March 2011

Socks: Getting in shape with new technologies

Socks are often an afterthought for patients with diabetes, but they shouldn’t be. Advances in materials science and new twists on old favorites mean that modern socks conform to feet without the bunching, chafing, slipping, and irritation of the past. Some even promote healing.

By Shalmali Pal

Socks have come a long way since the days of the long white tube with the colored bands around the top. A visit to any sporting goods store will offer a rock climbing wall’s worth of “performance socks,” tricked out with high-tech properties such as moisture wicking, temperature control, and arch support.

No doubt that these sock manufacturers have taken more than a few cues from diabetic socks, which have always combined fibers to maximize support, cushioning, and comfort. But do diabetic socks offer advantages to patients beyond these performance socks? Yes and no, according to the experts. Proper fit and sizing play a big part in ensuring that diabetic socks do their job.

Materials

One hundred percent cotton or wool socks have been criticized for not maintaining the sock’s shape on the foot, which can be problematic for diabetic patients on two fronts. The increased friction between the skin and the fibers can lead to ulcerations. In addition, 100% cotton or wool socks may start out quite tight, possibly reducing circulation in patients who already have compromised blood flow. As the socks are worn over time, the fibers loosen, resulting in a sock that slides between the foot and the shoe, again leaving diabetic patients vulnerable to shear, blisters, and potential ulcerations.

On the other hand, purely synthetic socks may not allow sweat to evaporate properly; sweaty feet can lead to fungal infections, which in and of itself is more complicated in a patient with diabetes than an otherwise healthy subject and can also be another gateway to ulceration. Synthetics blended with natural fibers would seem to be the best bet, offering support and—most importantly—breathing room, according to Marybeth Crane, MS, DPM, FACFAS, CWS, managing partner of Foot and Ankle Associates of North Texas in Grapevine.

“I’m not one that really likes totally cotton socks,” she said. “I find that socks with a little bit of Lycra in them are better. They also offer some compression to address swelling.”

Crane also advocates seamless socks because seams, constantly rubbing against the skin, may cause blisters, calluses, or ulcerations. For a patient with neuropathy, a skin irritation caused by the seam will not be felt immediately, increasing the risk of calluses and other pre-ulcerative conditions.

Moisture wicking can be achieved with a variety of materials: Wool, synthetics, cotton, silk, and renewable materials. Each has its pros and cons.

The biggest advantage of wool, and merino wool in particular, is that it is thermostatic so that feet stay comfortable in a range of temperatures. Wool also can absorb 30% of its own weight in water so feet are more likely to stay dry. Cushioning is another benefit, because diabetic patients have an increased risk for pressure ulcers and because focused areas of high plantar pressure are most likely to become sites of ulceration.  On the downside, wool dries out slowly, and wool socks generally carry a higher price-tag than other materials. Both factors could prove problematic for a diabetic patient who cannot afford multiple pairs of socks.

Synthetics, such as nylon and Lycra spandex, help socks retain their shape. Some synthetics may provide arch support, which can help lateralize plantar pressures and provide a bit of extra stability for diabetic patients who have problems with balance. Socks with polypropylene, polyester, or acrylic fibers will offer moisture wicking. Synthetic socks are durable but may be unsuitable for warmer climates. In addition, the socks’ insulation properties may be reduced if the socks get too wet.

Silk is a natural insulator that is often blended with wool for extra softness. The lightweight material offers reliable wicking and a smooth texture; however, it is less durable than other materials. This is important not only with regard to the cost and inconvenience of replacing socks, but also because areas of wear in a sock’s fabric fail to protect the diabetic foot and leave skin vulnerable. In addition, the very “silkiness” of a silk-based material could cause the foot to slip within the shoe, leading to abnormal skin shear and friction-induced skin issues.

A full cotton sock is not advisable for the diabetic foot. The material is easily saturated with sweat and dries slowly, both of which leave the foot vulnerable to blisters. Cotton is less expensive than other materials and, when blended in small quantities with synthetics, it can offer softness.

Eco-friendly materials, such as bamboo, corn-based polylactic acid (PLA), hemp, and charcoal, offer moisture wicking and odor control properties. Combining these materials with synthetic fabrics ups their durability.

Finally, socks made of fabrics embedded with copper, silver, or charcoal fibers offer protection against bacteria. Patients with diabetes are less resistant than healthy individuals to infection, which can lead to complications such as cellulitis (diffuse inflammation of the connective tissue) or osteomyelitis (bone infection, which almost always occurs in the presence of an ulcer). However, a sock billed as resisting bacterial growth does not automatically reduce the chance of infections on the surface of the foot, nor will this type of fabric necessarily protect an open wound from becoming infected. Visual inspection of the feet, along with daily washing, is still needed to avoid infection.

Socks come in sizes

While it’s obvious to patients with diabetes that their shoes come in sizes, the same cannot always be said for socks.

“A lot of patients don’t realize that their socks need to be the correct size,” Crane said. “If the sock is too tight, it can cause ingrown toenails, it can cause problem with compression in between the toes, it can cause ulceration between the toes.”

