Serum biomarkers in patients with ossification of the posterior longitudinal ligament (OPLL): Inflammation in OPLL

BACKGROUD: Ossification of the posterior longitudinal ligament (OPLL) is characterized by replacement of ligamentous tissue by ectopic new bone formation. OPLL causes narrowing of the spinal canal, resulting in neurological impairment. However, the pathogenesis of OPLL has not been fully elucidated. We investigated whether inflammation occurs in OPLL or not using high-sensitivity CRP (hs-CRP) in a case-control study. METHODS AND FINDINGS: This study included 103 patients with OPLL in the patient group and 95 age- and sex-matched volunteers with degenerative spinal disease in the control group. Of the 103 OPLL patients, 88 patients who were available for more than 2 years follow-up were checked for OPLL progression. A blood sample was obtained and Hs-CRP, and other routine data, including total protein (TP), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), glucose (Glu), calcium (Ca), inorganic phosphate (Pi), white blood cell count (WBC), hemoglobin (Hb) and platelet (PLT), were analyzed. The data were compared between the patients with OPLL and the controls. The severity of the ossified lesions in the whole spine were evaluated by the ossification index (OS index) in patients with OPLL. The data were also compared between the patients with OPLL progression (the progression group) and the patients without OPLL progression (the non-progression group). In the results, the mean hs-CRP in the OPLL group was higher than that in the controls. The Pi in the OPLL group was lower than that in the control group. A negative correlation was found between the Pi and the OS index. The mean hs-CRP in the progression group was higher than that in the non-progression group. There was a positive correlation between the average length of the OPLL progression per year and the hs-CRP. CONCLUSIONS: The results may suggest the occurrence of local inflammation in OPLL and the inflammation might cause OPLL progression. These facts are important for understanding the pathology of OPLL.