What Should Be the Determinant of Treatment for Juveniles with Flexible Flatfeet?

Background: It is still controversial that if juveniles with exible atfeet need to be treated. Some believed they did not need the treatment unless they felt pain after exercise. However, as living standards rise, the amount of exercise among teenagers is declining. The juveniles with exible atfeet don’t feel pain not because they don’t have symptoms, but because they rarely walk. This study recruited juveniles with exible atfoot to nd out if there was other determinant of treatment. Methods: We recruited an experimental group with 20 severe exible atfeet and a control group with 20 severe exible atfeet. The contact area and load rate were measured separately. Then the subjects of experimental group were treated by exercise therapy for 8 weeks, and the plantar pressure data were measured again. The repeated measure was used to analyze the data. Results: The contact area and load rate of mid foot decreased signicantly in experimental group after 8-week treatment. All the subjects of experimental group did not feel any uncomfortable during the treatment. While the two kinds of data in control group were not changed much between pre-after measurements. Conclusion: Exercise therapy could effectively improve the severe exible atfoot. If the juveniles with exible atfoot need the treatment should not depend on the symptoms only, but also on the severity. The juveniles with severe exible atfoot should be treated as soon as diagnosed.


Introduction
Flexible atfoot is common in juveniles 1 . However, if the juveniles with exible atfeet need to be treated is still controversial. Some scholars believed that teenagers were growing and developing, they did not need the additional treatment 2 and the exible atfoot normally disappeared during growth 3 . While others considered that they still needed to be treated if they felt pain 4 after walking or other exercise 5 .
Flexible atfoot means when the foot bears weight, the medial longitudinal arch is missing and the structure of the foot is deformed, while, when the foot does not bear weight, the arch is still present like the normal foot 6 . In this case, whether exible atfoot needs the treatment commonly depends on the symptoms of the foot after walking or exercising 7 . However, as living standards rise, the amount of exercise among teenagers is declining. That means the juveniles with exible atfoot don't feel tired or pain not because they don't have symptoms, but because they rarely walk. Therefore, if juveniles with exible atfoot need the treatment may not merely depend on the symptoms.
In this study, we recruited 2 groups of severe exible atfeet among juveniles. One was experimental group in which the subjects were treated for 8 weeks, the other was control group. The plantar pressure data were measured and recorded separately. After 8-week treatment, we measured the data of 2 groups again to nd out if juveniles with severe exible atfoot could be treated and if the severity could be the determinant of treatment.

Methods
We rstly collected footprints among juveniles aged 11-12. Secondly we chose the subjects with severe exible atfeet in whose footprints the ratio of solid area to hollow area in mid foot was 2:1, or there were no hollow area at all. Then we divided them into two groups according to their willingness to participate in experimental therapy. Finally, we recruited an experimental group with 20 severe exible atfeet and a control group with 20 severe exible atfeet. All the subjects claimed that they did not feel pain or tired in daily life.
After collecting the subjects, we separately measured the plantar pressure data of two groups. In this study, we mainly measured two data, one was contact area of mid foot, the other was load rate of mid foot. As the exible atfoot progresses, the arch will be deformed worse and will further lead to an abnormal increase in the contact area 8 and load rate 9 of the mid foot. Plantar contact area (in square centimeters) refers to the contact size between the plantar and the ground 10 . Plantar load rate is the plantar load-bearing ratio per millisecond, which was shown in N/ms 11 . Since the main difference between exible atfoot and normal foot is whether the arch of mid foot is at, the main plantar pressure difference between them is also in the mid foot 12 . Therefore, this study mainly measured the contact area of mid foot and the load rate of mid foot.
Before measuring the data, the subjects were told to take off their shoes and wear the uniform socks.
They needed to practice walking on the RSscan force plate at the speed of one step per second. When they were ready, the contact area of mid foot and load rate of mid foot were recorded by the RSscan system. All the data were measured three times to obtain the average value. Then the experimental group were treated by exercise therapy for 8 weeks. During treatment, they were told to do foot extension-exion exercise, valgus and varus exercise, and short-foot exercise. For each exercise, they needed to do 16-20 movements in one group, 5 groups at a time, twice a day. After 8-week treatment, the contact area and load rate of mid foot were measured again. The repeated measure of SPSS 18.0 was used to analyze the data. The 95% con dence intervals (CIs) (p < 0.05) was considered statistically signi cant.

Results
It was shown that the contact area of mid foot decreased apparently from 46.275 to 39.917 in Experimental group. And there was no intersection of 95% con dence intervals between pre-after treatment, indicating that the contact area of mid foot after treatment was signi cantly declined in experimental group. (Table 1) This result was consistent with the references above 8,10 . On the contrary, the contract area of mid foot in control group did not change much. The 95% con dence intervals intersected between pre-after measurement, showing that there was no signi cant difference between the rst and second measurements. (Table 1) Additionally, the load rate of mid foot in experimental group reduced effectively from 1.663 to 1.053. And there was no intersection of 95% con dence intervals between pre-after treatment, showing that there was signi cant difference in load rate of mid foot compared with pre-treatment. The result was also consistent with the references above 9,11 . However, the load rate of mid foot in control group was not changed much. The 95% con dence intervals intersected between rst and second measurements, showing that there was no signi cant difference between them. (Table 2). Besides, all the subjects did not feel any uncomfortable during the treatment.

Discussion
It was seen from the result that the contact area of mid foot and the load rate of mid foot were effectively lower than before. It was implied that the mid foot, in which the medial longitudinal arch was located, did not bear weight any longer just like the normal foot. In other words, because of the at arch, the contact area of mid foot became larger 13 , which further lead to the increase in the load rate of mid foot 12 . After treatment, the arches were not at any more, which resulted in the reduction of the plantar pressure. The result in this study was consistent with the references above. Furthermore, atfoot is famous for its at medial longitudinal arch. The main reason leading to the at arch is that the muscular strength of tibialis anterior muscle, tibialis posterior muscle 14 , and the intrinsic muscles were too weak to hold the arch 15 . The result of this study indicated that after 8-week treatment, the plantar pressure data of juveniles with severe exible atfoot were signi cantly reduced. That means doing extension-exion exercise, valgus and varus exercise, and short-foot exercise can helpfully increase the muscular strength. This result was consistent with the references above.
However, in the control group, the contact area of mid foot and load rate of mid foot were not signi cantly changed between pre-after measurements. As the improvement of living standards, the juveniles seldom walk, not to mention the exercise of lower limb muscles. Therefore, the exible atfoot came quietly among the juveniles, even if they did not feel pain or uncomfortable, it didn't mean they did not need the treatment at all. As we all have known that, exible atfoot could cause more diseases such like strephexopodia, disorder of foot bone, ankle disease and even knee and hip problems, the juveniles with severe exible atfoot should be treated as soon as diagnosed. Whether juveniles with exible atfoot needs the treatment should also depend on the severity but not merely on symptoms.

Conclusion
The contact area and load rate of mid foot were signi cantly declined after treatment. Exercise therapy could effectively improve the severe exible atfoot. If the juveniles with exible atfoot need the treatment should not depend on the symptoms only, but also on the severity. The juveniles with severe exible atfoot should be treated as soon as diagnosed.

Declarations
The study protocol was approved by the Institutional Review Board of The First A liated Hospital of Xi'an Jiaotong University. All the participants signed the written informed consent prior to the study participation.