Crane said she advices her patients with diabetes to “size up” when it comes to socks.

“For instance, I wear a size 6-6.5 (in shoes) and most size small socks go to 6. I’ll go to a medium sock instead of a small because they will shrink once they are washed,” she said.

Socks that are too tight can reduce flow, which is particularly problematic in patients whose diabetes is complicated by vascular disorders. Poor blood flow impairs healing of existing ulcers and other wounds; it can exacerbate loss of sensation in neuropathic patients, increasing the risk of neuropathic ulcers; and it can also increase the risk of ischemic ulcers, which are even more difficult to heal. However, socks that are too big can wrinkle or bunch inside the shoe, putting excess pressure on the feet. For patients with neuropathy, a bunched sock can easily lead to blisters or ulcerations.

But as with shoes, neuropathic patients often need a sock to feel snug against their leg. A sock with binding elastic at the top may feel right to these patients, but can negatively impact blood flow.

If possible, socks and shoes should be fit simultaneously, Crane added.

“One of my pet peeves is that the socks and shoes are not fit at the same time,” she said. “I have a patient who has a beautiful pair of diabetic shoes, but she wears them with pantyhose that she buys at the drug store. The hose have a seam in them and that causes an ulceration on the tip of her toe.”

Another argument for fitting shoes and socks simultaneously is that once a sock size has been determined, the shoe size may change. For instance, a neuropathic patient who is prescribed a therapeutic sock with silicone padding to reduce plantar pressure may have to go with a shoe that is a half-size larger or convert to extra-depth shoes.

OTS socks

Crane pointed out that socks are not covered under the Therapeutic Shoe Bill (see HEADLINE, PAGE XX) so they are an out-of-pocket expense for the patient.

“Good socks are expensive,” she said. “You can’t buy a good pair of socks for $4. You are looking at as much as $20.”

As a result, off-the-shelf (OTS) socks are not always out of the question.

“In terms of the OTS, performance socks, I like the ones that have a bit of Lycra and a bit of either DryWeave or CoolMax to wick the sweat away from the foot. That’s necessary whether the person is a diabetic or not,” she said.

But these performance socks don’t necessarily offer the kind of support that a diabetic foot requires, pointed out Roy H. Lidtke DPM, CPed, FACFAOM, associate professor of podiatric medicine and surgery at Des Moines University and director of the Center for Clinical Biomechanics at

St. Luke’s Hospital, Cedar Rapids, IA. Socks made especially for patients with diabetes provide that support, along with added benefits.

“They offer extra padding and compression that can produce a form of neuromuscular feedback,” Lidtke said. “An example would be when you wear a pair of padded socks with areas of elastic compression and you feel a tightness around your arch. This provides greater proprioceptive feedback on the position and neuromuscular control of the foot.”

Diabetes is often complicated by a loss of postural control, which research suggests is a product of more than just the loss of sensation that accompanies neuropathy. Any intervention that can improve proprioception could potentially also help to improve postural control and, in turn, reduce patients’ risk of falling.

Shedding light on neuropathic pain

Advances in materials technology have seen the introduction of socks with optically modified properties.

Both near infrared light and far infrared light have shown efficacy in addressing diabetic foot problems by influencing the transmission of electromagnetic energy into the underlying tissue and skin. When incorporated into socks, near and far infrared light are credited with improving blood flow, delivering more oxygen to the tissues, and reducing swelling.

A recent study done at the University of California, Irvine looked at the effect of polyethylene terephthalate fiber socks on foot pain in patients with diabetic neuropathy and other disorders. In this double-blinded, randomized trial, 55 patients (29 with diabetic neuropathy) wore socks made from polyethylene terephthalate (PET) incorporating optically active particles (Celliant). The latter scatters and reflects visible light and near infrared light, according to the study authors.

Overall, patients reported a certain level of pain reduction. In the neuropathic patients, there was some some pain reduction but it was not as significant as it was in the patients with other foot disorders. The authors postulated that in the neuropathic foot, only a portion of the diseased neuron fibers are in close proximity to the sock. The findings were published in April 2009 by the online journal BMC Complementary and Alternative Medicine.

Far infrared and negative ion technology, which also can be incorporated in sock fibers, has been shown to reduce some of the foot discomfort associated with neuropathy. Although no studies of far-infrared socks have been published in the medical literature to date, a recent randomized clinical trial did evaluate the effects of photon stimulation with far infrared light on pain intensity and pain relief in patients with diabetic peripheral neuropathy.

Patients who underwent a series of photon therapy treatments reported significant decreases in the intensity and quality of their pain, with a 30% to 50% reduction in pain immediately following treatment, compared to those who received a placebo treatment. The findings were published in the January 2010 issue of the Journal of Pain and Symptom Management.

Sponsored by an educational grant from Dr. Comfort

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One Response to Socks: Getting in shape with new technologies

  1. Toyin Atoro-Odueyungbo PT DPT MCSP says:

    Just a feedback from a handful of diabetic patients who had purchased these socks. We had mailed out educational materials including information from this article, and got excellent feedback.
    Thank you to LER for making Diabetic condition and foot-care a focus in that publication.

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