Forces Produced by Ground Contact Rotational Orthotic Devices

Abstract

The correction of lower extremity rotational deformities, such as tibial and femoral torsion, requires the application of derotational forces. One method of applying such rotational forces during ambulation is through the use of ground contact rotational orthotic devices. Two devices were tested. One device uses parallel rows of slanted rubber ribs and the other has slanted rubber ribs located in a circular array to produce rotational forces when the device strikes the ground during normal walking. It was found that the parallel rowed rib produced a rotation of 5.5 deg during walking and when rotation was prevented, torsional force produced by the device was approximately 20 in-lb. The circular array of ribs produced a complete rotation of 18 deg. When rotation was prevented, the heel produced 21.5 in-lb of torsion. The possible resisting torsion of a normal adult male was determined to be 11 in-lb at an 80 lb applied weight. Therefore it is concluded that the ground contact rotational devices will either provide rotation to the extent of the applied load or will apply torsional force greater than that encountered by normal leg structure.