Changes in ACL length at different knee flexion angles: an in vivo biomechanical study

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Anatomy

Background:

• Anatomical reconstruction of the anterior cruciate ligament (ACL) is a significant focus in orthopedic surgery.
• The double-bundle reconstruction technique for ACL injuries is increasingly advocated.
• Understanding the dynamic length changes of ACL bundles during knee motion is essential for surgical planning.

Purpose of the Study:

• To investigate how the lengths of individual anterior cruciate ligament (ACL) bundles change with varying knee flexion angles.
• To compare the length variations between different virtual ACL bundles (anatomical single bundle, anteromedial, posterolateral, and over-the-top).

Main Methods:

• High-resolution computed tomography (CT) scans were used to create 3D knee models from ten healthy subjects.
• Customized software facilitated digital length measurements of four virtual ACL bundles at fixed points on the femur and tibia.
• Length-versus-flexion curves were generated, and statistical analysis was performed for flexion angles of 0, 45, 90, and 135 degrees.

Main Results:

• All virtual ACL bundles reached their maximum length at full knee extension (0 degrees).
• The posterolateral bundle exhibited a significantly different length compared to other bundles at full extension.
• No significant length differences were observed between the anteromedial and over-the-top single bundles across all tested flexion angles.

Conclusions:

• Three-dimensional CT imaging is a viable method for assessing dynamic length changes in virtual ACL bundles.
• This approach enhances the understanding of ACL bundle function in clinical contexts, particularly for surgical reconstruction.
• Accurate assessment of bundle length variations can inform graft fixation strategies in ACL surgery.