An animal model for discogenic low back pain

Low back pain is a debilitating condition that afflicts millions of people each year. It is characterized by complex biochemical, morphological, and biomechanical changes. However, most believe low back pain arises due to abnormal mechanical loading, inflammation, and disc degeneration. Several studies have investigated radial back pain, but to date, there is only one in vivo animal model for low back pain. Despite advances in science, the causes of low back pain remain unclear and treatments fail to relieve the pain. To better understand the causative factors of low back pain, a reliable animal model is needed. This study was designed to advance the knowledge of the previous in vivo animal model for low back pain by investigating the effects of shear loading on disc degeneration (for a longer duration of time) and discogenic low back pain (in terms of immunohistochemistry) in hopes developing better treatment strategies for low back pain sufferers and to help elucidate the etiology of low back pain.

Adult male Sprague Dawley rats (n=31) were shear loaded for 4- and 8- weeks. Pain behavioral testing was done prior to and after surgery. After sacrifice, immunohistochemistry was used to detect the presence of pain in the intervertebral discs and the spinal cord. Results of this study indicate that the application of an abnormal shear load gives rise to disc degeneration. Histology revealed that all loaded levels as well as the adjacent levels degenerated due to the shear load. Pain behavior testing revealed that the rats did experience pain, however, when combined with the immunohistochemical results, we were able to exclude the pain as pain stemming from the degenerated discs. Surprisingly, we observed that shear loading caused scoliosis of the thoracolumbar spine.