Neuromodulation to improve gait and balance function using a sensory neuroprosthesis in people who report insensate feet - A randomized control cross-over study

Abstract

Peripheral neuropathy may cause loss of sensory information from plantar cutaneous mechanoreceptors that is important for balance control and falls management. The current study investigated short-term effects of using Walkasins, an external lower-limb sensory neuroprosthesis, on clinical outcomes of balance and gait in persons who reported peripheral neuropathy and balance problems. The device replaces lost plantar sensation with tactile balance information that modulates cutaneous mechanoreceptors above the ankle where sensation is intact. Thirty-one male community-dwelling Veterans, 56-84 years old with insensate feet and balance problems participated. Initial Functional Gait Assessment, gait speed, and 4-Stage Balance Test outcomes were assessed. After initial assessment, subjects were randomly assigned to either wearing Walkasins turned ON, or OFF, and outcomes were re-assessed following a set of standardized balance exercises. Following a one-hour rest and washout period, treatments were crossed-over between groups and a third outcomes assessment was performed. Before cross-over, 10 of 15 subjects in the ON-then-OFF group improved their Functional Gait Assessment score by at least four points, the Minimal Clinically Important Difference, compared to 5 of 16 in the OFF-then-ON group. After cross-over, 7 of 16 subjects in the OFF-then-ON group improved by at least four points versus 2 of 15 in the ON-then-OFF group. ON treatment was associated with a Functional Gait Assessment improvement of 4.4 ± 3.7 points versus 1.5 ± 1.2 for the OFF treatment (p<0.01). Overall, Functional Gait Assessment scores changed from 15.2 ± 4.8 at initial assessment to 21.1 ± 5.2 after final assessment (p<0.001). At the end of the two treatment sessions, 16 of the 31 individuals had improved their Functional Gait Assessment score beyond 23, indicating normal fall-risk status. Future studies should investigate long-term benefits of the device to reduce fall risk and actual falls in patients with peripheral neuropathy and balance problems.

Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: LIEO is co-inventor of the Walkasins technology and co-founder of RxFunction, Inc., the medical device startup that is commercializing Walkasins. LIEO is currently employed as CTO of the company, is a shareholder in the company, and a member of the Board of Directors. Patents that list LIEO as a co-inventor of the Walkasins technology are owned by RxFunction, Inc. These patents include: United States Patent 8,974,402. Issued March 10, 2015: LIEO; United States Patent 9,289,174. Issued March 22, 2016: LIEO; United States Patent 9,995,904. Issued May 1, 2018: LIEO. In addition to NIH funding, RxFunction, Inc. provided some commercial funding for this study because the senior author (LIEO) was employed as CTO of RxFunction, Inc. during the time of this study, which paid for a portion of his effort. However, this relationship does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1. CONSORT flow chart of the study.

Fig 2

The two components of the Walkasins device, the foot pad and leg unit (left), as worn on the medial side of the leg with foot pad inserted in the shoe and leg unit wrapped around the leg above the malleolus (right).

Fig 3. Outline of assessments and treatments for the ON-then-OFF and OFF-then-ON groups.

Colors illustrate how data was pooled for analysis (see Statistical analysis).

Fig 4. Consecutive changes in FGA scores for the ON-then-OFF and the OFF-then-ON groups.