Analysis of intervertebral disc degeneration in patients with ossification of the posterior longitudinal ligament

As degenerative disease with nerve compression, little is known about the relationship between cervical ossification of the posterior longitudinal ligament (OPLL) and intervertebral disc degeneration (IVDD). This study investigates the effect of ossification of ligaments on IVDD in patients with cervical OPLL. We focus on the ossification-related segment in patients diagnosed with OPLL, which is characterized by ossification that crosses intervertebral space or occurs concurrently in the upper and lower vertebrae.A total of 92 ossification-related segments from 40 patients were involved in the study. X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) were used to evaluate the ossification thickness, disc height, cervical range of motion (ROM) of the segment, Kang's grade, and disc signal loss. We conducted correlation analysis and subgroup comparisons to analyze the type of ossification, ossification thickness, disc height, disc signal loss, ROM and Kang's grade.The specific ossification thickness was negatively correlated with the disc signal loss (P<0.05). Specific ossification thickness and specific disc height were positively correlated (P<0.05). Segments were divided into the nude group (ossification not crossing the intervertebral space) and the covered group (ossification crossing the intervertebral space). The nude group presented smaller ossification thickness and disc height, and a higher grade of disc signal loss and ROM (P<0.05).The formation of OPLL may be interrelated with the alleviation of IVDD at the same segment. Furthermore, IVDD is not only related to the limited ROM caused by ossification, but also the size and shape of the ossified mass. A negative correlation exists between the ossification thickness and the severity of IVDD in OPLL patients. Ossification that crosses the interverbal space is associated with lower ROM, a thicker ossified mass, and better disc signal. For patients with nude ossification-related segments, a fusion surgery to restore intervertebral stabilization deserves serious consideration.