AFOs and Interfaces: The Important Role of Socks
Padded socks: The evidence
A body of research supports the notion that padded socks can provide effective protection against the plantar pressure and shear forces that can lead to damage in the compromised foot.
Plantar pressure. The first study of the pressure relief characteristics of padded socks was done at the Manchester Royal Infirmary in the UK. Veves et al showed that padded hosiery were associated with significantly lower peak forefoot plantar pressure and pressure time integral than a barefoot condition in patients with diabetic neuropathy. 9 A subsequent study by the same group10 showed that specially designed high-density padded socks, as well as less dense sport-specific padded socks, demonstrated pressure-reduction benefits, with the higher density padded socks providing more pressure relief than the sports socks. In a separate experiment reported in the same article, the authors also found that the high-density padded socks provided significant pressure relief for six months of continued use. 10
Another study by Veves et al found that, in patients with painful rheumatoid arthritis, high-density padded socks were associated with significantly lower pressure than a barefoot condition; high-density and medium-density padded socks were both associated with significant pain relief compared with the patients’ usual socks. 11 A later study by Garrow et al 12 showed that multilayered socks were associated with significantly lower values for total foot pressure and peak forefoot pressure than ordinary socks in patients with diabetes at high risk for foot ulceration. However, the degree of pressure reduction was greater for the padded socks studied by Veves et al than the multilayered socks studied by Garrow et al (25% to 30% for the padded socks vs 9% for the multilayered socks).
Blisters and shear force. Two landmark studies by Herring and Richie showed that padded socks reduced the frequency and severity of blisters in long distance runners. 13,14 These studies were important because they demonstrated the advantages of padded socks made from synthetic fiber (specifically, acrylic fiber) over socks made from natural fiber (cotton). The studies showed the padded sock design made with acrylic fiber reduced blister frequency and severity more effectively than its natural-fiber counterpart and managed the moisture that can contribute to skin maceration and blister formation.
The researchers observed that, “The denser padded sock appears to enhance the effectiveness of acrylic fibers compared with cotton by providing a thicker anatomically distributed framework of material to dissipate shearing forces and an effective interstitial framework to enhance the wicking mechanism and provide optimal moisture environment on the pedal skin surface. If coaches, athletic trainers, and health professionals are to recommend acrylic fiber socks for active people, clarification should be made that acrylic fiber socks must be constructed with dense padding to enhance the physical properties of the fibers.” 14
Although these studies were done in the 1990s, they are still relevant today. Padded sock technology has not changed appreciably. Advances in engineered synthetic fibers to enhance wicking and to improve insulation, as well as nanofibers that allow the release and application of agents such as moisturizers on the skin, are illustrative of the advances in textile technology that have occurred; however, none of these advances affect the protective qualities of padded socks in reducing interface pressures with AFOs.
Putting it into practice
Taken together, the vulnerabilities of the skin and soft tissues of the feet and lower legs during AFO use and the research about padded sock protective capabilities have convinced me the comfort and effectiveness of AFOs can be enhanced with the use of properly designed padded socks. To accomplish this, I have incorporated four steps into my clinical practice routine when creating, fitting, and adjusting AFOs:
1. The use of padded socks with all of our AFOs. Padding in the foot area is especially helpful for people who plan to participate in active sports or who have conditions such as neuropathy that compromise the ability to feel damage to the feet. It is important that the sock material wick moisture away from the foot to help prevent blistering and other foot lesions, as well as fungal or bacterial infections. I suggest avoiding natural fibers (cotton, wool, and silk) because they are hydrophilic. 15
As noted previously, acrylic and acrylic blends have been shown to have effective protective and moisture wicking characteristics. I also recommend avoiding thin nylon or other thin synthetic materials, as they offer virtually no protection for the skin and soft tissues of the lower extremity. They also can be slippery, causing the patient’s foot or leg to move around in the device, which can contribute to instability and increase the risk of a fall or soft tissue injury. I advise patients to change socks at least twice a day, and more often if they live in a warm climate or engage in moderate-to-vigorous activities. In most cases (depending on the specific AFO design), an over-the-calf sock style should be considered to help protect the tissue of the lower leg from chafing and irritation.
2. Discussion with patients about the use of padded socks before fitting. I regularly have conversations about socks, as well as footwear, when I am preparing to create an AFO. Yet time and again, patients who have had an AFO previously—or simply have worn off-the-shelf foot orthoses—will say, “Oh, I’ve never heard that before. No one ever asked me about my activities or what socks I might wear.” Many practitioners do talk to patients about footwear and the importance of making sure shoes are big enough to accommodate the AFO, but they don’t often talk about the interface. The discussion about socks should take place up front, when taking measurements for the AFO.
3. Ensuring the patient’s shoes can accommodate both the orthosis and the padded socks. Proper fitting of footwear is important, just as proper fitting and alignment of the AFO is important. If the padded sock-AFO combination makes the patient’s shoes too tight, I recommend that he or she purchase new slightly larger shoes that have sufficient volume for all the components.
4. Consider the padded sock, AFO, and the patient’s footwear as a system, in which the components work together to create a robust interface between the skin and soft tissue and the AFO. This can help minimize soreness and other foot conditions. In my experience, careful attention to a system-based fitting approach—that is, choosing the padded sock, designing and fitting the orthosis, and ensuring a comfortable and effective fit with the patient’s footwear—can help minimize the need for AFO adjustments going forward. I do this by finding out what activities the patient engages in, recommending the appropriate padded socks, and taking the thickness of those socks into consideration early in the design process. Then the extra volume that will be required for the padded sock can be taken into account in the positive model before completing the vacuum forming process for the orthosis.