PURPOSE: Postural stability, a contributor to functional mobility, can be significantly affected by aging. Aging is often accompanied by other comorbidities such as peripheral neuropathy. Since neuropathy degrades sensory function in the feet, the compensatory mechanisms utilized to maintain postural steadiness could be affected. Vision is a major contributor in the mix of afferent information integrated during postural tasks. Thus, neuropathy-related sensory impairment may alter the importance of visual feedback for these patients.
METHODS: Twelve young (Y, 23±3 yrs), 13 healthy elderly (HE, 73±8 yrs), 9 elderly fallers (EF, 77±7 yrs), and 32 peripheral neuropathy patients (PN, 72±8 yrs) underwent an assessment of their maximum voluntary contraction (MVC) force and postural control during quiet standing. The subjects performed 60s trials with eyes open (EO) and closed (EC). Anterior/posterior (AP) sway (APsway), path length (PL), and elliptical area (Earea) were measured on force platforms.
RESULTS: Values are pooled for the HE and EF groups. Dorsiflexor (DF) MVC force was reduced (P<0.01) in HE/EF (206±71 N) and PN (174±76 N) compared with Y (295±87 N). Plantarflexor (PF) MVC force was also reduced (P<0.01) in HE/EF (418±228 N) and PN (395±256 N) compared with Y (920±303 N). Group differences: APsway, PL, and Earea were 45%, 141%, and 130% greater (P<0.05) for PN compared with Y and 23%, 57%, 97% greater for PN compared with HE/EF. Visual conditions: Pooled across groups, APsway, PL, and Earea were 30%, 44%, and 51% greater, respectively, (P< 0.001) for the EC than the EO condition. Vision effects for groups: The PN group displayed substantially greater changes from the EO to EC condition compared with the other groups (group × visual condition interaction, P<0.001) for APsway (64% increase), PL (74% increase), and Earea (98% increase).
CONCLUSION: Peripheral neuropathy produces sensory dysfunction sufficient to significantly impair postural stability compared with age-matched older adults. When the benefit of visual feedback is removed and the reliance on cutaneous sensation and proprioception is increased, postural stability is substantially worsened for subjects with peripheral neuropathy.
Funded by the Poudre Valley Foot and Ankle Clinic and the College of Applied Human Sciences Pilot Grant Program