2015 ISAKOS Biennial Congress ePoster #1289

Three-Dimensional CT Analysis of Posterolateral Femoral Tunnel in Double Bundle ACL Reconstruction. Comparison of Outside-In and Transportal Drilling Techniques

Shunichiro Kambara, MD, Nishinomiya, Hyogo JAPAN
Hiroshi Nakayama, MD, Nishinomiya, Hyogo JAPAN
Motoi Yamaguti, Nishinomiya, Hyogo JAPAN
Akio Matsumoto, MD, Nishinomiya, Hyogo JAPAN
Ken Sasaki, MD, PhD, Kobe, Hyogo JAPAN
Kaori Kashiwa, MD, Sasayama, Hyogo JAPAN
Tomoya Iseki, MD. PhD., Nishinomiya, Hyogo JAPAN
Shinichi Yoshiya, MD, Nishinomiya, Hyogo, Hyogo JAPAN

Hyogo College of Medicine, Nishinomiya city, Hyogo, JAPAN

FDA Status Cleared

Summary: Outside-in technique for PL femoral tunnel drilling may have advantage over transportal technique in reducing the gap between the graft and the bone tunnel wall at the intraarticular aperture; however, the graft bending angle at the aperture was more acute in outside-in drilling technique.




Optimal mode of femoral drilling technique in anatomic double bundle anterior cruciate ligament (ACL) reconstruction is still controversial. We have been performing double-bundle procedure suing semitendinosus tendon grafts, and anteromedial (AM) femoral tunnel has been drilled with outside-in (OI) technique to reduce the risk for complications such as posterior wall blow-out. By contrast, the risk for those tunnel-related complications is minimal for PL tunnel in both transportal and OI drilling techniques. Consequently, both methods are currently employed for PL femoral tunnel drilling in our practice. The purpose of this study was to compare the tunnel geometry between inside-out drilling via far anteromedial (FAM) portal and outside-in drilling method using three-dimensional image analysis on postoperative CT images.

Materials And Methods

Postoperative CT images at 1 week were available for analysis in 38 patients who underwent anatomic ACL reconstruction in our institutes. For the PL femoral tunnel drilling, transportal method via FAM portal was employed in 21 knees (FAM group) while OI drilling was performed in 17 knees (OI group). CT examination was performed with the knee in full extension. Thereafter, three-dimensional CT image analysis using ZioTerm2009?R imaging software was applied to the PL femoral tunnel and the following parameters were evaluated: position of the center of the PL tunnel, tunnel length, shape of the intraarticular aperture (major axis length of the ellipse in relation to the original drilling diameter), bending angle of the graft (angle formed by long axes of the intararticular graft and the femoral bone tunnel).


Assessment of the tunnel center location based on the Bernard and Hertel method showed that anatomic tunnel placement could be achieved in both groups without significant difference in percent height and depth values. The mean tunnel length was not significantly different between the groups. The major axis of the aperture/drill diameter ratio averaged 1.23 ± 0.13 in the FAM group and 1.12 ± 0.12 in the OI group. The calculated value was significantly larger in the FAM group indicating that the aperture shape was more elliptic in this group. The mean graft bending angle at the femoral tunnel aperture was 63.6° ± 6.9° in the FAM group and 99.4° ± 5.4° in the OI group showing significant intergroup difference.


The present study showed that anatomic placement of the PL femoral tunnel was feasible in both techniques. Demonstrated advantages of OI technique over inside-out transportal method included less tunnel coalition and more round aperture shape with decreased tunnel-graft gap at the aperture. These factors can help enhance tissue healing at the graft-bone tunnel wall interface; however, the graft bending angle at the tunnel aperture was more acute in the OI drilling group, which may increase the mechanical stress at the aperture. Comparative clinical outcome study seems required to identify the consequence of those geometric differences.