Effect of optically modified polyethylene terephthalate fiber socks on chronic foot pain

BACKGROUND Increasing experimental and clinical evidence suggests that illumination of the skin with relatively low intensity light may lead to therapeutic results such as reduced pain or improved wound healing. The goal of this study was to evaluate prospectively whether socks made from polyethylene terephthalate (PET) incorporating optically active particles (Celliant) ameliorates chronic foot pain resulting from diabetic neuropathy or other disorders. Such optically modified fiber is thought to modify the illumination of the skin in the visible and infrared portions of the spectrum, and consequently reduce pain. METHODS A double-blind, randomized trial with 55 subjects (38 men, 17 women) enrolled (average age 59.7 +/- 11.9 years), 26 with diabetic neuropathy and 29 with other pain etiologies. Subjects twice completed the Visual Analogue Scale (VAS), Brief Pain Inventory (BPI), McGill Pain Questionnaire (MPQ), and SF-36 a week apart (W(1+2)) before receiving either control or Celliant socks. The same questionnaires were answered again one and two weeks (W(3+4)) later. The questionnaires provided nine scores for analyzing pain reduction: one VAS score, two BPI scores, five MPQ scores, and the bodily pain score on the SF-36. Mean W(1+2) and W(3+4) scores were compared to measure pain reduction. RESULTS More pain reduction was reported by Celliant subjects for 8 of the 9 pain questions employed, with a significant (p = 0.043) difference between controls and Celliant for McGill question III. In neuropathic subjects, Celliant caused more pain reduction in 6 of the 9 questions, but not significantly. In non-neuropathic subjects 8 of 9 questions showed more pain reduction with the Celliant socks. CONCLUSION Socks with optically modified PET (Celliant) appear to have a beneficial impact on chronic foot pain. The mechanism could be related to the effects seen with illumination of tissues with visible and infrared light. TRIAL REGISTRATION ClinicalTrials.gov NCT00458497.