Three- dimensional microstructural reconstruction of the ovine intervertebral disc using ultra-high field MRI

Publication date: Available online 30 June 2018
Source:The Spine Journal
Author(s): Mirit Sharabi, Kelly R. Wade, Fabio Galbusera, Volker Rasche, Rami Haj-Ali, Hans-Joachim Wilke
BackgroundThe intervertebral disc (IVD) is a complex organ which acts as a flexible coupling between two adjacent vertebral bodies and must therefore accommodate compression, bending and torsion. It consists of three main components which are elegantly structured to allow this: the annulus fibrosus (AF), the nucleus pulposus (NP) and the end-plates (EP).PurposeThus far, it has not been possible to examine the microarchitecture of the disc directly in three dimensions in its unaltered state and thus knowledge of the overall architecture of the disc has been inferred from a range of imaging sources, or by using destructive methods.Study designA non-destructive ultra-high field MRI of 11.7T was used together with image analysis to visualize the ovine IVDs.MethodsThree-dimensional image stacks from eight IVDs harvested from sheep, half of which were 4-5 years old and the others approximately 2 years old were reconstructed and examined and their microstructure were imaged. The overall structure of the disc, including the average of 14 AF lamellae (9-28), NP and EP was then visualized with particular attention given to integrating elements as radial translamellar cross-links, AF-NP transition zone EP-AF integration and EP-NP insertion nodes (i.e. the connecting junctions between the EP and NP). Moreover, collagen fiber orientation was determined at different depths and locations throughout the annulus.ResultsIt was found that there was a clearer demarcation in the AF-NP transition zone of the younger discs compared to the older ones. This difference was reflected in the visibility of AF-NP and EP-AF integration. It was also possible to view the fiber architecture of the AF-NP integration in greater depth than was possible previously with histological techniques. These fibers were mainly observed in the younger discs and their length was measured to be of 2.6±0.2mm.ConclusionsThe present results provide a substantial advance in visualization of the three-dimensional architecture of an intact IVD and the integration of its components.



https://ift.tt/2Kps3sT