Postural sway at ground and bevel levels in subjects with spina bifida occulta

Abstract

To assess whether the postural function is impaired by comparing the performances in upright standing at ground and bevel levels in adult subjects with spina bifida occulta (SBO). Eighty subjects with SBO (38 with minor type and 42 with major type) and 35 healthy control subjects participated in the study. All participants performed ten tests while standing upright on a platform at ground level (0 degrees, baseline) and on a beveled surface (with their feet in dorsiflexion and plantarflexion at 10 degrees and 20 degrees). Tests were done with their eyes open and closed. The postural sway was examined using a force platform (CATSYS, Danish) that records sway intensity and velocity. Sway intensity and sway velocity were universally associated with group, degree of bevel, open- or closed-eyes condition, and dorsiflexion or plantarflexion after adjusting for age and gender. With respect to sway intensity, the differences of minor or major SBO group were significantly decreased at different bevel degrees when compared with control groups, whereas the differences between minor and major SBO were significant differences at 10 degrees and 20 degrees. With respect to sway velocity, the differences of major SBO group were significantly decreased at different bevel degrees when compared with minor SBO and control groups, whereas the difference in minor SBO was only significant at 0 degrees when compared with control. Group differences (minor SBO vs. control, major SBO vs. control) showed a significant decrease in sway velocity when comparing at 10 degrees than at 0 degrees and at 20 degrees than at 0 degrees. In all subjects with SBO, the sway intensity/velocity values obtained with open eyes and with plantarflexion had lower values, when compared with values obtained with closed eyes and with dorsiflexion. This study supports the hypothesis that SBO impairs control of postural sway in both the resting upright and stressful postures. Our results imply that the larger the bone defect at the lumbosacral midline, the more the group differences in different stressful conditions. Both velocity and intensity were able to reflect the function of the postural sway from our results. This is the first report to add the bevel degree and foot position, as well as visual input as being the part of the study in investigating the postural sway.

Fig. 1

Four patterns of minor SBO. Type 1 is minimal defect in L5 (a) or S1 (b). Type 2 is cross-over of overlapping laminae in L5 (c) or S1 (d). Type 3 is a symmetric, wide midline defect in L5-S1 (e) or a narrow defect in L5-S1 (f). Type 4 is an asymmetric midline defect in S1 (g, h)

Fig. 2

Various patterns of major SBO involving the entire sacrum (a–d). Please note that surgical metallic clips show in the right lower quadrant of abdomen after previous appendicitis in a. Bony defect extends up to L5 in b

Fig. 3

Sway intensities of the study groups at different bevel degrees of the platform

Fig. 4

Sway velocities of the study groups at different bevel degrees of the platform