Abstract
Abstract
Objectives
Back pain will be experienced by 70–85% of all people at some point in their lives and is linked with intervertebral disc (IVD) degeneration. The aim of this study was to 1) compare 3D internal strains in degenerate and non-degenerate human IVD under axial compression and 2) to investigate whether there is a correlation between strain patterns and failure locations.
Methods
9.4T MR images were obtained of ten human lumbar IVD. Five were classed as degenerate (Pfirrmann = 3.6 ± 0.3) and five were classed as non-degenerate (Pfirrmann = 2.0 ± 0.2). MR Images were acquired before applying load (unloaded), after 1 kN of axial compression, and after compression to failure using a T2-weighted RARE sequence (resolution = 90 µm). Digital Volume Correlation was then used to quantify 3D strains within the IVDs, and failure locations were determined from analysis of the failure MRIs.
Results
Average of axial strains were higher (p<0.05) in the degenerate samples compared to the non-degenerate (−3.4 vs-5.2%, respectively), particularly in the posterior and lateral annulus (−6.2 vs −3.6%, and −5.6 vs −3.5%, respectively). Maximum 3D compressive strains were higher (p<0.05) in the posterior annulus and nucleus regions of the degenerate discs compared to non-degenerate (−9.8 vs −6.2%, and −7.7 vs −5.5%, respectively). In all samples peak tensile and shear strains were observed close to the endplates. All samples failed through the endplates with fractures in the nucleus region in all non-degenerate samples, and fractures in the lateral annulus regions in all degenerate samples.
Conclusion
Degeneration caused significant changes to strain distributions within IVDs, particularly at the lateral and posterior AF regions. A shift from endplate failure in the nucleus to the annulus region was observed which was also seen in peak axial internal strains demonstrating a possible correlation between internal IVD strains, and endplate failure locations.
Declaration of Interest
(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
