Preoperative planning for pedicle subtraction osteotomy: Does pelvic tilt matter?

Study Design Multicenter, retrospective radiographic analysis. Objectives To evaluate the impact that preoperative spinopelvic parameters have on postoperative sagittal vertical axis (SVA). The researchers hypothesized that patients with a large preoperative pelvic tilt (PT) would require more extensive lumbar pedicle subtraction osteotomy (LPSO) procedures to reestablish anatomic postoperative SVA than patients with normal preoperative PT. Summary of Background Data Restoration of anatomic sagittal spinal alignment has been demonstrated to improve clinical outcomes. However, the degree to which spinopelvic parameters contribute to sagittal spinal malalignment is poorly understood. Methods Multicenter, retrospective analysis of 183 consecutively enrolled adult spinal deformity patients treated with LPSO procedures for correction of sagittal malalignment. Preoperative and postoperative freestanding full-length sagittal X-rays were analyzed for regional curves, pelvic parameters, and global alignment. Only patients with a preoperative SVA greater than 10 cm and a postoperative SVA less than 5 cm were retained for analysis. Patients were divided into 2 groups according to preoperative PT (low PT, less than 30°; and high PT, ≥30°). Independent t test analysis was used to determine differences in correction required to achieve postoperative SVA less than 5 cm. Results A total of 55 patients were identified for analysis. Low PT (n = 30) had lower preoperative PT than high PT (n = 25; 25° vs. 42°, respectively; p <.001). Analysis of the osteotomy performed demonstrated that the high PT group required a larger osteotomy resection (30° vs. 23°; p =.039) and a larger correction of lumbar lordosis (-43° vs. -31°; p =.006) to achieve an acceptable postoperative SVA (less than 5 cm). Conclusions This study demonstrates that patients with high PT in conjunction with sagittal spinal malalignment require larger lumbar osteotomy procedures, including a greater osteotomy resection and larger lumbar lordosis correction, to obtain a satisfactory postoperative SVA. Surgeons performing LPSO procedures must evaluate preoperative spinopelvic parameters, including PT, to avoid undercorrection and residual deformity after complex sagittal realignment procedures.