The relationship between variation of preoperative coronal angle in the lumbosacral region and postoperative trunk shift after scoliosis surgery

The objective of this study was to investigate the relationship between the preoperative intervertebral interspace angle and postoperative trunk shift (TS) in patients who have received scoliosis correction. Anteroposterior (AP) whole spine standing radiographs and right and left lateral bending radiographs were taken preoperatively, and AP whole spine standing radiographs were obtained postoperatively and at the final follow-up. TS was measured in the coronal plane, and intervertebral interspace angle change was the sum of the absolute values of L4-S1 intervertebral angle changes in the coronal plane, and was determined before surgery, postoperatively, and at final follow-up. A total of 38 patients with a mean age of 16.42±8.36 years who received posterior scoliosis correction and internal fixation with a mean follow-up of 12.4 months (range, 6 to 25 months) were included. Groups were defined by two methods: bending angle > 10° and ≤ 10°, and postoperative TS < 20 mm and ≥ 20 mm. TS at the final follow-up was significantly greater in the > 10° group than the ≤ 10° group (32.45 vs. 12.44 mm, P = 0.001), and was significantly greater in the ≥ 20 mm group compared with the < 20 mm group (38.5 vs. 9 mm, respectively, P < 0.001). A median negative correlation were found between TS at the final follow-up and total variance of bending (r = -0.51, P = 0.001). Postoperative TS which will not compensate spontaneously can be predicted by measurement of the preoperative intervertebral interspace angle in the lumbosacral region.