Technique for the measurement of hindfoot inversion and eversion and its use to study a normal population

Following earlier work identifying the difficulties of defining the subtalar neutral position, the authors have developed new techniques to measure the ranges of inversion and eversion in normal subjects. A test rig has been designed and constructed to apply a known torque about an anterior posterior axis and an electrogoniometer has been used to measure the resulting movements. The neutral position was defined as that position corresponding to the footplate being horizontal and the leg vertical. In a study of 100 normal subjects (50 female/50 male), it has been shown that the average overall range of motion decreased from 53.2 ° in 20-year-olds to 44.3 ° in 60-year-olds. It was also demonstrated that females had a greater range of motion than males, but that this difference reduced with age. This fact was largely accounted for by a decrease in the range of eversion in female subjects.