In total, 39 children (average age, 10.3 years) diagnosed with flexible flat foot were enrolled. Exclusion criteria included fixed-foot deformity, a previous surgical history, congenital or developmental foot disease, and neuromuscular diseases, such as cerebral palsy. They were evaluated by more than three consecutive radiological studies and by RCSP measurements. Radiological parameters used to evaluate the alignment of both feet included the anteroposterior talocalcaneal angle (APTCA), lateral talocalcaneal angle (LTTCA), lateral talometatarsal angle (LTTMA), and calcaneal pitch (CP). Two rehabilitation medicine physicians recorded the measurements.
RCSP was determined in the following manner. First, subjects lay prone on a bed parallel to the floor. Regardless of the calcaneal fat pad, the upper, middle, and lower bisection points of calcaneus were marked and three points were connected to create a centerline. Then, the subjects stood in a relaxed bipedal stance with their feet apart as wide as an adult's fist. We measured the angle between the centerline of the calcaneus and the vertical line to the ground.
An anteroposterior, lateral weight-bearing radiograph was then obtained for each foot. On the anteroposterior radiograph, one indicator was measured to describe the hind foot alignment. On the lateral radiograph, three indicators were measured to demonstrate the medial longitudinal arch.
Flat foot was defined when either of the feet had >4° valgus of RCSP angle and one abnormal radiological finding greater than 30° in APTCA, 45° in LTTCA, 4° in LTTMA, or less than 20° of CP. The APTCA is the acute angle between the dichotomous line of the calcaneus and talus with the long axis on an anteroposterior radiograph. The LTTCA is the acute angle between the dichotomous line of the calcaneus and talus with the long axis on a lateral radiograph. The LTTMA is the acute angle between the longitudinal axis of the first metatarsus and talus on a lateral radiograph. The CP is the acute angle between the inferior border of the calcaneus and the baseline on a lateral radiograph. The baseline was defined as the connection of the closest point of the first metatarsus and calcaneus on the floor (Fig. 1 ).
A cast was produced for each subject, from which a pair of RFOs was manufactured (Biomechanics, Goyang, Korea) on the basis of the inverted technique. The orthosis inverts the rear foot and pronates the fore foot through the subtalar joint and longitudinal axis of the midtarsal joint. A 5° inversion can correct 1° RCSP in the pronated position. RFOs were produced from a positive cast of the feet, which captured the foot position with the subtalar joint in a neutral position. Each subject was recommended to wear the orthoses for more than 8 hours per day, and to walk with heel strike at initial contact and reciprocal arm swing to normalize the gait pattern. The examination was performed three times: on the first visit, at 12-18 months after application of RFO, and at 24 months after RFOs were provided.
RCSP was determined in the following manner. First, subjects lay prone on a bed parallel to the floor. Regardless of the calcaneal fat pad, the upper, middle, and lower bisection points of calcaneus were marked and three points were connected to create a centerline. Then, the subjects stood in a relaxed bipedal stance with their feet apart as wide as an adult's fist. We measured the angle between the centerline of the calcaneus and the vertical line to the ground.
An anteroposterior, lateral weight-bearing radiograph was then obtained for each foot. On the anteroposterior radiograph, one indicator was measured to describe the hind foot alignment. On the lateral radiograph, three indicators were measured to demonstrate the medial longitudinal arch.
Flat foot was defined when either of the feet had >4° valgus of RCSP angle and one abnormal radiological finding greater than 30° in APTCA, 45° in LTTCA, 4° in LTTMA, or less than 20° of CP. The APTCA is the acute angle between the dichotomous line of the calcaneus and talus with the long axis on an anteroposterior radiograph. The LTTCA is the acute angle between the dichotomous line of the calcaneus and talus with the long axis on a lateral radiograph. The LTTMA is the acute angle between the longitudinal axis of the first metatarsus and talus on a lateral radiograph. The CP is the acute angle between the inferior border of the calcaneus and the baseline on a lateral radiograph. The baseline was defined as the connection of the closest point of the first metatarsus and calcaneus on the floor (
A cast was produced for each subject, from which a pair of RFOs was manufactured (Biomechanics, Goyang, Korea) on the basis of the inverted technique. The orthosis inverts the rear foot and pronates the fore foot through the subtalar joint and longitudinal axis of the midtarsal joint. A 5° inversion can correct 1° RCSP in the pronated position. RFOs were produced from a positive cast of the feet, which captured the foot position with the subtalar joint in a neutral position. Each subject was recommended to wear the orthoses for more than 8 hours per day, and to walk with heel strike at initial contact and reciprocal arm swing to normalize the gait pattern. The examination was performed three times: on the first visit, at 12-18 months after application of RFO, and at 24 months after RFOs were provided.
