Fig. 1

Consistent group. A 60-year-old female patient who underwent unilateral open-door laminoplasty for inconsistent cervical ossification of the posterior longitudinal ligament (OPLL). a, c, e K-line (+), no increased signal intensity on T2-weighted imaging (T2WI). The left side had a larger ossification occupancy area (the ossification structure of the OPLL was divided into larger and smaller sides by the median sagittal line at the thickest ossified part in the CT axial image). b Radiograph at two years after surgery showing a decreased C2–7 Cobb angle. d The side of the open door was on the left side, consistent with the larger ossification occupancy area side. f T2WI at two years after surgery, showed that increased spinal cord diameter and spinal cord drift were more significant