Fig. 3.

a Flèche cervicale and flèche lombaire presenting the sagittal alignment of the patient’s back. Both variables are measured as the sagittal distance between the lowest point of the cervical and lumbar spine, respectively, toward the plumb line. b Trunk inclination is measured as an angle between the line connecting the vertebral point (VP) and the midline of the right (DR) and left (DL) dimple points representing the spina iliaca (SI) of the upright standing patient toward the plumb line