Existence of pyogenic spondylitis in Modic type 1 change without other signs of infection: 2-year follow-up.

The relationship of Modic change to pain and inflammation remains to be unclear. Recently, some authors have reported that Modic type 1 signals are closely related to infection. However, if the patients do not have severe back pain, fever, or an abnormal blood profile, it is difficult to distinguish between common Modic change and infection. The purpose of this study was to examine the prevalence of pyogenic spondylitis in patients who showed Modic type 1 change without other signs of infection. Seventy-one patients with Modic type 1 change were evaluated (average age 55, 32 males and 39 females). X-ray and magnetic resonance imaging (MRI) were performed to investigate low-back pain and leg pain. Body temperature was measured and blood analysis (including white blood cell count and level of C-reactive protein) was conducted for all patents. All 71 patients with Modic type 1 change, but without other signs of infection were followed for 2 years. Low-back pain, X-ray, and blood analyses were performed every 3 months; and MRI was performed every year. Severe low-back pain or abnormal signs developed in four patients during the follow-up. Pyogenic spondylitis was diagnosed in three patients by symptoms, blood results, and imaging, and confirmed by biopsy. Two of the three patients were diabetic. A total of 4.2% of patients with Modic type 1 change, but without other signs of infection were diagnosed as having pyogenic spondylitis during the 2-year follow-up, therefore, it is important to consider this before treating Modic type 1 change.