Whether Flexible Flatfoot Needs the Treatment? An Observation of Plantar

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1 1 2 3 Whether Flexible Flatfoot Needs the Treatment? An Observation of Plantar Pressure Effects on Adults with Flexible Flatfoot by Wearing over the Counter Insoles When Walking on Level Surface, Upstairs and Downstairs JunNa Zhai MM1*, Jue Wang PhD2*, YuSheng Qiu PhD* 1 *From the Key Laboratory of Biomedical Information Engineering of Ministry of Education, and Research Center of Rehabilitation Science and Technology, School of Life Science and Technology, Xi an Jiaotong University; National Engineering Research Center of Health Care and Medical Devices; Xi an Jiaotong University Branch; Xi an, Shaanxi, P. R. China. 2 *From the Research Center of Rehabilitation Science and Technology, School of Life Science and Technology, Xi an Jiaotong University; Xi an, Shaanxi, P. R. China. * From Orthopaedics of The First Affiliated Hospital of Jiaotong University, Xi an, Shaanxi, P. R. China. *Corresponding authors: YuSheng Qiu yusheng.qiu@mail.xjtu.edu.cn Phone number: Mailing address: No.227 YanTa Road, Orthopaedics of Xi an JiaoTong University Affiliated, Xi an , Shaanxi, P.R.China. This work was funded by The Fund of Orthopedic Department of The First Affiliated Hospital of Xi an Jiaotong University. The authors declare that there is no conflict of 1

2 22 interest Abstract Background: Orthotic insole is one popular physiotherapy for flatfoot. However, the effects and if flexible flatfoot needs the treatment are not clear and how the plantar pressure change while walking upstairs and downstairs had not been studied. This study observed the plantar pressure of different walking condition to find out the answers. Methods: Fifteen adults with flexible flatfoot and fifteen adults with normal foot were examined while walking on a level surface, walking up and down 10 cm and 20 cm stairs before treatment. The max force and the arch index were acquired using the RSscan system. Then the subjects with flexible flatfoot were instructed to wear the orthotic insoles for 3 months and the plantar pressure were measured again after treatment. The repeated measure was performed to analyze the data. Results: Both max force and arch index of flatfoot after treatment were significantly decreased under different walking conditions (p<0.01). When walking down 10 cm and 20 cm stairs, the plantar data of both normal foot and flatfoot were significantly increased (p<0.05). Conclusion: Orthotic insoles could effectively improve the plantar pressure of flatfoot under different walking conditions. In addition, the arches of both normal foot and flatfoot were obviously influenced when walking downstairs. It is therefore 2

3 43 44 necessary to wear orthotic insoles for flexible flatfoot to prevent further deformation. Keywords: Flexible flatfoot; Plantar pressure; Orthotic insoles Introduction Flexible flatfoot is a common disease in lower limb deformities [1] that is characterized by the low medial longitudinal arch [2]. Due to the incorrect alignment of the foot bones [3], it would cause calcaneal eversion, talar adduction with plantarflexion and dorsolateral forefoot subluxation. The deformity will change the plantar pressure distribution and the gait over the time [4], producing a substantial impact on the quality of life of the patient [5]. Flat foot can be divided into rigid flatfoot and flexible flatfoot [6]. Regarding the former, the arch of the foot was always missing either in the weight-bearing position or non-weight-bearing position [7] and it needs operation to restore the missing arch [8]. As far as concerned the latter, the arch was missing only in the weight-bearing position, while in non-weight-bearing position, the arch is as the same as that of normal foot [9]. Due to the arch s flexibility, the methods of the treatment and whether the flexible flatfoot needs the treatment have always been controversial [10, 11]. Orthotic insole is a kind of popular physiotherapy. So far, previous studies had only focused on the effects of wearing orthotic insoles when walking on the level surface [12, 13]. However, the effects were mixed, and how the plantar pressure change while walking upstairs or downstairs has not been studied. 3

4 In this study, we examined the plantar pressure of flexible flatfoot before and after wearing orthotic insoles while walking on a level surface, walking up and down 10 cm and 20 cm stairs to estimate whether plantar pressure will be improved and further to find out if flexible flatfoot needs the treatment. Material and Methods Subject The study protocol was approved by the Institutional Review Board of The First Affiliate Hospital of Xi an Jiaotong University. All the participants signed the written informed consent prior to the study participation. Fifteen college students with flexible flatfoot and fifteen college students with normal feet were subjected to collecting the footprints by RSscan force plate by two researchers. 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. All the subjects were female students and there was no significant difference between flatfoot and normal foot in age, height, weight and foot length. None of the participants had suffered from any lower limb diseases in the past 6 months. Procedure Before the measurement, all the subjects need to take off their shoes, wear the unified socks and do the walking exercises at the speed of one step per second. Then 4

