using a navigation, were included in thisstudy. Their mean age was 21.3 years. During DB-ACLR, pivot shift tests were performed four times atbefore reconstruction, and at after only PLB fixation,only AMB fixation, and both PLB and AMB fixation.Tibial internal rotation and anterior translation weremeasured at each phase by the additional functions of thenavigation. The navigation system used in this study wasOrthoPilot ACL ver 2.0 (B/Braun Aesculap, Germany),which was image-free navigation.

Results: Before ACL reconstruction, tibial internal rota-tion and anterior translation were 22.9�7.6° and5.4�2.5mm. After PLB fixation, internal rotation andanterior translation significantly decreased to 19.5�7.5°and 2.2�0.9mm. After AMB fixation, they both de-creased to 21.6�6.7° and 2.4�0.9mm. After PLB andAMB fixation (DB-ACLR), these data were improved to19.0�7.3° and 2.0�0.7mm.Conclusions: Although it is well known that the ACL isa primary restraint of the knee under anterior tibial load,the role of the ACL in resisting internal tibial torque andthe pivot shift test is controversial. To our knowledge,this is the first study which assess the functions of AMand PL bundle of ACL to prevent pivot shift phenome-non in vivo. Our data indicate that both AMB and PLBplay a role in restraining not only anterior translation butalso internal rotation during pivot shift test, and DB-ACLR improves knee stability. These findings are alsoconsistent with previous in-vitro biomechanical studies,which measured in-situ forces of each bundle of theACL.

Paper 155: Measurement of Anteroposterior and Ro-tational Stability of Knee using Navigation SystemEUN KYOO SONG, MD, KOREA, PRESENTING AUTHOR

TAEK RIM YOON, MD, SOUTH KOREA

YOUNG JIN KIM, MD, SOUTH KOREA

CHANG ICH HUR, MD, SOUTH KOREA

KYUNG SOON PARK, MD, SOUTH KOREA

DAM SEON LEE, MD, SOUTH KOREA

JONG KEUN SEON, MD, SOUTH KOREA

SANG JIN PARK, MD, SOUTH KOREA

ABSTRACTPurpose: The aim of study was to provide normal valueof anteroposterior and rotational stability of knee jointsusing navigation system.Materials and Methods: From March 2007 to Novem-ber 2007, 35 patients (23 men, 12 women) with a meanage of 36.1(16-57) years, who were treated with arthros-copy, without ligament injury of knee were included inour study. We measured amount of anteroposterior dis-placement and rotation of the knee in 0, 30, 60 and 90degrees of flexion position using Orthopilot navigationsystem. All tests were performed by same single surgeonunder manual maximal force.Results: The mean anterior displacement was 3.7�2.0,6.6�2.2, 5.8�2.0 and 4.7�1.8 mm in 0, 30, 60 and 90degrees of flexion respectively. The amount of anteriordisplacement at 30 degree of flexion was significantlylarger than those of other degrees. The mean posteriordisplacement was 2.0�0.5, 2.2�0.4, 2.1�0.4 and

e426 ABSTRACTS