Figure 4.

(a) Preoperative x-rays of a thoracolumbar deformity patient from the compensated group (no cervical deformity). The magnitude of the cervical lordosis matches that of the T1 slope (TS-CL < 17°), demonstrating that there is good cervical compensation for the large global deformity allowing for horizontal gaze. (b) Postoperative x-rays of the same patient from the compensated group. Good global correction has been achieved and reciprocal change has occurred, with a decrease in the cervical sagittal alignment. The magnitude of the cervical lordosis remains in balance with the T1 slope. Abbreviations: CL, cervical lordosis; TS, T1 slope; TPA, T1 pelvic angle; CTPA, cervico-thoracic pelvic angle; C2-C7 PL, cervical plumb line; SVA, sagittal vertical axis.