A low-dimensional sagittal-plane forward-dynamic model for asymmetric gait and its application to study the gait of transtibial prosthesis users.

This paper presents an extension of a recently developed low-dimensional modeling approach for normal human gait to the modeling of asymmetric gait. The asymmetric model is applied to analyze the gait dynamics of a transtibial prosthesis user, specifically the changes in joint torque and joint power costs that occur with variations in sagittal-plane alignment of the prosthesis, mass distribution of the prosthesis, and roll-over shape of the prosthetic foot being used. The model predicts an increase in cost with addition of mass and a more distal location of the mass, as well as the existence of an alignment at which the costs are minimized. The model's predictions also suggest guidelines for the selection of prosthetic feet and suitable alignments. The results agree with clinical observations and results of other gait studies reported in the literature. The model can be a useful analytical tool for more informed design and selection of prosthetic components, and provides a basis for making the alignment process systematic.

Low-dimensional sagittal plane model of normal human walking.

This paper applies a robotics-inspired approach to derive a low-dimensional forward-dynamic hybrid model of human walking in the sagittal plane. The low-dimensional model is derived as a subdynamic of a higher-dimensional anthropomorphic hybrid model. The hybrid model is composed of models for single support (SS) and double support (DS), with the transition from SS to DS modeled by a rigid impact to account for the impact at heel-contact. The transition from DS to SS occurs in a continuous manner. Existing gait data are used to specify, via parametrization, the low-dimensional model that is developed. The primary result is a one-degree-of-freedom model that is an exact subdynamic of the higher-dimensional anthropomorphic model and describes the dynamics of walking. The stability properties of the model are evaluated using the method of Poincare. The low-dimensional model is validated using the measured human gait data. The validation demonstrates the observed stability of the measured gait.

Disadvantaged families with HIV infection: a challenge in health care delivery.

Perinatally transmitted HIV infection is a devastating and growing problem among families who are often the most disadvantaged units in society. However, being disadvantaged does not necessarily mean that the family is dysfunctional and unable to cope creatively with a child and other family members who are HIV infected. A model is presented which allows the nurse to assess both strengths and stressors of families having perinatally transmitted HIV infection. Characteristics of HIV infected families who cope well, and those who cope less well are delineated. Eight broad principles of management for these families are discussed and their application illustrated with two case studies.