Footwear for diabetics
Robert Gajewski, Iwona Maslowska-Lipowicz and Katarzyna Lawinska
Until 1922, diabetes was a fatal disease. This is no longer the case, but many patients with diabetes must face up to a number of possible health complications. The three most important are: retinopathy, nephropathy and neuropathy.
The last of these is of particular interest here owing to its connection with the development of diabetic foot syndrome. The risk of developing diabetic foot syndrome affects up to 25% of people with diabetes1.
The most visible effect of diabetic foot syndrome is the occurrence of ulcers. There is a lifetime risk of diabetic foot ulceration for up to 34% of patients2. Relapses are common after initial healing; approximately 40% of patients relapse within a year of ulcer healing, almost 60% within three years and 65% within five years.
In extreme cases, diabetic foot syndrome can lead to Charcot’s Syndrome (sometimes called Charcot’s Foot), which is characterised by the destruction of bones and joints. The incidence of Charcot’s Syndrome in diabetes ranges from 0.1% to 8%2. In very extreme cases, this may lead to amputation. The probability of amputation in patients with diabetes is 30-40 times higher than in people without diabetes 3, 4, 5.
Nerve impulses
An important issue is the pathogenesis of the development of diabetic foot syndrome. A commonly accepted view is that the main factor leading to the development of diabetic foot syndrome is neuropathy, which is to say damage to peripheral nerves as a result of their demyelination caused by hyperglycaemia5. The longest sections of nerves, which are the nerves leading to the feet, are most exposed to destructive factors. Impaired conduction of nerve impulses limits people’s sense of touch in the feet, their ability to feel the ground and, in general, proprioception.
In this condition, the patient does not feel excessive pressure and does not control the position of the foot, which leads to overload in various areas of the foot. Incorrect flow of nerve impulses also causes inappropriate muscle tension, which additionally changes the distribution of pressure on the plantar side of the foot. As a result, overloading various areas of the foot leads to the formation of wounds and ulcers, which are difficult to heal owing to impaired functioning of the circulatory system.
Glucose levels
Prevention of complications of diabetic foot syndrome can be achieved at two levels. It is crucial to manage the patient in a way that prevents abnormal glucose levels. This is an obvious action and comes down to appropriate pharmacology and patient care, including an appropriate diet. If the patient is properly treated and disciplined, there is a good chance that abnormal glucose levels will not occur and, therefore, complications in the course of diabetes will not occur.
However, regardless of whether you manage to control your glucose levels or not, it is necessary to control and care for your lower limbs.
From passive to active
Of course, the level of control depends on many factors. The main criterion is to avoid wearing shoes that may cause abrasions and discomfort. Essential criteria to be followed include avoiding the risk of tissue damage, avoiding excessive pressure that could lead to wounds or ulcers, and redistributing pressure away from the most sensitive areas of the foot.
Good design of the sole and insole of the shoe is important for reducing high pressure on the plantar side of the foot. The use of good shoes and good insoles as a method for treating symptoms, but it is a passive method. Because the main factor in the development of diabetic foot syndrome is neuropathy, the damage to peripheral nerves, there is also a need to develop an active method, one that provides nerve protection.
This was the focus of a recent project at the Lukasiewicz Research Network - Lodz Institute of Technology in Poland. The main element of the system the research team developed are shoes that have insoles with pressure sensors.
Pulse rate
It has been observed that Low-Intensity Pulsed Ultrasound (LIPUS) and Pulsed Electromagnetic Field (PEMF) can enhance peripheral nerve regeneration. In this project, this observation became the starting point for the development of the special footwear. The insoles in the shoes generate LIPUS and PEMF at specific frequencies.
These frequencies had already been determined in vitro tests conducted on Schwann cells and neuronal cells, as well as by analysis of genes involved in pro-inflammatory processes and genes involved in the processes of growth and regeneration of peripheral nerves. The project examined the potential benefits of wearing the special shoes with insoles that generate these pulses as shown above (1).
The pulses are powered by accumulators, which are coupled with a control module mounted on the user’s belt as shown (2).
Right dimensions
The footwear developed for the project meets all the requirements for footwear for people with diabetes. These include greater width in the forefoot area, a higher toe and attachment to the foot (with laces or hook-and-loop) enabling the footwear to be adjusted to the width of the foot and to the changing width of the foot during the day. The general requirements for such footwear are large dimensions for the interior of the footwear and a good fit of the shoe upper to the foot.
Specific areas of focus in the construction of the footwear include length; the footwear should be around one centimetre longer than the foot. Also, the position of any stitching or joining of pieces should not be where the material will come into contact with the most sensitive areas of the feet.
Dimensions of the interior of the footwear must also take into account the thickness of the insole. This last parameter is particularly important in this case because the thickness of the specialist insole the project team developed is 11 millimetres.
Cable conundrum
One of the most difficult tasks the team faced was designing a method for running the cable connecting the pulse-emitters, the battery and the control system. The cable has to be thick enough to stand up to wear and movement, but at the same time, must not do anything to lessen foot comfort for the wearer. In the case of people with diabetic foot syndrome, an impaired sense of touch could leave wearers unaware of too much pressure and this could cause injuries.