5 the subjects were firstly asked to walk on the level RSscan force plate; then, they were instructed to walk up or walk down 10 cm or 20 cm stairs on the instrument respectively. The max force and arch index of the foot were recorded by the RSscan system under those walking conditions. To ensure the accuracy, data were measured 3 times and an average was obtained. After all the data were collected, the subjects with flexible flatfoot were asked to wear the unified shoes with orthotic insoles 8 hours a day for 3 months. After the treatment, the max force and arch index were measured again. At last, the repeated measure of general linear model with a level of significance of p<0.05 was performed using spss The 95% confidence intervals (CIs) (p<0.05) was considered statistically significant. Equipment An RSscan force plate (RS-footscan 7 USB2 gait) with an area of cm, including 4 sensors in each square centimeter, was used to measure the dynamic data of max force and arch index under different walking conditions. When the subject was walking on the force plate, the foot was divided into 10 parts automatically including toe 1, toe 2-5, first metatarsal, second metatarsal, third metatarsal, forth metatarsal, fifth metatarsal, mid foot, medial heel and lateral heel. In addition, there is a main difference of plantar pressure in midfoot region between a normal foot and a flatfoot. For the normal foot, the main load-bearing regions include the metatarsal area and the heel area, but for the flatfoot, it not only includes the metatarsal and heel areas, but also includes the midfoot [14]. In other words, it is 5

6 the pressure of midfoot that differs the flatfoot from normal foot. Therefore, we only focused on the data of midfoot. Orthotics In this study, the orthotic insoles were over the counter orthotics which were made of EVA resin material that is a copolymer of ethylene and vinyl acetate. The thickness of foot arch is 2.6 cm, the thickness of fore foot and heel is 0.4 cm. Data Analysis This study measured two kinds of dynamic data, max force and arch index. With the progression of the disease, the arch will become flat, the structure of foot bones will be deformed which results in an increase pressure of the midfoot, further increase the max force [15] and arch index [16]. Max force, with the unit of Newton, is defined as the maximum of plantar pressure of one part of the foot [17]. Arch index, a proportion of the midfoot area and the whole foot area, is useful in determining the prevalence of flatfoot and possibly predicting pathologic foot conditions [18]. We focused on the max force of midfoot and the arch index. Before the data analysis, all the data were divided into three groups: flatfoot before treatment, flatfoot after treatment, and normal foot. Each group was further divided into five conditions: walking on level surface, walking up 10 cm stairs, walking up 20 cm stairs, walking down 10 cm stairs and walking down 20 cm stairs. When entering the spss 13.0 system, we firstly edited 6 columns (group, level, 10 cm upstairs, 20 cm upstairs, 10 cm downstairs, 20 cm downstairs) and 45 rows 6

7 ( fifteen rows for group 1, fifteen rows for group 2, fifteen rows for group 3) and imput the corresponding data respectively. Then we chose the repeated measure of general linear model with a level of significance of p<0.05 was performed using spss The 95% confidence intervals (CIs) (p<0.05) was considered statistically significant. Finally, we put 5 walking conditions as within-subjects variables, and 3 groups as between-subjects factors to analyse the data. Results The significant differences were found in max force and arch index before and after treatment (p<0.01), while there was still a significant difference between posttreatment foot and normal foot in both data. (p <0.01) (Table 1) (Table 2) In addition, there was no intersection of the 95% CIs of both data before and after treatment on 5 different walking conditions. However, there was an intersection between posttreatment foot and normal foot in both data when walking down 10 cm and 20 cm stairs. (Table 3) (Table 4) Furthermore, the 95% CIs of downstairs of both data did not intersect with any other walking conditions not only in flatfoot but also in normal foot. (Table 3) (Table 4) The results implied that although there was still a difference between posttreatment foot and normal foot, the plantar pressure of flatfoot were effectively decreased after treatment, especially when walking downstairs. Additionally, the arches of both normal foot and flatfoot were obviously deformed when walking down 10 cm and 20 7

8 cm stairs. Discussion Orthotic effects of max force and arch index The results showed that the max force and arch index of flatfoot were effectively decreased after wearing orthotic insoles, which was in accordance with previous studies [19, 20, 21, 22]. As orthotic insoles can support the form of the foot arch [23, 24], which reduces the load-bearing of midfoot and further decreases the max force of midfoot and arch index. However, although the plantar pressure of flatfoot were effectively improved, there was still a difference between posttreatment foot and normal foot. This may happend because the time of the treatment was not long enough. Orthotic effects on different walking conditions Previous study had already estimated that orthotic insoles could improve the plantar pressure of flatfoot when walking on a level surface [19, 20, 21, 22]. However, it has not been examined how the plantar pressure change when walking upstairs and downstairs. In this study, the max force and arch index were effectively decreased not only when walking on a level surface, but also when walking upstairs and downstairs after treatment. This result indicated that orthotic insoles could improve the plantar pressure of flatfoot [25] and the function could be explained by that since the insoles have always been maintaining the proper form of the foot and finally reducing the load-bearing of midfoot [26]. 8

