Analysis of pelvic compensation for dynamic sagittal imbalance using motion analysis

Purpose To analyze pelvic compensation during walking in patients with severe sagittal plane deformity by using motion analysis. Methods A total of 44 patients with sagittal plane deformity who were scheduled to undergo surgery were included. Motion analysis was performed 3 consecutive times during walking to estimate the anterior pelvic tilt (Ant-PT) angle, trunk kyphosis (TK) angle, and distance of the center of gravity (CoG) from the center of mass (CoM) of the pelvic segment, and hip and knee joint angles during gait. The patients were classified into Ant-PT+/Ant-PT−, TK+/TK−, and CoG+/CoG− groups according to the changes in Ant-PT angle, TK angle, and distance of the CoG from the CoM of the pelvic segment. Increases and decreases in the values of the variables from the first trial to the third trial were indicated with “+” and “−” signs, respectively. Results The mean Ant-PT angle, TK angle, and distance of the CoG from the CoM of the pelvic segment increased progressively, and the differences in the values of these variables from the first to the third trials were statistically significant ( P = 0.046, P = 0.004, and P = 0.007 for the Ant-PT angle, TK angle, and distance of the CoG from the CoM of pelvic segment, respectively). Among the 44 patients, 27 and 34 were classified into the Ant-PT+ and CoG+ groups, respectively. Older age and higher body mass index (BMI) were significantly associated with the Ant-PT+ group. The CoG+ group demonstrated a significantly higher height and weight than the CoG− group. Conclusions Higher BMI, height, and weight are risk factors for progressive worsening of dynamic sagittal imbalance. Graphic abstract These slides can be retrieved under Electronic Supplementary Material.