Abstract
Purpose and Background
Physical mechanisms underlying back pain impairment are poorly understood. Measuring movement features linked to back pain should help understand its causes and decide on best management. Previous kinematic studies have pointed to diverse features distinguishing back pain sufferers. However, the complexity of 3D kinematics means that it is difficult to choose, a priori, which variables or variable combinations are most important. This study set out to obtain a rich set of kinematic data from spinal regions and lower extremities during typical movement tasks, and analyse all of these variables simultaneously to obtain globally important distinguishing features. To this end, a novel distance metric between pairs of motion sequences was used to construct distance matrices. Analyses were carried out directly on these distance matrices.
Methods and Results
20 controls (age: 28 ± 7.6, 10 female) and 20 chronic LBP subjects (age: 41 ± 10.7, 4 female) were recruited. Kinematic data were obtained whilst subjects stood from sitting (‘STS’), picking up (‘Picking’) and lowering (‘Lowering’) a 5kg box, and walking (right (‘WalkRight’) and left sides (‘WalkLeft’)).
For each task, permutation tests for group differences were carried out, based on the pseudo-F statistic calculated from the distance matrices. A similar approach was used to identify local differences at time points and joints. Group mean motion sequences were compared using a custom OpenSim model. Significant differences were obtained for STS (pseudo-F=2.8, p=0.017), WalkRight (pseudo-F=3.27, p=0.008) and WalkLeft (pseudo-F=3.39, p=0.005).
Conclusion
Comparisons of movement tasks between groups revealed significant differences for STS and walking. Visualisation of group mean motion sequences, and local analyses assisted in the detailed understanding of these differences. This provides a visually intuitive means of studying complex motion differences between groups, without prior assumptions regarding which variables are important.
No conflicts of interest
No funding. Original study funded by Arthritis Research UK MRC (Medical Research Council) Centre for Musculoskeletal Health and Work.
