Socks serve important functions in the orthotic and prosthetic profession, but with the overwhelming number of options on the market, it can be difficult for a clinician to determine what qualities characterize an ideal candidate.

Prosthetic and diabetic socks are crucial for protecting the skin, maintaining socket fit and comfort, controlling moisture buildup and odor and preventing friction and abrasions. If any of these functions are compromised, the wearer could experience discomfort, blistering and volume fluctuation among other issues, so it is important that clinicians understand what they are looking for in a sock in order to better serve the needs of their patients.

Fabrication

Creating a proper sock begins with the fabrication.

“The way you make the fabric is important,” Joe Davant, the president and chief executive officer of Rx Textiles in Monroe, N.C., told O&P Business News. “The construction of the fabric, the weights of the yarn, the knit structure that you choose and the way you combine all those elements together is what makes it work.”

Although the knit construction will depend on the manufacturer and the desired purpose of the textile, seamless socks designed for the amputee and diabetic population are knitted on a flatbed knitting machine, beginning at the toe of the sock and working up to the top.

 

“Socks are knit on knitting machines that start at the distal end and knit a seamless product as well as fashioning the tapered shape of traditional multi-ply prosthetic socks,” Mark Smith, CP, the president and chief executive officer of Knit-Rite, Inc., said.

This technology can also produce a seamless toe, which is important for increasing comfort and reducing the risk for irritation or abrasion.

 

Prosthesis fit

Traditionally, prosthetic socks are used to control the fit of a prosthesis. If an amputee experiences fluctuation in limb size as he or she moves throughout the day, this issue is usually remedied by adding or removing a prosthetic sock or adjusting the ply of the sock between the prosthetic socket and the skin or liner.

“Throughout the day, the amputee may lose volume and could look to socks to compensate for that loss to help decrease socket fit related issues,” Kevin McLoone, vice president of business development for Alps in St. Petersburg, Fla., told O&P Business News. “[The sock] is going to compensate for that volume loss throughout the day.”

Wool has long been an ideal natural fiber candidate for prosthetic socks because it is durable and compliant. And according to Smith, wool has a “springy resiliency” that allows the fabric to maintain its shape and durability while also stretching to provide an ideal fit, which is crucial for both prosthetic and diabetic socks. Improper fit can cause a sock to wrinkle or bunch, creating blisters or abrasions, or cut off circulation to the limb.

“In any device, whether it’s a prosthesis or orthosis or diabetic shoe, the importance of reducing the incidence of wrinkles that can cause pressure points is the key factor,” Smith said. “And that’s where the high-stretch, core-spun yarns also provide a very effective solution.”

Wool also has a thermostatic property that will regulate body temperature and keep the wearer warm in cooler temperatures and cool when it is hot without added bulkiness. High-stretch yarns will also accommodate more patients and reduce the amount of sizes a clinician needs to keep in stock.

Many manufacturers will also fabricate socks with pre-cut holes in the distal end to be worn over pin liners. Prosthetic socks can create problems for these suspension systems because the fabric can unravel around the hole or jam the lock.

“The vast majority of prosthetic sock users are suffering from vascular related issues, so sometimes aligning the hole to the pin liner at the distal end of a sock can be challenging and often takes multiple attempts,” McLoone said. “So we have reinforced the hole at the closed end of the sock with plastic. So instead of the pin going through the knit, it will go through the hole and decrease the likelihood of the fabric causing the lock to jam.”

Rx Textiles fabricates a similar sock, which is designed for durability and convenience.

“Our Tuff Toe is specifically designed to work with pin liners,” Davant said. “We have a special seam that is sent around the hole to reinforce it, and then that’s reinforced with a gel, which increases the durability of the sock and helps avoid lock jams.”

Skin protection

Another critical task for both prosthetic and diabetic socks is protection of the skin.

“You want to transfer moisture and perspiration away from the skin, which is why prosthetic socks historically have been made of wool,” Smith said. “Wool has a way to handle perspiration really well and keep the skin dry.”

