Postoperative pelvic incidence (PI) change may impact sagittal spinopelvic alignment (SSA) after instrumented surgical correction of adult spine deformity (ASD)

To study factors causing postoperative change of PI after surgical correction of ASD and to assess the effect of this variability on postoperative PI-LL mismatch. PI is used as an individual constant to define lumbar lordosis (LL) correction goal (PI-LL 10°) associated with a |∆PI|> 6°, P = 0.05. Sacroiliac fixation diminished PI variability only during the first postoperative year. Preoperative variability and postoperative instability of PI diminish the applicability of the PI–LL