Fig. 2

Measurement of the depth ratio and the coronal ratio. The triangle indicates the cage center. a Depth ratio = D/L. L (solid line) indicates caudal endplate length. D (double-arrowed line), parallel to L, is the distance between the cage center and the disc center. b Coronal ratio = D’/L’. L’ (solid line) indicates the distance between caudal pedicles. D’ (double-arrowed line), parallel to L’, is the distance between the triangle and the midline