Study design: Immunohistochemistry for tumor necrosis factor (TNF) and protein gene product (PGP) 9.5 in vertebral endplates of patients with discogenic low back pain and Modic Type 1 or Type 2 endplate changes on MRI.
Objectives: To examine whether inflammatory cytokines and nerve in-growth into the vertebral endplate are associated with discogenic low back pain.
Summary and background data: Degenerated discs and endplate abnormalities can be a cause of discogenic low back pain. However, the presence of TNF-immunoreactive cells and PGP 9.5-immunoreactive nerve fibers has not been studied in patients with discogenic low back pain and endplate changes on MRI.
Methods: Eighteen endplates showing either normal intensity signals on MRI (endplate change -), Modic Type 1 signals (low intensity on T1-weighted spin-echo images), or Modic Type 2 signals (high intensity) from patients with discogenic low back pain (n = 14) or controls requiring surgery for other back problems (n = 4; scoliosis and traumatic injury of vertebra) were harvested during surgery. Endplates were immunostained using antibodies to TNF and PGP 9.5 and immunostained cells and nerve fibers in the endplates were counted.
Results: Vertebral endplates from patients with Modic Type 1 or Type 2 endplate changes on MRI had significantly more PGP 9.5-immunoreactive nerve fibers and TNF-immunoreactive cells in comparison with patients with normal endplates on MRI (P < 0.01). The number of TNF-immunoreactive cells in endplates exhibiting Modic Type 1 changes was significantly higher than in endplates exhibiting Modic Type 2 changes (P < 0.05).
Conclusions: The results suggest that endplate abnormalities are related to inflammation and axon growth induced by TNF. TNF expression and PGP 9.5-positive nerve in-growth in abnormal endplates may be a cause of low back pain.