Rationale for a Modified Crutch Use Methodology for Individuals With Weak or Paralyzed Hip Abductor Muscles
Individuals with weak or paralyzed hip abductors may make use of two methods to reduce pathological gait kinematics as a result of their disability; reducing the need for the hip abductors or developing an equivalent torque on the body. Compensatory motions such as torso tilting or hip hiking “balance” the body reducing the need for the torque that would be developed by the hip abductors. A contralateral crutch develops a body torque that is equivalent to that developed by the hip abductors. Individuals with weak or paralyzed hip abductors intuitively adopt a wide crutch stance, contrary to the prescribed method where the crutches are vertical in the frontal plane. Using a wide stance angle in the frontal plane is hypothesized to improve gait with weak or paralyzed hip abductors more so than when using crutches in the traditional manner. Crutches develop a torque on the body that is equivalent to what would be developed by the hip abductors while standing still. A wide stance angle increases the moment arm that the crutch force acts through while standing still, increasing the torque developed, potentially increasing the positive effect of the crutch which may reduce the need for compensatory motions. However, a similar effect has not been characterized during gait. The hypothesis is that a wide crutch stance angle improves a gait with paralyzed hip abductors more so than a crutch used vertically in the frontal plane. The assumption is that this is accomplished by decreasing energy expenditure and/or reducing the need for compensatory motions more so than a crutch used vertically in the frontal plane. A three-dimensional dynamic model is used to test the hypothesis. The model predicts that excessive pelvis depression and decreased pelvic rotation result when the hip abductors are paralyzed. Compensatory motions, hip hiking and torso tilting, and crutch use are shown to decrease the prevalence of pathological kinematics. Crutch use with a wide stance angle improves gait kinematics more than a vertical crutch with the same body weight supported on it. This study provides evidence that the need for compensatory motions and the prevalence of pathological gait kinematics may be reduced when using a wide crutch stance angle compared to a vertical crutch stance angle.