Towards bio-mimetics of the anterior cruciate ligament using collagen fiber reinforced bio-composites

The Anterior Cruciate Ligament (ACL) is one of the four knee ligaments responsible for the stability of the joint. Although approximately 300,000 anterior cruciate ligament (ACL) reconstructions are performed in the USA alone each year¹, proper ACL repair is not available to date. Since the use of “Gold Standard” autograft solutions available today (i.e. patellar tendon, hamstring tendon etc.) can result in a deficiency in knee joint function^2-3, a need arises for the design of a biocompatible implant that can mimic the native mechanical behavior of the ACL.

From a mechanical standpoint, the ACL is a composite material, composed of stiff collagen fibers embedded in a proteoglycans matrix. The mechanical behavior of the ACL is nonlinear with large deformations. Our research aims to mimic that mechanical behavior by fabricating a collagen fiber reinforced biocomposite⁴ ACL implant. Extracted from soft corals, our ultra-long collagen fibers are arranged unidirectionally and embedded in an alginate hydrogel to mimic the structure of the native ACL. The mechanical behavior of the bio-composite ACL is compared experimentally with the tensile behavior of native human ACL specimens and a 3D hyperelastic finite element knee model.

Our goal is to understand the effects of the ACL’s structure on its mechanical behavior under physiological loading and eventually mimic it using our biocomposites, for future ACL repair and replacement.

References:

1. Chechik, O. et al. International Orthopaedics 37, 201-206 (2013).
2. Gollquist, J. & Messner, K. Sports Med 27, 143-156 (1999)
3. Stefan, L. et al. The American Journal of Sports Medicine 35, 1756-1769 (2007)
4. Sharabi, M. et al. Journal of the Mechanical Behavior of Biomedical Materials 36, 71-81 (2014).