• Richard Bostelmann, Tamara Bostelmann, Adrian Nasaca, Hans Jakob Steiger, Frank Zaucke, and Christoph Schleich.
• Department of Neurosurgery, University Hospital of Düsseldorf, Moorenstrasse 5, Düsseldorf 40225, Germany. Electronic address: richard.bostelmann@med.uni-duesseldorf.de.
• Spine J. 2017 Feb 1; 17 (2): 196-202.

Background ContextOn a molecular level, maturation or degeneration of human intervertebral disc is among others expressed by the content of glycosaminoglycans (GAGs). According to the degenerative status, the disc content can differ in nucleus pulposus (NP) and annulus fibrosus (AF), respectively. Research in this area was conducted mostly on postmortem samples. Although several radiological classification systems exist, none includes biochemical features. Therefore, we focused our in vivo study on a widely spread and less expensive imaging technique for the cervical spine and the correlation of radiological patterns to biochemical equivalents in the intervertebral discs.PurposeThe aim of this pilot study was to (1) measure the GAG content in human cervical discs, (2) to investigate whether a topographic biochemical GAG pattern can be found, and (3) whether there is a correlation between imaging data (X-ray and magnetic resonance imaging [MRI] including delayed gadolinium-enhanced MRI of cartilage [dGEMRIC] as a special imaging technique of cartilage) and the biochemical data.Study Design/SampleWe conducted a prospective experimental pilot study.Patient SampleOnly non-responders to conservative therapy were included. All subjects were physically and neurologically examined, and they completed their questionnaires.Outcome MeasuresVisual analogue scale neck and arm, Neck Disability Index score, radiological parameters (X-rays, MRI, dGEMRIC), and the content of GAG in the cervical disc were assessed.MethodsAfter surgical removal of 12 discs, 96 fractions of AF and NP were biochemically analyzed for the GAG content using dimethylmethylene blue assay.ResultsA quantitative pattern of GAGs in the human cervical disc was identified. There were (1) significantly (p<.001) higher values of GAGs (µg GAG/mg tissue) in the NP (169.9 SD 37.3) compared with the AF (132.4 SD 42.2), and (2) significantly (p<.005) higher values of GAGs in the posterior (right/left: 149.9/160.2) compared with the anterior (right/left: 112.0/120.2) part of the AF. Third, we found in dGEMRIC imaging a significantly (p<.008) different distribution of GAGs in the cervical disc (NP 1083.3 ms [SD 248.6], AF 925.9 ms [SD 137.6]). Finally, we found that grading of disc degeneration in X-ray and MRI was significantly correlated with neither AF- nor NP-GAG content.ConclusionsThe GAG content in human cervical discs can be detected in vivo and is subject to a significantly (p<.05) region-specific pattern (AF vs. NP; anterior vs. posterior in the AF). Up to the levels of AF and NP, this is reproducible in MRI in dGEMRIC technique, but not in X-ray or standard MRI sequences. Potentially, the MRI in dGEMRIC technique can be used as a non-invasive in vivo indicator for disc degeneration in the cervical spine.Copyright © 2016 Elsevier Inc. All rights reserved.

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