BackgroundTo investigate the effectiveness and feasibility of a novel vertebral osteotomy technique, transpedicular opening-wedge osteotomy (TOWO) for correcting rigid thoracolumbar kyphotic deformity in patients with ankylosing spondylitis (AS).Methods18 AS patients underwent TOWO for correcting rigid thoracolumbar kyphosis. Radiographic parameters were compared before surgery, 1 week after surgery and at last follow-up. SRS-22 questionnaire was assessed before surgery and at last follow-up to evaluate clinical improvement. The operating time, estimated blood loss and complications were analyzed. ResultsThe mean operating time and estimated blood loss were 236 minutes and 595 ml, respectively. Sagittal parameters improved significantly after surgery. The height of anterior column of osteotomized vertebrae was increased significantly at 1 week after surgery and last follow-up when compared to preoperative, but the height of middle column did not changed significantly. SRS-22 scores were improved significantly at last follow-up than preoperative. Solid fusion was achieved in all patients after 12 months follow-up, no screw loosening, screw pull out or rod breakage was noticed at last follow-up. ConclusionsTOWO could achieve a satisfactory kyphosis correction by opening anterior column instead of vertebral body decancellation and posterior column closing, which simplified the osteotomy procedure and improved the surgical efficacy.

Background: Ankylosing spondylitis (AS) patients with kyphosis have an abnormal spinopelvic alignment and pelvic morphology. Most of them focus on the relationship of pelvic tilt (PT) or sacral slope (SS) and deformity, and relatively few studies have addressed the relationship between pelvic incidence (PI) and kyphosis in AS patients. The purpose of this study is to analyze the correlation between pelvic incidence (PI) and the spinopelvic parameters describing local deformity or global sagittal balance in AS patients with thoracolumbar kyphosis. Methods: A total of 94 patients with AS (91 males and 3 females) and 30 controls were reviewed. Sagittal spinopelvic parameters, including PI, PT, SS, thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis(LL), sagittal vertical axis(SVA), T1 pelvic angle(TPA), spinosacral angle(SSA) and spinopelvic angle(SPA) were measured. Statistical analysis was performed to identify the correlation of PI with other parameters. Results: Compared with the control group, the AS patients had significantly higher PI(47.4˚ vs. 43.2˚, P<0.001). PI in AS patients was found to be significantly positively correlated with TPA(r=0.533, R 2 =0.284, P<0.001), and negatively correlated with SPA(r=-0.504, R 2 =0.254, P<0.001). However, no correlations were found between PI and SVA, SSA, TK, TLK or LL in AS patients. Conclusion: The value of PI in AS patients with kyphosis was significantly higher than that of controls. Correlation analysis revealed that increasing PI was significantly correlated with more global sagittal imbalance, not with the local deformity in AS patients with thoracolumbar kyphosis.