Global postural alignment parameters have been shown to be major determinants of quality of life [1Schwab F. Spine 2012 ;

Cliquez ici pour aller à la section Références]. Gait is an essential task of functionality during daily living activities. It is still unknown how global postural alignment can influence gait. The aim was to investigate how global postural alignment can influence gait in asymptomatic subjects.

Overall, 145 asymptomatic subjects (age: 29.2±11 years [18–59], 70F) underwent 3D gait analysis followed by full body biplanar X-rays. Kinematics of lower limb segments (pelvis, hip, knee, ankle and foot) were extracted in the 3 planes during the gait cycle. Full body 3D reconstructions were obtained from the biplanar X-rays and global postural alignment was evaluated by calculating: sagittal vertical axis (SVA), center of the auditory meatus plumbline to the hip axis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic parameters (PI, PT, SS). Agglomerative hierarchical clustering (AHC) was performed on each postural parameter to classify subjects into homogeneous groups. Differences in gait parameters between groups were evaluated using ANCOVA while adjusting for demographic confounding factors (age, weight, height and sex).

The most discriminant postural parameter in gait kinematics was the SVA. AHC differentiated 3 groups of SVA: Gr1: <−16mm, n=28, Gr2: [−16,10] mm, n=62, and Gr3: >10mm, n=55. Weight, height and sex were statistically different between groups (Gr1 vs. Gr3: 68±16 vs. 77±13kg, 167, n10 vs. 173±10cm, 39F/23M vs. 6F/22M, p<0.05). After correcting for confounding factors, Gr3 had a larger hip external rotation during gait (15 vs. 13° in Gr1), higher knee flexion during loading response at the beginning of the gait cycle (18 vs. 14° in Gr1), a delayed knee extension instant during the stance phase (39 vs. 35% of gait cycle in Gr1), a smaller external foot progression angle (7 vs. 10° in Gr1) and a larger step length (68 vs. 65cm in Gr1).

This is the first study demonstrating the influence of postural alignment parameters on gait. While interindividual variations of TK and LL were not shown to impact gait, subjects with elevated SVA had their general gait modified even after correcting for confounding factors: higher duration with larger knee flexion during shock absorption phase at the beginning of gait cycle. While these results were shown in asymptomatic subjects with high SVA (>10cm), higher SVA in subjects with spinal deformities could be a cause for more altered gait kinematics.