Integrated Strategies for Annulus Fibrosus Repair: Smart Biomaterials and Fabrication Technologies

Abstract

Low back pain, linked to nucleus pulposus degeneration and annulus fibrosus (AF) defects, is a significant cause of global disability. The AF’s multilayered structure supports the spine, but its limited self-repair capacity makes treating AF injuries and herniation difficult. Traditional surgical interventions like discectomy often fail to restore AF integrity, resulting in high reherniation rates. In response, biomaterial-based strategies have emerged as promising alternatives, aiming to replicate AF structure, deliver bioactive factors, and promote tissue regeneration. This review evaluates the composition, biomechanics, and pathophysiology of the AF, emphasizing the fundamental properties of available biomaterials, integration with host tissues, mechanical properties, and biomimetic microenvironments in AF tissue remodeling and repair. We examine recent advances in AF repair biomaterials, including natural and synthetic hydrogels, decellularized extracellular matrix, electrospun scaffolds, and emerging technologies like three-dimensional bioprinting. These materials provide mechanical reinforcement, enhance cell adhesion, and modulate the degenerative microenvironment through controlled drug or growth factor release, offering a comprehensive approach to address the challenges of AF repair.

Impact Statement

This review systematically expounds on the revolutionary role of innovative strategies based on biomaterials in the field of AF repair. By applying advanced materials such as smart hydrogels, electrospun scaffolds, decellularized matrices, three-dimensional bioprinted structures, and smart microneedles, the limitations of traditional surgical intervention have been overcome. These biomaterials possess excellent biological properties, enabling them not only to reconstruct biomechanical integrity through biomimetic microstructures but also to actively regulate the degenerative microenvironment through delivery. Such cutting-edge tissue engineering technologies significantly reduce the risk of reherniation, promote endogenous regeneration, and pioneer new technologies for functional and long-lasting AF repair. The synergy between materials science and tissue engineering marks a new frontier in spine medicine, offering scalable solutions to alleviate dysfunction caused by disc degeneration worldwide.