Classification Of Annular Tears
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The patho-anatomy and physiology of chronic back pain is thought to be due to a combination of complex conditions that result in pain from chemical as well as mechanical factors arising from the disc and annulus.
The disc is an innervated structure that is capable of pain generation from the end plate, outer one third of the annulus, and the posterior longitudinal ligament. The posterior longitudinal ligament and annulus contain unmyelinated pain nociceptors that transmit and relay afferent pain signals through the dorsal root ganglion.
Substance P is released by the degenerating disc through annular tears that can cause chemical irritation of myelinated spinal nerves, resulting in sciatica and with back pain. These annular tears allow the ingrowth of granulation tissue and small unmyelinated nerve ﬁbers into the nucleus, theoretically differentiating the painful degenerative disc from an asymptomatic degenerative disc. However, the pain pattern, when not in a dermatomal pattern, is poorly understood, and patients with discogenic pain are frequently frustrated by their physician's focus on functional causes when their sciatica is not correlated with known dermatomal patterns.