Abstract
Discogenic pain accounts for approximately 40% of chronic low back pain cases, affecting 1 to 2 million adults between age 45 and 64 years in the United States. The putative pain generator in discogenic pain patients is usually considered intrinsic to the disc. Crock defined internal disc disruption as damage of internal disc structures while the external shape remains essentially normal, and no nerve root compression is present. However, the vertebral end plate is also a source of pain. It is the weak link during spinal compression, can sustain damage at loads well below those that cause disc herniation or vertebral fracture, and is innervated comparable to the outer annulus. Further evidence of the clinical importance of the vertebral end plate is the association between vertebral marrow abnormalities and discogenic pain. Data from multiple independent studies suggest that Modic Types I and II adjacent to the end plate are among the most specific of all MRI observations for predicting concordant discography-induced pain. In one prospective study, moderate-to-severe Modic Types I or II end plate abnormalities correlated 100% of the time with positive concordant pain at the adjacent disc. Recently, increased end plate innervation has also been reported for end plates with Modic changes.
End plates serve as the interface between rigid vertebral bodies and pliant intervertebral discs. Because the lumbar spine carries significant forces and discs do not have a dedicated blood supply, end plates must balance conflicting requirements of being strong to prevent vertebral fracture and porous to facilitate transport between disc cells and vertebral capillaries. Consequently, end plates are particularly susceptible to damage, which can increase communication between proinflammatory disc constituents and vascularized vertebral bone marrow. End plate damage regions can be sites of reactive bone marrow lesions that include proliferating nerves, which are susceptible to chemical sensitization and mechanical stimulation. While several lines of evidence indicate that innervated end plate damage can be a source of chronic low back pain, its role in patients is likely underappreciated because innervated damage is poorly visualized with diagnostic imaging. This literature review summarizes end plate biophysical function and aspects of pathologic degeneration that can lead to vertebrogenic pain.
Consultant for Relievant MedSystems
Consultant for Nocimed, LLC