Third-Degree Burn on the Neuropathic Lower Extremity in a Patient With Diabetes While Wearing a Copper–Containing Compression Sock: A Case Report

Compression socks are used in the management of venous and lymphatic diseases. A literature review reported that low levels of compression (10–30 mm Hg) are effective to manage telangiectasia after sclerotherapy and varicose veins as well as to prevent edema and deep vein thrombosis, while high levels of compression (30–40 mm Hg) are effective to heal leg ulcers and manage lymphedema.¹ A 2014 Cochrane review concluded that compression hosiery reduced rates of venous ulcer recurrence.² In addition, compression socks are increasingly used by athletes. A literature review by Stanek³ of 4 randomized crossover studies reported that 2 studies demonstrated improved performance while wearing compression socks and 1 demonstrated lower perceived muscle soreness after exercise.

Compression socks are widely available to the public and vary in lengths available, level of compression advertised, and instructions for sizing. Some compression socks include copper and are promoted as preventing odor.⁴ This claim is supported in a review stating that copper oxide is biocidal,⁵ which will eliminate the bacteria that cause odor. There are additional claims that the copper in the socks will help prevent skin infections and rejuvenate the skin.⁶ A pilot study by Zatcoff et al⁷ showed improvement or resolution of tinea pedis in 56 patients after wearing copper-oxide–impregnated socks for 40 days. A double-blind placebo-controlled study by Dykes⁸ with 60 participants showed an improvement in skin elasticity after 4 weeks in participants who wore copper-infused socks for 10 hours a day.

Peripheral neuropathy affects nearly 50% of adults with diabetes, thus putting them at risk of pain, ulcers, and amputation.⁹ Persons with diabetes may develop edema for several reasons, including congestive heart failure, kidney failure, and side effects of medications.¹⁰ The true prevalence of edema in this population is unknown; one prospective study reported peripheral edema in 38% of 314 patients with diabetic foot ulcers.¹¹ Several studies have demonstrated that compression can be used safely and effectively in persons with diabetes without impairing time to heal an ulcer or decreasing microperfusion if arterial flow is sufficient.^10,12,13 In a randomized controlled trial, Wu et al¹⁰ demonstrated success in decreasing calf and ankle circumference due to edema after using compression socks of 18 to 25 mm Hg.

Contraindications to wearing graduated compression stockings include severe peripheral arterial disease, epifascial arterial bypass, severe peripheral neuropathy or other sensory impairment, allergy to stocking material, severe cardiac insufficiency, local skin or soft tissue condition (such as recent skin graft, dermatitis, or cellulitis), and a deformity or unusual leg shape that prevents obtaining a correct fit.^14,15 A 2020 international consensus statement reports a number of adverse events that may occur due to the use of medical compression and compression socks. These events include common events (>1/100 to <1/10) such as mild skin irritation and discomfort or pain, rare events (>1/10,00 to < 1/1000) of forefoot edema, and very rare events (<1/10,000) of allergic skin reaction, bacterial and fungal infection, soft tissue damage or necrosis, nerve damage, arterial impairment, venous thromboembolism, or cardiac decompensation.¹⁵ To the author’s knowledge, the literature does not contain documented cases of an adverse event due to the use of copper- or silver-infused compression socks.

The purpose of this case study is to describe a patient with neuropathy who developed third-degree burns while wearing a copper-containing compression sock. Informed consent by the patient was obtained for the use of photographs and all health information relevant to this case.

The patient was a 68-year-old man with a left below-knee amputation who reported spending 3 hours sitting in the sun while wearing a copper-containing compression sock on the right leg on May 1, 2020. He stated that his leg “felt funny later on” and when he removed his sock, there was blistering. Two (2) days later he scheduled a telehealth visit with an urgent care physician because he was concerned about infection. The video visit failed due to technical difficulties and was performed as a telephone visit. The physician reported that the patient stated the area was red, but denied any pus, fever, or chills. The patient was instructed to use Silvadene dressings and was prescribed clindamycin prophylactically for 10 days. The physician also recommended that the patient follow up in 1 to 2 days in person with his primary care physician.

The following day the patient completed an in-person visit with his physician, who documented that the patient’s neuropathy started about one-third of the way down the lower leg. The patient was diagnosed as having partial-thickness burns to the anterior shin and dorsum of the foot, with the largest area measuring 16 cm x 6 cm and a proximal area being 7 cm in diameter. The patient was instructed to follow-up if a significant wound was present after 1 week. On June 2, the patient requested a referral to the wound clinic and was seen 10 days after receiving the referral.

The patient’s history included type 2 diabetes, congestive heart failure, coronary artery disease, stage 3 chronic kidney disease, ischemic cardiomyopathy, peripheral arterial disease, mitral regurgitation, left below-knee amputation, implantable cardioverter-defibrillator, colonization with methicillin-resistant Staphylococcus aureus in the left foot, and obesity. He quit smoking in 1975. The most recent ankle-brachial index (ABI) available was from December 2016, at which time the right ABI was falsely elevated with triphasic waveforms. The digital-brachial index was .74. An ABI was not done in the clinic because ABIs were to be performed in the institution’s Intersocietal Accreditation Commission-accredited vascular laboratory. Because the patient was seen during the COVID-19 pandemic, however, the policy at that time was to limit in-person medical visits as much as possible. Therefore, the decision was made to assess the patient’s progress over the first few visits before pursuing an ABI. The patient was making excellent progress; thus, an ABI was not pursued.

The patient reported that his most recent glycated hemoglobin result was 10% about 3 months prior to the wound clinic evaluation. This could not be confirmed because the patient received some care from a different medical system. He reported his current blood glucose readings as ranging from 80 to 220 mg/dL. His body mass index was 34.

