OP3.6 Sex-based Differences in Pelvis Orientation During Gait Revealed Through Biplane Radiography

Background: Pelvic orientation impacts hip joint mechanics and the pathomechanics of non-arthritic hip disorders. Pelvic incidence, a measurement of the relationship between the spine and acetabulum, has also been shown to influence pelvic tilt, but its impact on gait is less well understood. Similarly, sex-based differences in pelvic orientation during gait remain elusive. In vivo quantification of dynamic pelvic orientation during gait would improve our overall understanding of hip mechanics.

Questions/Purposes: (1) Is pelvic incidence related to sacral slope during gait? (2) Is pelvic incidence related to femoroacetabular kinematics during gait? (3) Are pelvic kinematics during gait different between men and women?

Methods: Twenty-four participants (11 men, 13 women; age 22 ± 2 years) were enrolled in this study. Synchronized biplane radiographs were collected at 50 images/sec during treadmill walking. 3D bone models were created from bone tissue segmented in the CT images acquired for each participant, and a validated volumetric model-based tracking technique was used to match digitally reconstructed radiographs created from the bone models to the distortion-corrected biplane radiographs. Pelvis kinematics during gait were calculated to produce a single kinematic waveform for each participant. Pearson correlation was used to identify associations between pelvic incidence and sacral slope and femoroacetabular kinematics. Sex-based differences in pelvis kinematics waveforms during gait were identified using statistical parametric mapping (SPM) using unpaired t-test.

Results: There was a positive correlation between pelvic incidence and maximum sacral slope (p = 0.001) and minimum sacral slope (p = 0.001) during gait. Greater pelvic incidence was correlated with less maximum hip joint flexion (p = 0.014) and more maximum hip joint extension (p = 0.006) during gait. During mid-stance, women demonstrated greater contralateral hip drop than men (p < 0.001) with an average difference of 2.4°.

Conclusions: Greater pelvic incidence is associated with greater sacral slope and decreased femoroacetabular flexion during gait. Women exhibit greater pelvic obliquity during the stance phase of gait than men. These kinematics findings provide insight into the relationship between static pelvis orientation and dynamic pelvis and hip joint kinematics that may influence the development of symptomatic hip morphology.