Effects of orthotic insoles on adults with flexible flatfoot under different walking conditions
[Purpose] This study was to evaluate the effects of orthotics on adults with flexible flatfoot when wearing orthotic insoles while walking on horizontal ground, walking up and down stairs and to determine if flexible flatfoot needs treatment. [Subjects and Methods] Fifteen college students with flexible flatfoot and fifteen college students with normal feet were recruited. First, load rate and contact area were measured by RSscan force plate when the subjects were walking on horizontal ground, walking up and down 10 cm and 20 cm stairs. Then the subjects with flexible flatfoot were instructed to wear orthotic insoles for 3 months, and plantar pressure was measured again. Finally, the data were subjected to repeated measures ANOVA. [Results] After treatment for 3 months, the plantar pressure of flatfoot was significantly improved. In addition, the data of the subjects with normal feet and flatfoot were significantly influenced by walking down 10 cm or 20 cm stairs. [Conclusion] Orthotic insoles could significantly improve the plantar pressure of flatfoot. Additionally, the arches of subjects with normal feet and flatfoot can be significantly deformed when walking down stairs. Therefore, it is essential for subjects with flexible flatfoot to wear orthotic insoles to avoid needless injury.
Keywords: Flexible flatfoot, Plantar pressure, Orthotic insoles
Flatfoot, also called pes planus or low arch, refers to a condition in which the medial longitudinal arch is flat or missing and is one of the common deformities included in lower limbs diseases1). Because the alignment of the foot is in disorder2), changes in foot structure occur that cause other conditions like ankle arthritis3), pollex valgus4), and foot pain5).
Flatfoot can be divided into rigid flatfoot and flexible flatfoot by its structure6). The arch of the foot in the former case is always flat when one is in a weight-bearing or non-weight-bearing position, and it will result in pain or other discomfort7). However, the arch of the foot in the latter case is flat only in a weight-bearing position; in a non-weight-bearing position, the foot arch is the same as in the case of a normal foot8).
Due to the fact that the arch is always missing in the case of rigid flatfoot, surgical treatment is generally needed to correct the structure of the bones9). In contrast, the arch in the case of flexible flatfoot is so plastic that conservative physiotherapy can achieve a corrective effect10). However, sufficient attention has not been paid to the conservative treatment of flexible flatfoot. Furthermore, whether flexible flatfoot needs treatment has always been controversial.
The orthotic insole is a tool used in physiotherapy; however, its effects have not been clarified. Previous studies have only estimated conservative effects of orthotic on the plantar pressure of individuals with flatfoot on horizontal ground11,12,13), how plantar pressure data vary when walking up and down stairs has not been studied. Therefore, this study measured the data of subjects under different walking conditions to evaluate the effects by wearing orthotic insoles and further determine if conservative treatment is needed.
SUBJECTS AND METHODS
This study was approved by the Ethics Committee of the First Affiliated Hospital of Xi’an Jiaotong University, and informed consent was provided by the subjects.
Fifteen adults with flexible flatfoot and fifteen adults with normal feet were recruited after determining their status by collecting their foot prints using an RSscan force plate. All subjects were college students who had not had any lower limb diseases in the past 6 months. There was no significant difference in age, height, weight, or foot length between subjects with flexible flatfoot and subjects with normal feet. For the subjects with flatfoot, the arch was missing in a load-bearing position, the proportion of the midfoot print between the hollow area and solid area was 1/2, or the hollow area was missing. For the subjects with normal feet, the arch was always present, and the proportion was 2/1.
This study used an RSscan force plate (RS footscan USB 7), which has an area of 40 × 50 cm and 4,096 sensors; this device can measure dynamic plantar pressure. The foot was automaticlly divided into 10 parts by the plate, including toe 1, toes 2–5, the first metatarsal bone, the second metatarsal bone, the third metatarsal bone, the forth metatarsal bone, the fifth metatarsal bone, the mid foot, the medial heel, and the lateral heel. Due to the arch of the midfoot being the main difference between a flatfoot and normal foot14), this study focused on only the load rate and contact area of the midfoot.
