Possible role of autoimmune reaction in Modic Type I changes.

Modic changes (MCs) are common abnormalities in the vertebral endplates and adjacent bone marrow, which are visible on magnetic resonance imaging. They are regarded as having a strong association with the clinical symptom of low back pain (LBP). Nevertheless, the general pathogenesis of MCs is still under discussion. MCs can be divided into three types. Type I MCs represent extensive subchondral bone edema and vascular granulation tissue within the bone marrow of the adjacent endplate. The reasons for the edema and vascularization in Type I MCs, which may be the major mechanism underlying LBP, remain unclear. Chronic repetitive shear forces on the endplates lead to local disruption and microfractures. Following a breach of the outer annulus fibrous, the nucleus pulposus (NP) may enter the vertebral body. We hypothesize that the consequent autoimmune response due to a foreign body may cause and promote the development of edema, vascularization and inflammation, which are characteristic of Type I MCs. The production of cytokines evoked by autoimmunity could therefore be responsible for the significant clinical symptoms of LBP. If this underlying etiological pathway is proven, MCs and the consequent LBP could be treated by novel clinical methods.