Flatfoot is a type of deformity morphologically caused by the collapse of the plantar arch and by a valgus deformity of the hindfoot; from the functional view point the foot is kept prevalently or persistently over-pronated throughout the entire stride phase. During the first four years of life the foot is physiologically pronated and therefore does not require any treatment. If the foot continues to over-pronate after age of five, then bracing becomes necessary until approximately age 8; if over-pronation persists after this age or if bracing has not been instituted, surgery becomes the recommended treatment option. The ideal age range for treatment is between 8 and12 years of age. The clinical investigation should rule out the following conditions before recommending surgery: stiff flatfoot due to tarsal coalition, severe ligament laxity, neurological pathologies and outcomes of club foot. In collecting the patient’s history it is important to ask about occasional pain, unwillingness to walk long distances or early fatigue: all these signs are indicative of abnormal function. The two most obvious physical findings are a reduction of the plantar arch and a valgus deformity of the hindfoot. In severe cases, there may also be abduction and supination of the forefoot. Two tests are fundamental for an exhaustive examination of the foot: the Jack’s test, which consists in applying passive tension to the first metatarso-phalangeal joint and the tip toe standing test, where the patient is asked to stand on the tip of his/her toes. Both tests help to assess the correction of the calcaneal valgus deformity; as well, the patient will have problems standing on one foot. In studying the walking phase it is possible to identify early lift-off of the heel, a marked internal rotation of the tibia, the collapse of the plantar arch in the landing phase and a weak thrust phase. Surgical correction in adolescents involves the placement of an endorthesis in the sub-talar joint in order to reduce the over-pronation. The endorthesis may consist of implanting a resorbable device in the tarsal sinus or, alternatively, positioning a screw in the heel (calcaneo-stop surgery). Recently a new type of screw for the calcaneo-stop procedure was introduced. This device is made out of a resorbable material, Poly-L-lactic acid, which maintains its mechanical properties for about 12 months and is then resorbed over the following 5 years, therefore without needing to be explanted.
A small incision is made at the level of the tarsal sinus; the fibers of the sustentaculum tali (retinacular fibers) are then separated thereby exposing the tarsal sinus. The implant site is prepared using an awl at the calcaneal level, just in front of the subtalar joint; after tapping, a Hit Medica RSB calcaneo-stop screw is then positioned. If the foot does not achieve 90° dorsiflexion after surgery, percutaneus lengthening of the Achilles tendon should be performed. If only the screw has been implanted, the patient will be put in a walking leg cast for 2 weeks; if the heel cord has been lengthened, the leg cast should be worn for 5 weeks, of which the first 2 weeks without weight bearing. Upon removal of the cast, normal shoeing and physical activities like cycling and swimming are recommended.