After performing walking exercise several times, the subjects were asked to walk on horizontal ground and to walk up or down 10 cm or 20 cm stairs at one step per second in socks (the same socks for each subject) while not wearing shoes. Under each walking condition, the RSscan force plate was used to record data for load rate and contact area. Each variable was measured 3 times, and the mean value was calculated. Then the subjects with flexible flatfoot were asked to wear shoes (the same shoes for each subject) containing the orthotic insoles 8 hours per day for 3 months, and plantar pressure was measured again after treatment. Once recording of data was complete, the data were divided into the following 3 groups: flatfoot before treatment, flatfoot after treatment, and normal feet. Each group was further divided according to 5 walking conditions: walking on horizontal ground, walking up 10 cm stairs, walking up 20 cm stairs, walking down 10 cm stairs, and walking down 20 cm stairs. Repeated measures ANOVA was performed using spss 13.0, and the level of significance was set at p<0.05. The 95% confidence interval (CI) (p<0.05) was considered statistically significant. The 5 walking conditions were considered within-subjects variables, and the 3 groups were considered between-subjects factors.
This study measured the dynamic load rate and contact area by RSscan force plate in subjects walking under different conditions. The load rate (in N/ms) can be used to indicate the load-bearing ratio for various regions of the foot per millisecond15). The contact area can be used to indicate the area of contact between various regions of the foot and the ground, and it is shown in square centimeters16). The values for both of these variables are larger in the midfoot in individuals with flatfoot compared with those with normal feet17). Because the arch of the foot is decreased in individuals with flatfoot in a weight-bearing position, the structure of the bones of the foot is further deformed, which makes both the contact area and load rate of the midfoot larger.
The orthotic insoles in this study were made of an EVA resin material that was a copolymer of ethylene and vinyl acetate. The thickness of foot arch was 2.6 cm, and the thickness of fore foot and heel was 0.4 cm.
All the results indicated that although there was still a difference between subjects with flatfoot after treatment and those with normal feet, the data for load rate and contact area were significantly corrected under the different conditions, especially when walking down stairs. In other words, the data of the subjects with flatfoot changed after treatment, becoming more similar to the data of the subjects with normal feet.
Furthermore, the 95% CIs for walking down stairs did not intersect with those for any other walking conditions (Tables 3 andand 4). 4). This showed that the arches of the subjects with normal feet, in addition to those with flexible flatfoot, were deformed when walking down 10 cm stairs or 20 cm stairs.
The present study showed that the load rate and contact area of the subjects with flexible flatfoot were larger than those of the subjects with normal feet, which was consistent with previous studies18,19,20). However, the data revealed that these variables were corrected effectively after 3 months of treatment consisting of wearing orthotic insoles. The results could be explained by the orthotic insoles increasing the arch height of the foot and correcting the alignment of foot bones, which could further improve plantar pressure21). With the increase in the height of foot arch, the weight-bearing sites were changed from the midfoot to the fore foot and heel. Therefore, the contact area and load rate of the midfoot were decreased. However, due to the limited time of orthotic treatment, there was still a significant difference between the subjects with flatfoot after treatment and those with normal feet.
Previous studies only focused on the effects of orthotics on plantar pressure on horizontal ground18,19,20). None had estimated the effects of orthotics on plantar pressure while walking up and down stairs. In this study, it was observed that orthotic insoles could correct the plantar pressure of subjects with flatfoot not only on horizontal ground, but also when walking up and down stairs. This may because the orthotics were able to correct the abnormal structure of the foot22), suppress the eversion of the talocalcaneal joint23), and further improve the joint angles of the lower limbs while walking up and down stairs.
It should be noted, however, that the highest values for load rate and contact area were for walking down 20 cm stairs and that the second highest values were for walking down 10 cm stairs. This may be due to the fact that when someone is going down stairs, the plantar pressure of the midfoot is affected not only by the body weight but is also affected by the acceleration of gravity, which causes greater loading of the midfoot24). Therefore, when walking down stairs, the plantar pressure became larger with the increase in stair height.
It should also be noted that the values for load rate and contact area when walking down stairs were significantly larger than when walking on horizontal ground or up stairs in both groups of subjects. This shows that when walking down stairs, the arch of the foot is deformed badly not only in subjects with flatfoot but also in those with normal feet. In individuals with normal feet, the arch of the foot needs a certain amount of elasticity to protect plantar vessels and nerves from compression25); however, the arch can be influenced by the impact of the foot with the stairs when walking down stairs. In individuals with flatfoot, the stability of the arch is so weak that it is more easily deformed when walking down stairs. That is to say, walking down stairs is harmful to the arch of the foot. This is important because people generally choose to take an elevator when traveling to higher floors in a building, but when traveling to lower floors, they generally prefer to take the stairs rather than wait for an elevator, as long as the number of floors is not too high.
