Biomechanical evaluation of a novel intervertebral disc repair technique for large box-shaped ruptures

Mao-Dan Nie; Ze-Bin Huang; Ning-Ze Zhang; Ling-Jie Fu; Cheng-Kung Cheng

doi:10.3389/fbioe.2023.1104015

Biomechanical evaluation of a novel intervertebral disc repair technique for large box-shaped ruptures

Front Bioeng Biotechnol. 2023 Feb 8:11:1104015. doi: 10.3389/fbioe.2023.1104015. eCollection 2023.

Authors

Mao-Dan Nie¹, Ze-Bin Huang², Ning-Ze Zhang³, Ling-Jie Fu⁴, Cheng-Kung Cheng¹

Affiliations

¹ School of Biomedical Engineering and Engineering Research Center of Digital Medicine of the Ministry of Education, Shanghai Jiao Tong University, Shanghai, China.
² Department of Spine Surgery, First Affiliated Hospital of Second Military Medical University, Shanghai, China.
³ Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
⁴ Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

Abstract

Objective: The purpose of this study was to analyze the feasibility of repairing a ruptured intervertebral disc using a patch secured to the inner surface of the annulus fibrosus (AF). Different material properties and geometries for the patch were evaluated. Methods: Using finite element analysis, this study created a large box-shaped rupture in the posterior-lateral region of the AF and then repaired it with a circular and square inner patch. The elastic modulus of the patches ranged from 1 to 50 MPa to determine the effect on the nucleus pulposus (NP) pressure, vertical displacement, disc bulge, AF stress, segmental range of motion (ROM), patch stress, and suture stress. The results were compared against the intact spine to determine the most suitable shape and properties for the repair patch. Results: The intervertebral height and ROM of the repaired lumbar spine was similar to the intact spine and was independent of the patch material properties and geometry. The patches with a modulus of 2-3 MPa resulted in an NP pressure and AF stresses closest to the healthy disc, and produced minimal contact pressure on the cleft surfaces and minimal stress on the suture and patch of all models. Circular patches caused lower NP pressure, AF stress and patch stress than the square patch, but also caused greater stress on the suture. Conclusion: A circular patch with an elastic modulus of 2-3 MPa secured to the inner region of the ruptured annulus fibrosus was able to immediately close the rupture and maintain an NP pressure and AF stress similar to the intact intervertebral disc. This patch had the lowest risk of complications and produced the greatest restorative effect of all patches simulated in this study.

Keywords: annular patch; annular rupture; biomechanical evaluation; herniated disc; material properties.

Grants and funding

This work was supported by the Seeds Fund of Engineering Research Center of Digital Medicine of the Ministry of Education of Shanghai Jiao Tong University (Grant no. 20210407).