Unlike cotton, which will remain wet once moisture has entered the fibers, wool is naturally moisture-wicking. However, according to Smith, the beneficial properties of wool are enhanced when blended with synthetic fibers. Knit-Rite now blends Coolmax fibers into their socks. Coolmax is a patented fiber developed by DuPont Textiles that utilizes specially engineered polyester fibers to improve the function of the fabric. The fibers utilize a four- or six-channel transport system to wick moisture away from the skin and toward the outside layer of the fabric.

Alps also incorporates Coolmax technology into their socks to manage moisture.

“We feel this is the best [material] for practitioners to select because the properties of the material allow it to wick moisture away from the yarn itself,” McLoone said. “If a sock is worn directly up against the skin, we feel that Coolmax is by far the best material.”

Similarly, developers at Swiftwick, a manufacturer of high-performance socks in Brentwood, Tenn., identified the need for a moisture-controlling amputee sock with the help of transtibial amputee John Mabry.

“For a long time, I saw the need for managing moisture inside of the liners,” Mabry said. “And then I got a pair of Swiftwick socks at a race in Nashville, and I tried them on was blown away by how comfortable they felt.

“I met the president of Swiftwick and saw the technology used for their high-performance compression socks and thought that it would be an ideal match to put their technology toward a liner for amputees,” Mabry said.

Mabry eventually joined the Swiftwick team and helped develop the Valor liner sock. The Valor sock is knitted on a flatbed knitting machine, similar to most prosthetic socks, and utilizes a synthetic fiber called olefin, originally used in carpets.

“Olefin is a hollow fiber, so we are able to store the sweat naturally inside of the hollow fibers,” Mabry said. “The sweat is pulled away from the skin and inside of the hollow fibers of the sock.”

Olefin is extremely durable and holds .01% of its weight in moisture, ensuring that the sock will remain dry and light.

“We have one simple solution that’s cost-effective and made in America,” Mabry said. “I am able to put it on in the morning and take it off at night and not have to stress about adjusting my leg throughout the day.”

 

Antimicrobial properties

“One of the big developments in skin and prosthetic-interface technology was the roll-on liner,” Smith said. “But when people started using prosthetic liners next to the skin, it changed how socks are used for skin protection.”

Prosthetic liners can present several issues for amputees, including bacteria and moisture build-up and odor. One way to manage these issues is with the use of a moisture-wicking prosthetic sock that is worn over the skin, but underneath the prosthetic liner.

In addition to moisture management, controlling bacteria growth is also an important quality in a textile.

“Basically, you are putting the person’s skin and residual limb in a closed environment that doesn’t breathe,” Smith told O&P Business News. “Sometimes people have issues with dermatitis as a result of bacteria and perspiration living next to their skin for long periods.”

To combat bacteria growth, many manufacturers integrate antimicrobial properties, such as silver, into their fabrics.

“Silver is a natural antimicrobial,” Smith said. “It significantly reduces the bacterial population in the skin environment, and it has become a popular fiber in prosthetic and orthotic interfaces.

“To address the skin issues people were having with liners, we were able to combine silver and wicking fibers in a ‘liner liner’ prosthetic sock that has provided an effective solution. But with this product we had to knit it as sheer as possible so that it doesn’t interfere with the suction suspension function of the liner, as well as on a flatbed machine so it has a truly seamless distal end within the liner,” Smith said.

The Valor sock also uses patented antimicrobial silver molecules to kill bacteria and reduce odor.

“The silver in our socks is evenly distributed with even-sized particles, and each particle basically has its own armor case around it, so it won’t get washed out,” Mabry said. “Most of our users have noticed a significant reduction in odor.”

Another popular choice for antibacterial benefits is bamboo. Bamboo is naturally sustainable, soft and porous and has natural antimicrobial properties. It can also be blended well with other textiles. Sockwell, the therapeutic performance division of Goodhew, a sock manufacturer in Chattanooga, Tenn., utilizes bamboo in a blend of yarn they call cashmerino bamboo.

“The cashmerino is a micron wool that is blended with bamboo, so it’s a high performance blend of yarn,” Mercedes Marchand, vice president of design and merchandising for Sockwell, told O&P Business News. “It has natural moisture management, natural odor control and natural thermoregulation, and with the wool and bamboo together, it is antimicrobial and antibacterial.”