9 On the one hand, the largest values of max force and arch index were in walking down 20 cm stairs, the second largest ones were in walking down 10 cm stairs, which may be due to the fact that the plantar pressure will be influenced not only by the body weight but also by the acceleration of gravity when a person walks downstairs [27]. Therefore, with the increase of the gravity, the plantar pressure would increase as well. On the other hand, according to this study, the data of both normal foot and flexible flatfoot were obviously larger when walking downstairs, illustrating that the arches of both normal foot and flatfoot were apparently deformed whenever walking down 10 cm stairs or 20 cm stairs. As the arch of normal foot needs certain elasticity to protect plantar vessels and nerves from compression [28], the arch could be influenced by the impact of downstairs. The arch of flatfoot were more easily influenced due to the weak stability [29]. In other words, it is harmful to the foot arch when walking downstairs. However, people prefer to taking a lift when walking upstairs, as for downstairs, as long as the floor is not much high, they would rather walk downstairs than wait for the lift. Furthermore, all the participants had no discomfort throughout the treatment, and the therapeutic effects were apparent. What is more, even the arch of normal foot will be influenced when walking downstairs, it therefore could be treated for flexible flatfoot to avoid further development. Conclusions 9

10 Orthotic insoles could effectively decrease the plantar pressure of flexible flatfoot not only when walking on a level surface but also when walking upstairs and downstairs. Additionally, the data of both normal foot and flexible flatfoot were influenced whenever walking down 10 cm or 20 cm stairs. Therefore, adults with flexible flatfoot may need to wear orthotic insoles to prevent further deformation. However, further studies are necessary to analyze the plantar pressure of adults with flatfoot in other areas in the future. Funding This study was supported by The National Natural Science Fund, numbered H Conflict of interest The authors declare that there is no conflict of interest

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15 Table 1 Max Force before and after treatment Left Group Group Mean Sig.(a) 95% confidence interval foot difference for difference(2) Right foot Lower bound Upper bound Before Before After (*) Normal (*) After Before (*) After Normal (*) Normal Before (*) After (*) Normal Group Group Mean Sig.(a) 95% confidence interval difference for difference(2) Lower bound Upper bound Before Before After (*) Normal (*) After Before (*) After Normal (*) Normal Before (*) After (*) Normal Based on estimated marginal means * The mean difference is significant at the 0.05 level. a Adjustment for multiple comparisons: Least Significant Difference (equivalent to no adjustments). Before, flatfoot before treatment; After, flatfoot after treatment; Normal, normal foot

16 Table 2 Arch index before and after treatment Left Group Group Mean Sig.(a) 95% confidence interval foot difference for difference(2) Right foot Lower bound Upper bound Before Before After 3.019(*) Normal 4.727(*) After Before (*) After Normal 1.708(*) Normal Before (*) After (*) Normal Group Group Mean Sig.(a) 95% confidence interval difference for difference(2) Lower bound Upper bound Before Before After 3.237(*) Normal 4.852(*) After Before (*) After Normal 1.615(*) Normal Before (*) After (*) Normal Based on estimated marginal means * The mean difference is significant at the 0.05 level. a Adjustment for multiple comparisons: Least Significant Difference (equivalent to no adjustments). Before, flatfoot before treatment; After, flatfoot after treatment; Normal, normal foot

17 Table 3 Max force of different walking conditions Left 95% confidence interval foot for difference(2) Mean Group Condition Std.error difference Lower Upper bound bound Before Level upstair10cm upstair20cm downstair10cm downstair20cm After Level upstair10cm upstair20cm downstair10cm downstair20cm Normal Level upstair10cm upstair20cm downstair10cm downstair20cm Right 95% confidence interval foot for difference(2) Mean Group Condition Std.error difference Lower Upper bound bound Before Level upstair10cm upstair20cm downstair10cm downstair20cm After Level upstair10cm upstair20cm downstair10cm downstair20cm Normal Level upstair10cm upstair20cm downstair10cm downstair20cm Before, flatfoot before treatment; After, flatfoot after treatment; Normal, normal foot

18 Table 4 Arch index of different walking conditions Left 95% confidence interval foot for difference(2) Mean Group Condition Std.error difference Lower Upper bound bound Before Level upstair10cm upstair20cm downstair10cm downstair20cm After Level upstair10cm upstair20cm downstair10cm downstair20cm Normal Level upstair10cm upstair20cm downstair10cm downstair20cm Right 95% confidence interval foot for difference(2) Mean Group Condition Std.error difference Lower Upper bound bound Before Level upstair10cm upstair20cm downstair10cm downstair20cm After Level upstair10cm upstair20cm downstair10cm downstair20cm Normal Level upstair10cm upstair20cm downstair10cm downstair20cm Before, flatfoot before treatment; After, flatfoot after treatment; Normal, normal foot