Postural control in degenerative diseases of the hip joint.

BACKGROUND: Few studies investigated the postural control in patients with hip joint impairments; in some cases, balance impairments have been found, while other researchers have seen no significant changes. The goal of this study was to characterize postural stability in patients suffering from unilateral osteoarthritis or rheumatoid arthritis in different balance tasks and to reveal potential differences between the two diseases in this respect. METHODS: Ten patients with hip osteoarthritis (mean age: 62.3years), 10 patients with rheumatoid arthritis (mean age: 55.4years) and 10 healthy control subjects (mean age: 54.3years) took part in the study. Displacement of centre of pressure was measured with a force plate in mediolateral and anteroposterior directions during two-leg standing on firm and compliant surfaces with eyes opened and closed. FINDINGS: Standing on a firm surface sway path increased significantly in the anteroposterior direction in both patient groups and in the mediolateral direction in all groups with eyes closed as compared to eyes opened condition. Standing on a compliant surface, sway paths increased significantly in both directions in all groups with eyes closed as compared to eyes opened condition; furthermore, sway paths were significantly longer with eyes closed in patients with rheumatoid arthritis in comparison with control and osteoarthritis groups. INTERPRETATION: Our data revealed that the manipulation of both visual and somatosensory information can reveal subtle impairments in balance control. Thus, this paradigm can unmask the effects of decreased proprioception due to joint capsule lesion in patients with rheumatoid arthritis.

When does mechanical plantar stimulation promote sensory re-weighing: standing on a firm or compliant surface?

The purpose of this study was to investigate the effect of different types of mechanical stimulation of the sole on standing postural stability in healthy, young adults. Fifty subjects (34 women, 16 men; mean age 23 ± 2 (mean ± SE)) stood barefoot on fixed force plates both with open and closed eyes on firm surface and then on compliant surface (foam). A modified clinical test of sensory interaction on balance protocol was employed to assess the center of gravity (COG) excursions along anteroposterior (AP) and mediolateral (ML) axes on each surface and visual condition. After the baseline measurement, a stimulation was applied with an elastic spiked layer topped to the firm and then foam surface, and the COG excursions were measured during the stimulation, and then at least 30 min after the stimulation of the spiked layer, we used 10 min of manual static and glide pressure applied to the plantar surface of both feet. Immediately after manual stimulation, static balance parameters were measured again. Results showed that after manual stimulation, the sway path with closed eyes decreased significantly on the AP and ML directions on firm surface conditions. The spiked layer caused significantly decreased sway path on firm platform in both directions, but it was ineffective on compliant surface. Our results established that the activation of plantar mechanoreceptors by 10-min manual stimulation can partially compensate subjects for the absence of visual input and the lack of accurate pressure information from the supporting surface, too.