2015 ISAKOS Biennial Congress ePoster #1288

Elongation of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament (ACL) During the Dynamic Flexion-Extension Motion: Implication to Double-Bundle ACL Reconstruction

Yong Feng, MD, Boston, MA UNITED STATES
Tsung-Yuan Tsai, PhD, Boston, MA UNITED STATES
Jing-Sheng Li, MS, Boston, MA UNITED STATES
Xudong Liu, MD, Shanghai CHINA
Hai Hu, MD, PhD, Shanghai CHINA
Changqing Zhang, MD, Shanghai CHINA
Guoan Li, PhD, Boston, MA UNITED STATES

Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA

FDA Status Not Applicable

Summary: In double-bundle ACL reconstruction, the two grafts may need to be fixed at hyperextension in order to prevent over-stretching of the grafts.

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Abstract:

Background

The posterolateral (PL) graft has been reported to fail more frequently than the anteromedial (AM) graft in a double-bundle ACL reconstruction. We investigated the length changes of the two functional bundles of the ACL along the flexion-extension path of the knee to provide implications for improvement of double-bundle ACL reconstruction.

Hypothesis

The AM and PL bundles of the ACL continue to elongate at hyperextension of the knee.

Methods

Three-dimensional (3D) models of the knee were created for living knees of 10 male and 10 female subjects using their CT images, including the attachment areas of the two bundles of the ACL. Each bundle was represented by a straight line connecting its tibial and femoral attachment centroids. Each knee performed a dynamic flexion-extension cycle from hyperextension to a maximal flexion. Knee positions on the motion path were reproduced using a combined fluoroscopic imaging and CT modeling technique. The relative elongations of the AM and PL bundles of the ACL were calculated using the series of knee models along the motion path.

Results

The relative elongation patterns of the AM and PL bundles were distinctively different. At hyperextension, in average, the relative elongation of the PL bundle (5.52%) is higher than that of the AM bundle (5.04%). It was then sharply reduced to 1.86% at 0° and -0.63% at 10° of flexion of the knee. The relative elongation of the AM bundle slightly changed to 4.56% at 0° and 4.42% at 10° of flexion of the knee and was reduced to 0.70% at 30° of flexion. Both bundles consistently reduced their lengths at higher flexion angles.

Conclusion

The relative elongation of the PL bundle was highest at hyperextension while that of the AM bundle was highest between hyperextension and 10° of flexion during the dynamic flexion-extension cycle of the knee. These data may provide useful information for selection of graft fixation angles in a double-bundle ACL reconstruction.