Spinal segments do not move together predictably during daily activities

Abstract

Background: Considering the thoracic, lumbar spine or whole spine as rigid segments has been the norm until recent studies highlighted the importance of more detailed modelling. A better understanding of the requirement for spine multi-segmental analysis could guide planning of future studies and avoid missing clinically-relevant information.

Research question: This study aims to assess the correlation between adjacent spine segments movement thereby evaluating segmental redundancy in both healthy and participants with low back pain (LBP).

Methods: A 3D motion capture system tracked the movement of upper and lower thoracic and lumbar spine segments in twenty healthy and twenty participants with LBP. Tasks performed included walking, sit-to-stand and lifting, repeated 3 times. 3D angular kinematics were calculated for each spine segment. Segmental redundancy was evaluated through cross-correlation (R_xy) analysis of kinematics time series and correlation of range of motion (R_ROM) of adjacent spine segments.

Results: The upper/lower lumbar pairing showed weak correlations in the LBP group for all tasks and anatomical planes (R_xyrange:0.02-0.36) but moderate and strong correlations during walking (R_xy _frontalplane:0.4) and lifting (R_xy _sagittalplane:0.64) in the healthy group. The lower thoracic/upper lumbar pairing had weak correlations for both groups during lifting and sit-to-stand in the frontal plane and for walking (R_xy:0.01) in the sagittal plane only. The upper/lower thoracic pairing had moderate correlations during sit-to-stand in sagittal and transverse plane in patients with LBP (R_xy _sagittalplane:0.41; R_xy _transverse plane:-0.42) but weak in healthy (R_xy _sagittalplane:0.23; R_xy _transverseplane:-0.34); the contrary was observed during lifting. The majority of R_ROM values (55/72) demonstrated weak correlations.

Significance: The results suggest that multi-segmental analysis of the spine is necessary if spine movement characteristics are to be fully understood. We cannot establish a priori where redundancy occurs based on healthy data, therefore extra consideration should be made when planning studies with pathological cohorts.

Keywords: Cross-correlation; Kinematics; Low back pain; Motion analysis; Multi-segment.

Fig. 1

Schematic of marker placement and spine anatomical frames of reference (left side); Joint coordinate system axes of rotation for each spine segment considered (right side).

Fig. 2

Detection of picking and lowering phase cycles based on T1 vertical displacement and velocity. Coloured triangles show the beginning and end of each phase.

Fig. 3

Detection of STS cycle based on the right PSIS vertical displacement and velocity. Coloured triangles show the beginning (blue) and end (red) of STS phase.

Fig. 4

ROM mean (±standard deviation) of thoracic and lumbar spine segments in the 3 anatomical planes for all tasks analysed for people with (grey bars) and without LBP (light grey bars).