Facet tropism and facet joint orientation: risk factors for the development of early biochemical alterations of lumbar intervertebral discs  C. Schleich, A. Müller-Lutz, K. Blum, J. Boos, B. Bittersohl, B. Schmitt, J. Gerß​, F. Matuschke, H.-J. Wittsack, G. Antoch, F. Miese  Osteoarthritis and Cartilage  Volume 24, Issue 10, Pages 1761-1768 (October 2016) DOI: 10.1016/j.joca.2016.05.004 Copyright © 2016 Terms and Conditions

Fig. 1 Axial T2 reference image for FJ measurements relative to the coronal plane (horizontal line). Coronal reference plane was defined by posterior aspect of the vertebral body or disc space. A second line was defined through the anteromedial and posterolateral margins of each FJ. FJ angle relative to the coronal plane was calculated. Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions

Fig. 2 MTRasym values [%] of no, mild and moderate + severe FT groups for NP and AF. For NP, all groups revealed significantly different gagCEST values with the lowest GAG concentration in the group with moderate + severe FT. For AF, only the groups no FT and moderate + severe FT demonstrated significantly different gagCEST values. Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions

Fig. 3 MTRasym values [%] of pooled data, no + mild FT and moderate + severe FT, for NP and AF. For both, NP and AF, moderate + severe FT demonstrated significantly lower gagCEST values compared to no + mild FT. Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions

Fig. 4 Pearson correlation coefficient demonstrated a significant negative correlation between gagCEST values and FJ angles for NP and AF (NP: r = −0.46, P < 0.0001; AF: r = −0.27, P = 0.017). Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions

Fig. 5 MTRasym values [%] of FJ orientation for NP and AF. For NP and AF, segments with an increased sagittal FJ orientation of more than 45° showed significantly lower GAG content compared to segments with an FJ orientation <45°. The presence of FT had no higher impact on biochemical GAG content of lumbar IVDs as compared to a sagittal FJ orientation larger than 45° in our study collective. Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions

Fig. 6 Sagittal T2w images with an overlaid MTRasym color map illustrating the gagCEST effect of the four different FJ orientation groups: a) <45°, no FT, b) <45°, FT, c) >45°, no FT, d) >45°, FT. Colour coding indicates high GAG content (red) to low GAG content (blue). Among the different groups, we found a decrease in GAG content from a to d. We could demonstrate the lowest gagCEST values in the group with FJ orientation >45° in combination with FT (image d) and an increase of GAG content with the highest gagCEST values in the group with FJ orientation <45° and no FT (image a). Additionally, among one participant (image a), GAG concentration varies between the different IVD levels with lower GAG concentration of the IVD with increased sagittal FJ orientation (in this example IVD of L3/4). Osteoarthritis and Cartilage 2016 24, 1761-1768DOI: (10.1016/j.joca.2016.05.004) Copyright © 2016 Terms and Conditions