Flexible flat foot or pes planovalgus is a common foot deformity, and silicone and customized insole are commonly used as a non-operative treatment modality of flexible planovalgus.
Amit Kumar Vimal et al conducted a study to quantify and compare the radiological parameters immediately on weightbearing with silicon and customized insoles and without them to assess the effect on midfoot and hindfoot of the flexible planovalgus in adults.
A total number of 11 (8 females and 3 males) subjects with flexible pes planovalgus deformity without any other foot deformity were included in the study. Each patient was assessed three times in a random sequence without and with use of either silicon insoles or customized insole. The radiographic parameters without insole, with silicon insole, and with customized insole conditions were calculated using online available computer software Kinovea.
One-way ANOVA analysis was performed between groups (without insole, with silicone insole and with customized insole). The results of the study were:
The hindfoot parameters depicted that calcaneal inclination angle (CIA) was significant increased (P=0.000) and talar declination angle (TDA) was significantly decreased (P=0.003) only with the use of customized insole compared to without insole.
The midfoot parameters depicted that the first metatarsal angle (FMA) and talonavicular coverage angle (TCA) were significantly lower with customized insole (P=0.00) as compared to other two groups and significantly lower with silicone insole (P=0.00) as compared to without insole group.
This study implies that the rigidity of the insole is also a factor in the efect of foot orthosis for pes planus. The results indicate that the compressibility of the insole material affects the forefoot and hindfoot biomechanics differently. Flexible medial arch support (silicone insole) increases the first metatarsal height with enhanced talonavicular coverage area, which is likely to alter the normal 45% of the weight bearing forces which occur in forefoot and midfoot. The customized rigid insole increases the CIA and decreases the TDA providing additional improvement of the hindfoot biomechanics where normally 55% of bodyweight is distributed. There was a radiological improvement on immediate weight bearing with the use of customized insole compared to silicone insole, particularly in the hindfoot.
The authors concluded that “the medial arch of the foot is not equally maintained by silicone and customized insole, since silicone insole affects only the midfoot and customized insole affects both midfoot and more importantly the hindfoot which bears 55% of bodyweight.”
The Effect of Customized and Silicon Insoles on Mid and Hindfoot in Adult Flexible Pes Planovalgus
Amit Kumar Vimal, Shivani Sharma et al
Indian Journal of Orthopaedics (2022) 56:1897–1905