RESEARCH ARTICLE


Puncture of a Disc and Application of Nucleus Pulposus Induces Disc Herniation-Like Changes and Osteophytes. An Experimental Study in Rats



Kjell Olmarker*
Muskuloskeletal Research, Department of Medical chemistry and Cellbiology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden


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Creative Commons License
© Kjell Olmarker; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Muskuloskeletal Research, Department of Medical chemistry and Cellbiology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden; Tel: +46-31-7866660; E-mail: kjell.olmarker@gu.se


Abstract

It has been observed that puncture of a lumbar disc may induce formation of a nodule on the surface of the disc and osteophytes. It is not known if this is based on the presence of a foreign tissue or specifically by the presence of nucleus pulposus or on the disc injury. In this study these mechanisms were separated by comparing disc puncture with application of nucleus pulposus without disc injury, with superficial disc injury without nucleus pulposus and with application of fat. Fifty rats underwent facetectomy of the left L4-5 facet. Ten additional rats were used as donor rats. The rats were exposed to disc puncture (n=10), application of homologous nucleus pulposus (n=10), application of homologous fat tissue (n=10), superficial disc injury (n=10) and ten rats served as control. After 3 weeks the rats were examined macroscopically regarding presence of disc nodules and osteophytes. A limited histological analysis was performed to obtain a microscopic overview of any observed changes. In rats with application of fat, superficial disc injury and in sham controls there were almost no changes observed. However, in rats with disc puncture and applied nucleus pulposus there were clear disc nodules and osteophytes noted. Microscopically the nodules comprised granulation tissue and the osteophytes cortical bone. In conclusion, the data indicate that the presence of nucleus pulposus is more likely to be responsible for the formation of disc nodules and osteophytes than disc injury or the presence of a foreign tissue. This may provide new insights in the mechanisms regarding the formation of disc herniations and osteophytes.

Keywords: Spine, disc herniation, nucleus pulposus, disc injury, osteophytes, rat.