The effect of 3-column spinal osteotomy on anterior pelvic plane and acetabulum position.

Because the spine and pelvis are integrated, changes in spine sagittal balance affect relative acetabulum position. A 1° change of the anterior pelvic plane changes acetabulum anteversion by 0.8°. Three-column spine osteotomies correct fixed sagittal plane deformity. Twenty patients with kyphotic deformity and associated sagittal imbalance underwent corrective 3-column osteotomy. We reviewed upright pelvic and spine radiographs preoperatively and postoperatively and documented the changes in angles. The average sagittal vertical axis was 11.07 cm preoperatively and 4.8 cm postoperatively. Lumbar lordosis changed (on average) from 39° preoperatively to 55° postoperatively (P < .05). Sacral slope increased an average of 6.7° (P = .015). Pelvic tilt decreased by 5.4° (P = .001). The anterior pelvic plane increased by 8.23° (P < .0001). This correction of the sagittal balance is associated with a concomitant increase in sacral slope, pelvic tilt, and the anterior pelvic plane angles. These changes will increase acetabulum anteversion by a predicted 6.54°. This increase will change acetabular cup position and must be considered in patients with spine and pelvic osteoarthritis that requires hip surgery.