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A photoelastic study of ligament strain
S Hirokawa1, K Yamamoto, T Kawada
1Department of Graphic Science, Faculty of Engineering, Kyushu University, Fukuoka, Japan.
IEEE Transactions on Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
|September 28, 1998
Summary
Researchers measured anterior cruciate ligament (ACL) strain using photoelastic coatings. This method accurately captured complex ACL deformations during knee flexion, revealing strain patterns and fiber directions.
Area of Science:
- Biomechanics
- Biomaterials Science
- Orthopedic Research
Background:
- The anterior cruciate ligament (ACL) experiences significant strain (10-20%) during knee flexion, far exceeding typical elastic materials.
- The ACL's complex 3-D shape and insertion movements lead to highly variable deformations, challenging traditional measurement techniques.
Purpose of the Study:
- To develop and validate a method for quantifying strain distribution across the entire ACL.
- To analyze the mechanical behavior of the ACL during natural knee motion.
Main Methods:
- Utilized the photoelastic coating method with a high fringe-sensitivity polyurethane film to measure strain.
- Validated the technique on a custom knee joint model before applying it to an actual ACL during free flexion-extension.
- Employed a specially designed apparatus for natural knee movement observation.
Main Results:
- Photoelastic coatings accurately reflected ACL strain behavior with minimal impact on mechanical properties.
- Principal strain lines visualized on the ACL corresponded to its fiber directions.
- Observed a reciprocal strain function between anterior and posterior bundles and a zero-strain area near the tibial insertion.
Conclusions:
- The photoelastic coating method is a viable tool for measuring strain distributions on both model and actual ligaments.
- This technique provides novel insights into the complex biomechanics of the ACL during knee movement.