Theories of human ambulation with applications to swing-through crutch gait

Previous studies have observed that the orientation of the trunk is often maintained in a fixed attitude with respect to the crutch/arm segment during the early part of crutch stance in “swing-through” crutch gait. We hypothesized that trunk control, described as a “hold-and-swing” mechanism, could serve to help propel forward movement of the ambulator. Like the child's playground swing, we believe that crutch users can “pump” via control of one segment with respect to another. Three different models were developed to assess this technique. The data from these models support the hold-and-swing technique as a propulsive mechanism for swing-through crutch gait.; Other locomotion models represent the foot as a rocker. Rockers have been used for crutches, but design parameters have not previously been theoretically based. Experiments were performed to evaluate rocker radii based on specific ambulation models. Rockers did not affect the gait parameters as significantly as expected; however, offsetting the feet, one slightly in front of the other to increase the effective foot rocker length, did appear to be a promising technique to allow a smoother transfer from crutch to body stance.; Like the models previously described, all models have assumptions and limitations that must be considered. Inverse dynamics, widely used in clinical gait labs, uses a rigid link model of the lower limb to calculate the torques and forces required to produce observed motions. Results from analysis of a specific prosthetic polycentric knee joint found significant errors when these prosthetic components are assumed to correspond to the models of a standard gait analysis system. Other issues regarding the use of inverse dynamics in gait analysis (bi-articular muscles, co-contraction, and validation) are also discussed.; Yet, while models do have inherent limitations and assumptions, knowledge can be gained from their application to human ambulation and specifically swing-through crutch gait. Models were used to test and evaluate the effect of rocker modification and the propulsive role of the hold-and-swing mechanism. These results may help to improve orthotic management and influence physical therapy treatment of those who use this type of ambulation.