SmartSox: A smart textile to prevent diabetic foot amputation
Authors: Najafi Bijan 
Published: November 2013

Background: People with diabetes are at risk of developing foot ulcers (DFUs), which accounts for significant morbidity and mortality. Damage caused from repeated foot loading and temperature changes during walking may go undetected by patients due to loss of lower-extremity sensations (peripheral neuropathy). Clinical assessment on the other hand needs considerable time. Therefore, a feasible assessment of pressure and temperature is vital to measure pre-ulcerative inflammation and predict DFUs. Current study is aimed to validate effectiveness of an innovative smart textile based on fiber optics which allows measuring simultaneously plantar pressure, plantar temperature, and lower extremity joint angles. Methods: The proposed technology is based on optical fiber glass that propagates of light. Multiple sensors were juxtaposed on the length of the fiber which was integrated in a comfortable sock -SmartSox (Novinoor LLC, IL, USA) - Figure 1. Based on changes in wavelength of light, mechanical changes in environment including changes in temperature, pressure and joint angles are measured. The sensors were integrated in anatomical regions of interest including heel, mid-foot, 1st and 5th metatarsal heads, and under and over big toe. The later sensor allows measuring hallux range of motion in addition to temperature and pressure. To validate the accuracy of the designed prototype, 21 volunteers diagnosed with diabetes were recruited. Subjects were asked to walk a predetermined route of 200 steps in their normal or prescribed shoes. Plantar foot thermal images were taken by a thermal camera system twice: once at baseline after a five-minute temperature acclimation period and once after each walking trial. To determine the number of steps taken, subjects were asked to wear a gait analyzer system (LEGSys™, Biosensics LLC, MA, USA) in addition to SmartSox. To validate the accuracy of plantar pressure, a computerized pressure insole, F-scan (TekScan® Inc, MA, USA) was used as a gold standard. Results: Twenty-one patients with diabetes were recruited (Age: 57.8±7.9 years, BMI: 31.6±8.0 kg/m2, VPT: 26.8±15 volt, 68% diagnosed with peripheral neuropathy). All subjects perceived the SmartSox as comfortable and no problems were observed during walking assessment. Some fibers were however broken during wearing the socks in particular for patients who worn removable cast walker. A significant correlation was observed between the pressure profile measured by SmartSox and F-Scan under different anatomical regions of interest (r>0.6, p<0.05). A similar agreement between SmartSox and thermal camera was observed for changes in plantar temperature during walking. Conclusions: This study demonstrates the proofs of concept of an innovative smart textile for assessing simultaneously the key parameters associated with risk of foot ulcer in patients with diabetes. Fragility of the current prototype is considered as one of its major weakness for routine clinical assessment and thus further improvement in design of fiber and sock is needed. Additional study is required to address whether the measured parameters can be used to predict and better management of diabetic foot ulcer.