The project team modified the insole and adapted the construction of the shoe to prevent this.
For the purpose of reducing plantar pressure in the area of metatarsal joint and to reduce the bending forces acting on the insole, the team decided to use a roller sole, but made sure it was not completely stiff. To make sure the insole would cause no harm to the plantar surface of the foot, it set about measuring the plantar pressure distribution pattern.
Treadmill tests
Insoles with pulse-emitters were compared to reference insoles of the same thickness made from ethylene-vinyl acetate (EVA). Ten people took part in tests on a treadmill, walking at two speeds: 2 kilometres per hour, and 3 kilometres per hour. Each person carried out the test three times in shoes with the pulse-emitting insoles, and three times with the reference insoles.
These results confirm that an insole that generates pulses at the right frequency, from the point of view of plantar pressure, is better because the maximum pressure is lower and the differences are statistically significant. Additional operational tests followed to verify in the field the performance of the whole system.
Added functionality
As well as design, materials are an important aspect of footwear for diabetics. Foot ulcers, which are very common in diabetics, are highly susceptible to infection. Skin injuries such as wounds and burns are often worsened by colonisation by the Pseudomonas aeruginosa (P. aeruginosa) bacterium, causing infections. P. aeruginosa is responsible for more than 50% of all severe burn infections and is the second most common organism isolated from chronic wounds, including diabetic ulcers, bedsores and burn wounds6.
In this context, preventing the colonisation of microorganisms in the foot or wound will result in faster healing, making a significant contribution to preventing the occurrence of infections.
Giving additional functions (antibacterial, antifungal or self-cleaning) to footwear materials can prevent infections in the lower extremities of diabetic patients or result in faster healing of already existing wounds. The team at the Lukasiewicz Research Network - Lodz Institute of Technology made modifications to various footwear materials (leather, textiles and plastics) to endow them with antibacterial, antifungal and self-cleaning functionality 7,8. To achieve this, it used commercial products and also innovative substances produced in the network’s laboratory. The methodologies used are spraying, surfacing, the sol-gel method and thin film.
The active therapeutic footwear developed in this project offers the following features that could benefit people with diabetes:
suitable construction,
appropriate materials,
LIPUS (Low intensity pulsed ultrasound ) and PEMF (Pulsed electromagnetic field therapy) emitters,
regeneration of degraded cells,
possible formal certification as footwear for diabetics.
The team’s conclusion is that the design and features of the footwear (materials, emitters and other components) mean that the footwear can be effective in the treatment of diabetic foot problems and contribute to an increase in the activity of people who have diabetic foot syndrome.
References
1. Singh Nalini, Armstrong Dawid G, Lipsky Benjamin A. 2005. ‘Preventing foot ulcers in patients with diabetes’. JAMA. 12;293(2):217-28. doi: 10.1001/jama.293.2.217.
2. Edmonds M., Manu Ch., Vas P. 2021. ‘The current burden of diabetic foot disease’. J Clin Orthop Trauma. 17: 88-93. doi: 10.1016/j.jcot.2021.01.017.
3. Lavery L A, W H van Houtum, Ashry H R, Armstrong D G, Pugh J A. 1999. ‘Diabetes-related lower-extremity amputations disproportionately affect Blacks and Mexican Americans’. 92(6): 593-9, doi: 10.1097/00007611-199906000-00008.
4. Korzon-Burakowska A. 2008. ‘Zespól stopy cukrzycowej – patogeneza i praktyczne aspekty postepowania’. Forum Medycyny Rodzinnej. 2008;2(3):234-241.
5. Siitonem O I, Niskanen L K, Laakso M, Siitonen J T, Pyörälä K. 1993. ‘Lower-extremity amputations in diabetic and nondiabetic patients. A population-based study in eastern Finland’. 16(1): 16-20. Doit: 10.2337/diacare.16.1.16.
6 Nichols, D.P. et al. (2013) Effects of azithromycin in Pseudomonas aeruginosa burn wound infection. Journal of Surgical Research, 183 (2), 767- 776.
7. Maslowska-Lipowicz, I., at al. (2023). Novel method of obtaining textile fabrics with self-cleaning and antimicrobial properties. The Journal of the Textile Institute, 114 (10), 1509-1517.
8. Maslowska-Lipowicz, I., at al. (2024). Footwear Innovation to Improve the Comfort of Use. In Lawinska K., Jablonska M.(red.), The importance of social innovations in the knowledge-based economy in the context of footwear sector solutions, Wydawnictwo Uniwersytetu Lódzkiego, Lódz 2024.
Note
This project was funded by the Ministry of Science and Higher Education of Poland as part of a programme called ‘Science for Society’. The project’s title is ‘Active therapeutic footwear dedicated to patients with diabetic foot syndrome’. The project’s grant number is: NdS 547732/2022/2022.
Authors
The authors work at the Lukasiewicz Research Network - Lodz Institute of Technology in Poland.