Finally, insufficient attention has been paid to the conservative treatment of flexible flatfoot, and whether adults with flexible flatfoot need to be treated has always been controversial2, 10). The present study shows that flatfeet and even normal feet are influenced by walking down stairs. Furthermore, none of the participants experienced discomfort during the treatment, and the therapeutic effects were apparent. Therefore, use of orthotic insoles could be recommended for treatment of flexible flatfoot to prevent further development. However, further study should be conducted to estimate the effects of orthotics on other plantar pressure variables in the future.
Fight Back Against Foot Pain
Orthotics can help, and they don't have to cost a fortune
If your feet ache after a day of walking and you’re looking for relief, you’re not alone.
In 2015 Americans spent about $4.7 billion on orthotics sold in supermarkets, drugstores, sporting goods shops, and online. The products include flat pads as well as inserts designed to support arches, stabilize heels, or take pressure off areas of the feet that hurt or are rubbed by footwear.
Custom orthotics require an evaluation by a foot expert such as a podiatrist and can cost hundreds of dollars, with insurance picking up little to none of the tab. But over-the-counter inserts often cost less than $10. Best of all, there's evidence that for some people with foot pain, they actually work.
“A $50 pair of orthotics could potentially be as effective as a $400 to $500 custom pair,” says Reed Ferber, Ph.D., director of the University of Calgary’s Running Injury Clinic.
In several studies, over-the-counter orthotics significantly eased common heel and foot pain problems that can make walking, doing chores, and generally being active problematic.
In one large review of the effectiveness of pricey podiatrist-crafted orthotics, researchers from Australia’s University of Newcastle concluded that drugstore types were just as good as expensive custom orthotics for several types of foot pain. An older University of California study found that over-the-counter inserts worked better than custom models for one type of plantar fasciitis (a common ailment in which a thick band of tissue on the bottom of the foot becomes inflamed).
And orthotics can help a wide range of people with aching feet, not just serious athletes. Foot orthotics "can be used among many different populations to effectively treat pain and improve functional capability, from children to older adults, and from the sedentary to elite-level athletes," says Daniel Bonanno, a podiatry lecturer at La Trobe University in Australia.
Who Should Consider an OTC Orthotic?
If you have diabetes or circulation problems—which can cause foot ulcers and infections—the American Podiatric Medical Association advises talking to a healthcare professional before trying out an over-the-counter orthotic. A podiatrist can find solutions for foot- and leg-pain issues that won’t rub or irritate your feet.
If you're otherwise healthy but are experiencing foot pain, experts say over-the-counter insoles can be a good option.
Just remember that they're intended to help ease foot pain, not something more complex, like back pain. “They work best for foot pain of all sorts," including ankle pain and shin pain, notes Ferber, who has studied prefabricated orthotics extensively. “But they’re less effective for knee, hip, and lower back pain. There are so many more variables involved with discomfort in those areas.”
Over-the-counter solutions may not correct underlying problems that can cause long-lasting discomfort as effectively as custom inserts. But Ferber says they can come close—with significant money and time savings for patients who don't go the custom route.
For the best results, Ferber recommends that people experiencing foot pain try calf raises in addition to using orthotics. While standing with feet shoulder-width apart, raise up on your toes for 2 seconds, then lower your feet to the ground slowly (about 2 seconds). Hold onto a countertop or sturdy chair for support. “Do 20 to 60 a day," he says. "This one exercise strengthens nine muscles that support the structure of your foot and propel you forward with every step. It can help fallen arches, heel pain, ankle pain, and shin pain.”
How to Shop for an Orthotic
Bring the shoes you plan to use with your new orthotics. Try the orthotics in them. They should feel good right away.
Zero in on your needs. If you have mild-to-moderate allover foot aches after being on your feet for a while, you may just need a flat, cushioned insole. If you have heel pain or pain in your arches, look for inserts that provide arch support and/or types that cushion and/or stabilize your heel. If you have pain at your arch, try arch supports.
Let comfort and support guide your choice. With hundreds of options available, Ferber says those considerations are the best rule of thumb for making a selection. “It may not sound scientific, but there’s actually plenty of evidence that an orthotic that feels comfortable and supportive for your needs is the one that will work the best for you," he says. "Everyone’s feet and walking patterns are slightly different. Wearing an orthotic that doesn’t feel right can make you change your gait. And even slight changes can cause injuries.”
Remember: If pain is severe or not helped within two weeks by an over-the-counter orthotic, it’s worth seeing a podiatrist for a diagnosis and pain-relief plan.