Effect of flat insoles with different Shore A values on posture stability in diabetic neuropathy.

The objective of the study was to determine whether insoles with a low Shore A value (15 degrees) as prescribed for patients with a diabetic neuropathy have a negative effect on posture stability because these insoles may reduce somatosensory input under the feet. It was conducted in the Center for Rehabilitation, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands The study was observational and conducted on 30 diabetic patients (aged 37 - 82 years) with a neuropathy. Posture stability (body sway) was assessed in a shoe without insole, on a flat insole with a low Shore A value (15 degrees) and on a flat insole with a higher Shore A value (30 degrees). These assessments were done under four different conditions: (1) eyes open, no dual-task, (2) eyes closed, no dual-task, (3) eyes open, dual-task (mental arithmetic) and (4) eyes closed, dual-task. Additionally 10 healthy controls (aged 27 - 51 years) were assessed similarly. A significantly higher root-mean-square (rms) value of the anterior-posterior velocity, V(y), was found in patients compared with controls (3.4 cm/s vs. 1.2 cm/s, p < 0.05). Also a significant difference in rms value of the anterior-posterior velocity, V(y), was found between eyes open and eyes closed (1.9 cm/s vs. 2.7 cm/s, p < 0.05). No significant effects were found for insoles or dual tasks for the total group. In diabetic patients no significant effect was found of insoles on posture stability. The effect of closed eyes on posture stability was significantly larger for diabetic patients compared to controls. It was found that prescribing insoles with a low Shore A value (15 degrees), compared to insoles with a higher Shore A value (30 degrees) has no significant negative effect on posture stability in patients with a diabetic neuropathy.