Risk factors for acute proximal junctional kyphosis after adult spinal deformity surgery in preoperative motion analysis

This study aimed to examine which motion analysis parameters regarding the dynamic aspects and/or balance affect the development acute proximal junctional kyphosis (PJK) following adult spinal deformity (ASD) surgery. A total of 90 consecutive patients were recruited prospectively, who underwent a corrective surgery for ASD with sagittal imbalance. According to the development of acute PJK within 6 months after surgery, the patients were divided into the PJK+ and PJK− groups. Before surgery, three-dimensional gait analyses were performed using a motion analysis system. The preoperative continuous and categorical variables were compared between the PJK+ and PJK− groups using independent t tests and chi-square tests, respectively. Finally, a multivariate logistic regression model was used to identify the risk factors and calculate the odds ratio (OR) for acute PJK. A total of 20 and 70 patients were classified into the PJK+ and PJK− groups, respectively. There were no differences in the spinopelvic radiologic parameters pre- and postoperatively between the PJK+ and PJK− groups. The PJK+ group showed a significantly higher mean anterior pelvic tilt (Ant-PT) angle in preoperative motion analysis than the PJK− group (P = 0.001 for both sides). Multivariate analysis identified the mean Ant-PT angle (P = 0.047; OR 1.127; 95% CI 1.002–1.267) as a significant risk factor for acute PJK. Preoperative Ant-PT angle during walking was associated with a higher OR in acute PJK after surgery.