Compensation for Weak Hip Abductors in Gait Assisted by a Novel Crutch-Like Device

Abstract

A novel crutch-like device compensates for weak hip abductors in gait. Many teenagers with weak hip abductors, an important group being individuals with low level spina bifida, who are able to walk with crutches, abandon community ambulation in favor of a wheelchair because walking takes more energy than using a wheelchair. The health benefits to standing and walking as opposed to using a wheelchair include improved bone growth, improved blood circulation, reduced bladder infections, reduced pressure sores and prevention of contractures. The increased energy cost, which is characterized by excessive motions of the pelvis and torso, is attributed to weakened or paralyzed hip abductor muscles. A novel crutch, designed by the authors, lowers the energy cost of walking which encourages patients with weak hip abductors to continue ambulation.

Published research shows that significant work is done in the frontal plane by the hip to stabilize the pelvis in normal gait. In the absence of hip abductors, other motions and muscles are used to inefficiently stabilize the pelvis. The new crutch compensates for weak or absent hip abductor torques by applying a load on the side of the upper torso. A 3D model of crutch walking validates the device and determines the forcing and fitment guidelines. The novel 3D gait model is capable of capturing crutch gait incorporating pelvic tilt, pelvic rotation and pelvic obliquity.

The 3D model predicts a reduction in the hip abductor moment required during a gait cycle when using the crutch compared to forearm crutches if the user has very weak hip abductor muscles. The decrease in the required hip abductor moment is attributed to the forcing caused by the crutch, which may reduce excessive lateral displacement of the pelvis and torso. The decrease in the required hip abductor moment reduces the compensating motions that would otherwise be necessary.