Dynamical Analysis of Standing Balance Control on Sloped Surfaces in Individuals with Lumbar Disc Herniation

Abstract

The changes of balance control mechanism caused by lumbar disc herniation (LDH) has not been well understood. This study aimed to investigate the effects of LDH on the balance control during standing on sloped surfaces. Ten patients with LDH and 10 gender- and age-matched healthy subjects were instructed to stand quietly on a sloped surface at -5°, 0° or +5°, respectively. The trajectories of the center of pressure (COP) of each individual limb and the full-body were recorded. Cross recurrence quantification analysis (CRQA) was applied to assess the coordination of COP components at the anterior-posterior and medial-lateral directions. The patients with LDH presented magnified inter-limb load asymmetry and had more deterministic components in the COP coordination of the less-affected limb and the full-body than the healthy subjects. The LDH led to decreased dynamical degree of freedom and less flexibility in bidirectional controlling the center of mass simultaneously. The effects of sensorimotor deficits due to LDH could be more obviously exhibited as standing on a declined rather than an inclined surface. This study shed light on the effects of LDH on standing balance control and may facilitate to develop novel strategies for evaluation of LDH.

Figure 1

The schematic diagram of the experiment set-up and foot plantar pressure distributions from a representative patient with LDH. (a) Declined surface at −5°; (b) horizontal surface at 0°; (c) inclined surface at +5°; (d), (e) and (f) are foot plantar pressure distributions corresponding to (a), (b), (c), respectively.

Figure 2

The mean and standard deviations of the time series of the limb load asymmetry (LLA) for all the patients with LDH and the healthy subjects (HC). (a) Declined surface at −5°; (b) horizontal surface at 0°; (c) inclined surface at +5°.

Figure 3

The full-body COP trajectories and the cross recurrence plots (CRP) during standing on a horizontal surface. (a) The COP components of the anterior-posterior (AP) direction and the medial-lateral (ML) directions from a representative patient with LDH; (b) The COP components of the AP and the ML directions from a healthy subject; (c) The CRP of (a); (d) The CRP of (b).

Figure 4

Statistical results of the CRQA analysis for the less- and more-affected limbs. ^*Significant difference between the LDH and HC groups (p < 0.05); ^#significant difference across the slope angles (p < 0.05).

Figure 5

Statistical results of CRQA analysis of the full-body COP. ^*Significant difference between the LDH and HC groups (p < 0.05); ^#significant difference across the slope angles (p < 0.05).