The Effects of Random Vibrations on the Vibratory Perception Threshold of the Foot and Standing Balance in People With Diabetic Neuropathy

Rationale: People with diabetes mellitus often suffer from polyneuropathy. Reduced somatosensation of the feet due to polyneuropathy is one of the major risk factors for ulceration at the plantar side of the feet and may often cause problems in balance. It has been shown that the application of a mechanical noise signal to the feet (a vibration with a random frequency) can reduce the sensation threshold and improve standing balance. However, techniques used in research so far have several problems that limit applicability in daily practice. New vibrating insoles have been developed that overcome these problems, but it is unknown if these insoles have the same effects.

Study population: Two samples of 20 consecutive patients with diabetes mellitus will be included. Patients will be included if their VPT is between 25 and 45V. Patients with a history of ulceration on MTP, halllux or heel region will be included in the first sample group. In the second sample group patients with no history of ulceration will be included. Patients with an ulceration or (a history of) amputation will be excluded in both groups.

Intervention: First, participants will be standing on vibrating insoles placed on a platform for the measurement of VPT. Secondly, participants will be standing on a force platform while wearing standardized shoes in which vibrating insoles are placed. The insoles are either turned on (i.e. random vibrations applied) or off (i.e. no random vibrations applied).

Main study parameters: Vibration perception threshold and centre of pressure displacements.