the sample size was small 14 (males 10, females 4), the period of the intervention is short (six weeks) which is not sufficient for insoles to make an effect on the medial arch or evaluate long-term effect. (Kim and Kim, 2016)
While in this study they evaluated the effect of orthotics in different walking conditions, it was conducted for 3 months, the shoe and orthotics were standard for all patients, the orthotic measurement was (thickness arch 2.6 cm, and the thickness of fore foot and heel was 0.4 cm), the parameters assessed were the load rate and contact area from planter pressure, the study resulted in an increase in the height of foot arch and there was a change from midfoot in weight-bearing to heel and fore foot, which lead to decrease in the midfoot contact area and load rate. The correction of planter pressure was found in horizontal ground and in walking up and down stairs. The limitations include the sample size was small 15, they didn’t measure the changes in the arch height.(Zhai et al., 2016)
Another study compared the prefabricated and proprioceptive foot orthoses effect during walking on the distribution of plantar pressure, in the prefabricated orthotic group the orthotic supported the longitudinal arch and was 1-mm-thick while the proprioceptive orthotic group the orthotic was a flat with no arch support. The parameters assessed were peak pressure, maximum force, and contact area, it resulted in the prefabricated insole there was no major differences in contact area, while a significant decrease in peak pressure and force was noted, this reduction of the heel pressure is due to structural mechanisms of supporting the medial arch that lead to load transfer into midfoot area and in realigning the calcaneus to be in a normal position, thus leading to changes in pressure distribution. The limitations include the sample size is small 12 and they were male only, they assessed it in walking condition, the study didn’t evaluate long-term effect.(Aminian et al., 2013)
Masamitsu Kidoa study evaluated the load response in medial arch to assess the effectiveness of the insoles in supporting the medial arch, they used two types of insoles accessory insoles and therapeutic insole which raised the arch by 10 mm with a 5-mm inner wedge, the parameters assessed include the load response, it resulted in that it was significant that the therapeutic insole suppressed talocalcaneal joint eversion compered to the accessory insole, limitations include the sample size is small 8 (males 4, females 4), they assessed it in mimicking a standing condition, the study didn’t evaluate long term effect.
In Hassan Saeedi study, they evaluated the effect of a customized orthoses done by University of California Berkeley Laboratory and its impact on muscle activity and kinetic, the parameters assessed were Foot skeletal alignment, visual analog scale, muscle activity (tibialis anterior, peroneus longus and medial gastrocnemius), ground reaction force. The study resulted in there was a correction in the alignment of the foot, the VAS results were reduced, the foot is functioning with a less load on the soft tissue, the limitations include they only used one subject in the study, it was for one month hence no long-term effect can be given.(Saeedi et al., 2014)
After reviewing these study results in the matter of orthosis effect on the medial arch, we can observe that there is a need in increasing the sample number, and in investigating the long-term effect of orthosis and measurement of the arch height which leads to the conclusion of the medial arch in flexible flatfoot to be realigned.