Physical evaluation revealed 6 open wounds that were determined to be third-degree burns surrounded by areas of second-degree burn based on pictures taken by the patient on May 2, which showed necrosis in several areas. At the wound clinic evaluation, 3 of the wounds contained thick necrotic tissue, and the remaining wounds contained thick slough that ranged from loose to adherent (Figure 1). Dorsalis pedis and anterior tibialis pulses were not palpable due to wound location. The posterior tibialis pulse was not palpable due to edema. Wound treatment included sharp debridement (Figure 2) as well as applying honey gel to the remaining areas of necrosis and silver foam to areas with granulation tissue. The patient had stopped wearing the compression sock because it was difficult to get on due to the wound dressings. Gentle compression was applied using tubular compression. The patient was instructed how to perform daily dressing changes and educated about the importance of blood glucose control for healing. The wounds made excellent progress despite the patient reporting at his third visit, on July 2, 2020, that he was sometimes leaving them open to the air for 4 to 5 hours. The wounds were healing well after 5 weeks (Figure 3) when the patient was lost to follow-up.

A referral to a plastic surgeon for consideration of skin grafting was not pursued because this treatment episode occurred during the COVID-19 pandemic, when emergent surgeries only were being performed. In addition, because the wounds were not infected and were healing well, surgery was not indicated.

The author contacted the seller of the patient’s compression socks to inform them of the adverse event and received an acknowledgement as well as a statement that the information would be passed along to the manufacturer. Additionally, a report was filed with the FDA Safety Information and Adverse Event Reporting Program.

Compression socks are commonly used and widely available. Recommendations for use include decreasing swelling and improving blood flow, both of which could be useful to patients with diabetes. Some compression socks are infused with copper or silver. This is the first case report, to the author’s knowledge, to document thermal injury from metal-infused compression socks in a patient with diabetes and neuropathy.

Thermal burns in patients with diabetes have been commonly reported but the overall incidence is unknown. A retrospective study by Mun et al¹⁶ of 864 patients demonstrated that patients with diabetes are at risk of sustaining contact burns from therapeutic physical modalities, such as hot packs and heating pads. Barsun et al¹⁷ documented in a 10-year retrospective review of lower extremity burns in patients with diabetes that common causes of burns include walking on a very hot or very cold surface, soaking in hot water, warming feet near something hot, or spilling hot water. The presence of neuropathy in patients with diabetes is a strong contributing factor to the risk of thermal injury.

Although heating devices are, by their nature, an obvious source of heat, it is less apparent that one could sustain a thermal burn due to wearing socks containing a metal. Copper and silver are known to be excellent conductors of heat; of the more common metals, they are the most conductive.^18,19 In addition, they both have a low specific heat capacity, meaning that they do not hold heat for long. This requires that the heat be absorbed by something else, in this case the patient’s skin and subcutaneous tissue.²⁰

Conduction is the most significant form of heat transfer within a solid object or between solids in thermal contact.²¹ Because atoms are close together, 2 solid materials in contact will transfer heat from one to the other better than a solid in contact with a gas.²² The close contact of the compression sock with the underlying skin means that as the copper cools, the heat would be absorbed at least in part by the skin. In a literature review of the pathophysiological implications of diabetes on burns, Goutos et al²³ stated that skin dissipates heat energy through passive conduction to surrounding tissues and through increased blood flow in the affected tissues. In addition, “Studies have confirmed that diabetes is characterised by diminished heat energy transfer to the surrounding skin as well as a weaker hyperaemic response.”²³ Thus, the tissue will be less able to dissipate any accumulated heat.

Multiple studies show that when patients with diabetes sustain a burn, they are at an increased risk of complications. A retrospective cohort study by Dolp et al²⁴ demonstrated that patients with diabetes had a longer length of hospital stay per percentage surface burn area, higher morbidity rate, more wound infections, higher risk of sepsis, and higher rates of renal, respiratory, and heart failure. In addition, 63% of the 76 patients in this study were discharged from the hospital while taking escalated antidiabetic medication. In a retrospective cross-sectional survey, Momeni et al²⁵ reported that patients with diabetes had more amputations than other burn patients. Memmel et al²⁶ reported in a retrospective review that patients with diabetes who sustained burn injuries were significantly more likely to be readmitted to the hospital. Patients who have diabetes are at increased risk of difficulty healing due to alterations in the macrovasculature, microvasculature, nervous, and immune systems.²³ Given these risks in this patient population, the importance of preventive care, including neuropathy screening and patient education, is paramount.

It is the author’s opinion that companies that sell metal-containing socks should consider warning statements regarding the use of their product by patients who have decreased sensation in situations where heat could be an issue. Health care providers who recommend their use and persons who work in settings where metal-infused clothing are sold should also be informed about the possible risk of these products when used by patients with sensory impairment.

This case report describes a 68-year-old man with diabetes who sustained a third-degree burn to his neuropathic leg while wearing a copper-containing compression sock for several hours in the sun. Patients with diabetes, and especially patients with diabetes and neuropathy, are at risk of developing more severe burns as well as complications following thermal injury, which makes it paramount that they receive education about burn prevention. Such education should be specific regarding possible sources of burns. Future research is recommended to examine the thermal conductivity of metal-containing clothing.

Anne Gallentine is a physical therapy supervisor, Park Nicollet Methodist Hospital, St Louis Park, MN.

Address all correspondence to: Anne Gallentine, Park Nicollet Methodist Hospital, 5845 Division St, Shorewood, MN 55331; tel: 952-993-7056; email: gallea@healthpartners.com.