The Relationship between Postural Deformation and Standing Balance in Elderly Person.

Falling due to unstable standing balance is considered to be the main cause of bone fractures, which lead elderly persons to becoming bedridden. Thus, the standing balance of elderly persons is being given increasingly greater attention. On the other hand, postural deformation caused by deformation in the spine and lower leg joints is considered to have an effect on standing balance. The objective of this study is to clarify the effect of postural deformation on the following three categories of standing balance; 1) the ability to immobilize Center of Gravity (COG) in standing statically, 2) the ability to control COG during movement and 3) the postural response induced by postural sway. Fifty elderly persons (age:77.7 ± 6.4 years old, fifty females) participated in this study. Postural deformation was measured using a Spinal Mouse, a device for non-invasive measurement of spinal curvature and photographic image in sagittal plane. In line with to Nakata's classification of postural deformation, subjects were classified by extension type, S-character deformation type, flexion type, hands on the knee type and normal group. In order to assess the ability to immobilize COG in static standing, Center of Pressure (COP) in static standing was measured for 30 sec. In order to assess the ability to control COG during movement, functional reach, maximal length of stride and the period of 10 m gait were measured. Postural response was induced by fore-aft perturbation of the platform on which the subjects stood. Postural responses were assessed by measuring both COP, and electromyography (EMG) of muscles in the lower legs. There was little significant difference among the five groups concerning postural deformation in every measured item, neither in the ability to immobilize COP in static standing, nor in the postural response induced by postural sway. However, the results of measured items concerning the ability to control COG during movement were significantly worse in flexion type and hands on the knee type compared with the normal group. It was suggested that postural deformation in elderly persons effects exclusively on the ability to control COG during movement in standing balance.