Spinopelvic parameters during gait revealed through biplane radiography

Spinopelvic alignment impacts hip mechanics and influences hip morphologies in healthy populations. Pelvic incidence (PI) and sacral slope (SS) are spinopelvic parameters that influence pelvic orientation, but their impact on gait is less understood. The objectives of this study were to investigate the relationships of PI with dynamic SS and hip kinematics during gait, and to identify sex-based differences in PI and SS.

Synchronized biplane radiographs of the hip were collected from 24 participants during walking, and subject-specific 3D bone models were created from CT images. Three-dimensional hip kinematics during gait were calculated after matching the bone models to the biplane radiographs using a validated registration process. PI was measured in CT images and SS was measured from 3D bone models. Pearson and Spearman correlation was used to identify associations between PI and SS and hip kinematics normalized to standing, and unpaired t-test and Wilcoxon rank sum test was used to identify sex-based differences in PI and SS.

There was a positive correlation between PI and maximum SS (ρ=0.671, p = 0.002) and minimum SS (ρ=0.639, p = 0.003) during gait. Greater PI was correlated with less maximum hip flexion (r = -0.365, p = 0.014) and more maximum hip extension (r = -0.407, p = 0.006) during gait. There were no sex-based differences in PI (p = 0.65) nor SS (p = 0.53).

PI and dynamic SS are associated with each other and with hip flexion and extension endpoints during gait. This provides insight into the relationship between static pelvis orientation from CT and dynamic pelvis and hip kinematics during gait.