Anterior cruciate ligament (ACL) injuries are common, especially among athletes. Each year, over 400 000 ACL reconstruction (ACLR) surgeries are carried out globally. While the success rate of ACLR is reported to be over 90%, a significant number of patients still face issues like revision surgery and long-term osteoarthritis. This has spurred research into better graft materials, and artificial ligaments have emerged as a potential solution. A recent review article published in Engineering delves into the current state and future prospects of artificial ligaments for ACLR.

Artificial ligaments have been in use since the 1950s. They offer advantages such as eliminating donor-site morbidity and the risk of disease transmission, which are associated with autografts and allografts. However, they also have drawbacks. Some artificial ligaments have shown a high incidence of complications like chronic effusions, synovitis, and graft failure. For example, the Gore-Tex ligament, made of PTFE, has had issues with a declining Lysholm score over time and a relatively high rate of graft failure, effusion, and infection.

The healing process of a reconstructed ACL involves two crucial parts: graft–bone integration inside bone tunnels and intra-articular ligamentization. Autografts are considered the gold standard due to their bioactive properties that facilitate cell adhesion, proliferation, and osteogenesis. In contrast, artificial ligaments often lack these bioactive features, which has led researchers to focus on enhancing their bioactivity.

In recent years, there have been numerous attempts to modify artificial ligaments and fixation devices. One approach is to add bioactive components to ligament scaffolds. For instance, adding ECM components like hyaluronic acid and collagen can enhance cell adhesion and proliferation. Another promising modification is the use of magnesium-based materials in fixation devices. Magnesium has been shown to promote osteogenesis by increasing the release of calcitonin gene-related polypeptide (CGRP), which in turn upregulates osteogenic genes.

The review also points out that future research on artificial ligaments should focus on several key areas. Advanced manufacturing processes such as electrospinning and 3D printing could improve the physical and biological properties of artificial ligaments. Direct modification of materials, like using natural silk with its good mechanical properties and cell affinity, holds great potential. Additionally, understanding the biological features of components and their key upstream biological effects is essential for optimizing artificial ligaments.

Although there are still challenges in balancing the mechanical and biological properties of artificial ligaments, these recent advancements bring hope for better clinical outcomes in ACLR. As research continues, artificial ligaments may one day provide a more effective and reliable alternative to traditional grafts.

The paper “Current Advances of Artificial Ligaments for Anterior Cruciate Ligament Reconstruction: From Biocompatibility to Bioactivity,” authored by Haozhi Zhang, Xin Chen, Michael Tim-Yun Ong, Lei Lei, Lizhen Zheng, Bingyang Dai, Wenxue Tong, Bruma Sai-Chuen Fu, Jiankun Xu, Patrick Shu-Hang Yung, Ling Qin. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.10.018. For more information about the Engineering, follow us on X (https://twitter.com/EngineeringJrnl) & like us on Facebook (https://www.facebook.com/EngineeringJrnl).