Despite the antimicrobial molecule used in the textile, moisture-management is going to be the most important step in controlling bacteria growth and odor.

“If you manage the moisture, then it gives the bacteria less of a place to grow,” Marchand said.

Compression technology

Compression therapy can be important for both amputees and diabetic patients. In diabetic patients, light compression is sometimes recommended for improving circulation in the limbs, particularly in patients who also have poor venous return, so manufacturers often employ the use of compression in the sock.

“Within our graduated compression series, we have two levels of compression,” Marchand said. “The 15-20 mmHg is moderate compression that is recommended for all-day wear, and the 20-30 mmHg is firm compression.”

Both compression levels are designed to improve circulation by placing pressure on the veins to stimulate blood circulation back towards the heart.

Compression therapy is also important for amputees, because it can manage limb volume and improve recovery time in new amputees. The Valor sock, for example, utilizes compression therapy at 30 mmHg to address these issues.

“We’ve had a number of wearers report that they have maintained a more consistent limb volume throughout the day while wearing the Valor sock,” Mabry said. “It’s not overly compressive but provides just enough compression to keep you comfortable.”

 

“Amputee compression therapy is another category for which the benefits of silver apply,” added Smith. “Bacteria and odor are also concerns for prosthetic shrinker wearers, exspecially post-operatively, and offering silver in the construction of shrinkers helps to limit that.”

Regulation

Whereas prosthetic socks are typically reimburseable, there are no standards or regulations to determine what qualifies as a diabetic sock. This is especially important for diabetic patients, who may not understand the importance of wearing appropriate socks.

“The diabetic footwear explosion happened in the early 2000s, and wit that, foot care providers started recommending that diabetics wear diabetic socks,” Ron Hercules, executive vice president of Knit-Rite, said. “But no one regulates what a diabetic sock is, and there are a lot of manufacturers out there claiming they have a diabetic sock, but unfortunately often they have done little or nothing to their sock to make it a diabetic sock.”

Diabetic socks should be seamless and form-fitting. They should wick moisture and incorporate an unrestricted top, among other characteristics, but without a regulating body enforcing guidelines, any manufacturer can claim to produce a sock designed for the diabetic population. And this can cause confusion among consumers if they are doing so at a lower cost.

“The problem is that producing the right features [in diabetic socks] is pricey,” Hercules said. “Some stores carry diabetic socks made of cotton that are very inexpensive, maybe $2 or $3, but cotton is exactly what a diabetic should not wear. They absorb moisture and become clammy and usually have a seam on them and can cause pressure points over neuropathic toes.”

But for a patient on a fixed budget, paying for a good-quality diabetic sock, which can cost anywhere from $10 to $30 and is usually not covered by insurance, may seem frivolous. In an effort to encourage patients with diabetes to purchase appropriate socks, manufacturers, such as Sockwell, are incorporating bright colors and fun patterns into their designs.

“Our product doesn’t look like a medical product,” Marchand said. “We have fun colors for women and men, as well as patterns. They are completely fun, so this is fashion and luxury and performance at the same time.”

Even with appealing fashions and trends, many patients may be hesitant to purchase, so it is important that doctors and clinicians educate their patients about what to look for in an appropriate sock and the risks that can arise from improper materials.

Manufacturers also encourage clinicians to approach them with any needs or issues they may see with current products.

“We will work with our customers in the industry to develop fabrics that will work specifically for their needs,” Davant said.

“What we have endeavored to do in terms of our products is be responsive to the needs of practitioners in the industry,” Smith said. “We try to listen to practitioners and hear what their needs are and try to respond to the specific clinical problems with solutions.” — by Megan Gilbride

 

Disclosure: Smith and Hercules are employed by Knit-Rite. Davant is the president and chief executive officer of Rx Textiles. Marchand is employed by Goodhew. McLoone is employed by Alps. Mabry is employed by Swiftwick.Disclosure: O&P Business News does not endorse any company or products mentioned herein. Not all companies or products relevant to the topic are represented.