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Aging Clinical and Experimental Research
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Can tactile plantar stimulation improve postural control of persons with superficial plantar sensory deficit? Laurence Bernard-Demanze1, Nicolas Vuillerme2, Myriam Ferry1 and Loetitia Berger1 1Laboratoire
de Modélisation des Activités Sportives, Domaine Universitaire de Savoie-Technolac, Le Bourget du Lac cedex, 2Laboratoire TIMC-IMAG UMR UJF CNRS 5525, Faculté de Médecine de Grenoble, La Tronche cedex, France
ABSTRACT. Background and aims: Complex interactions between visual, vestibular and somatosensory information and the cerebellar system are involved in the maintenance of upright posture. Previous studies have shown that normal aging and pathologies may lead to deterioration of the control of upright standing posture. Methods: In order to investigate postural control during quiet standing in the elderly, the center of pressure (CoP) was analysed on two force platforms in three different groups. The first group was composed of 13 healthy older adults (O), the second consisted of 9 older adults with plantar sole deficit (OD), and the third (control) group was composed of 8 young healthy subjects. All subjects were tested with eyes closed, before and after tactile plantar stimulation lasting ten minutes. Center of pressure displacements were analyzed in terms of sway area, mean velocity, and mean root mean square (RMS) along both mediolateral and antero-posterior axes. Results: Results showed that, before tactile plantar stimulation, the sway area and mean RMS were greater in O and OD subjects compared with Y ones. After tactile plantar stimulation, a decrease in the mean RMS was observed in OD subjects, this effect being significant only for the medio-lateral axis. Conclusions: These results suggest that application of tactile plantar stimulation may compensate a loss of superficial plantar sensitivity. (Aging Clin Exp Res 2009; 21: ###-###) ©2009,
Editrice Kurtis
INTRODUCTION It has been well established that distal sensory neuropathy under the feet impairs postural control (1). More precisely, the sway area is larger and the estimated con-
duction velocity of group II afferent fibers is lower in neuropathic patients compared with healthy subjects (2). The loss of sensory perception secondary to diabetic distal symmetrical sensory neuropathy leads to postural instability: postural sway and sway velocity are increased in diabetic patients with sensory cutaneous deficit in the foot (3). The deficit is even more important when visual or vestibular cues are absent or degraded (4). Similarly, a decline in visual perception, vestibular function and somatosensory sense is observed in older adults (5), who increase their postural sway. Nevertheless, reduced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy may be significantly improved with input of mechanical noise (6). Previous studies (7, 8) point out that experimental manipulations of tactile plantar soles affect the postural control of healthy subjects during quiet standing. For instance, reduction of cutaneous information, either by cooling or placing a cuff on the leg, is associated with greater foot center of pressure (CoP) displacements (7). A local anesthetic into the entire weight-bearing surface of the foot soles impairs postural stability (9). Conversely, standing on a shotgun ball platform results in a decrease in the sway area covered by the foot center of pressure displacements (8). Moreover, applying vibration to the plantar soles also improves postural control in young and older adults (10). From a therapeutic point of view, the application of tactile plantar stimulation may modify postural control. Various experimental protocols have been used to analyze plantar sole stimulation effects, suggesting that tactile plantar stimulation may be important in improving the role of cutaneous afferent inputs in the standing posture (11). A study by Hsiao-Wecksler et al. (12) has suggested that, for a given individual, the postural control system may use the same control mechanisms during quiet
Key words: Aging, center of foot pressure, plantar sensory deficit, postural sway, tactile plantar stimulation. Correspondence: Laurence Bernard, MD, Laboratoire LMAS, Bâtiment Beaufortain, Campus scientifique, 73376 Le Bourget du Lac, France. E-mail:
[email protected] Received November 15, 2007; accepted in revised form July 2, 2008.
Aging Clin Exp Res, Vol. 21, No. 1 1
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stance and mild-perturbation conditions, regardless of age. Also, the aim of the present study was to examine the role of tactile plantar stimulation among older participants with or without superficial plantar sensory deficit on their postural control during quiet standing. It was hypothesized that plantar tactile stimulation would decrease postural sway during quiet standing. MATERIALS AND METHODS Subjects and clinical characteristics Thirty subjects volunteered for participation in this study, in accordance with the Helsinki Convention (1983): 16 healthy adults, including 8 young participants (Y: 5 men and 3 women), 13 older subjects (O: 8 men, 5 women) and 9 older subjects with superficial plantar sensory deficit (OD: 2 men, 7 women). Older subjects with superficial plantar sensory deficit suffered from peripheral neuropathy, which was asymptomatic. All subjects gave their informed consent before their participations in this study. We excluded volunteers who reported the following various disabilities: previous physical, neurological disorders and regular medication that might influence their balance and/or cognitive performance, no ability to ambulate independently, being wheelchair-bound, a history of falls in the previous 12 months, and living in an institution. Semmes-Weinstein monofilament test Cutaneous sensitivity was assessed by the Semmes-Weinstein monofilament test (SW) on plantar foot soles and various foot sites in all groups. Test sites were prearranged to examine plantar peripheral sensitivity throughout both feet before tactile plantar stimulation. The monofilament test measured the patient’s ability to sense a point of pressure. There were six types of monofilament: 2.83, 3.61, 4.31, 4.56, 5.07 and 6.65 (0.07, 0.2, 2, 4, 10 and >75g force respectively). While subjects were unable to observe their feet in a sitting position, we tested the first, third and fifth toes, the first third and fifth metatarsal heads, the plantar foot sole, and the heel, in random order. The SW monofilament was pressed perpendicular to the test site with enough pressure to bend the monofila-
ment for 1 s (13). Subjects were asked to answer “Yes or No”, when they felt or did not feel the press of the monofilament, respectively. Monofilament test scores ranked the older adults in the O or OD groups. Cutaneous sensitivity decreased significantly with increasing size of monofilament. So large monofilaments (4.56, 5.07) discriminated a loss of superficial tactile sensitivity in OD subjects. The inability to sense the 5.07/10-g monofilament was considered as an independent predictor of higher risk of foot ulceration (14). The OD group had the lowest level of sensitivity in the plantar foot sole (right foot: 4.56±1.3; left foot: 5.07±1.3) (p
