Fig. 4

Effects of intervertebral rotation and translation on COR (Y). a–c The angle between the two tangents of the posterior edge of the superior vertebral bodies in flexion and extension positions is defined as the ROM of the target FSU (White method [43]). a The ICR is located within the disc in the case of intervertebral motion with only rotation. b The ICR is located far below the disc in intervertebral motion with only translation. c Because the physiological intervertebral motion consists of both rotation and translation, the COR in the superior–inferior direction is located between the rotation ICR and the translation ICR. A, anterior; P, posterior