Assessment of human ambulatory dynamic postural stability: Analysis and comparison of butterfly curve

Total hip/knee joint replacement patients tend to suffer limited motor control in their lower limbs due to unhealed, open wound. As a result, physicians often recommend patients who underwent surgery to utilize walker as aid in walking training that helps to balance the dynamic weight bearing balance, in order to speed up improving the lower limbs' motoring function. Nevertheless, there is a dire need in establishing a comprehensive set of mols and methods by which quantitative evaluation can be given to study the patients' dynamic weight bearing and walking stability in terms of how patients can be clinically evaluated for the need' to prescribe walking aid treatment or when it is safe enough for them to move freely without the aid of a walker. In this paper, the dynamic foot pressure (weight bearing) from normal subject and total hip/total knee replacement patient groups during ambulation were collected and compared. The dynamic foot pressure data were collected using a home-made portable foot pressure sensing system. The sway pattern of center of pressure (COP) was displayed as a butterfly curve and used for weight bearing symmetricity assessment. Five quantitative indices were derived from butterfly curve for comparison. The results indicate that the symmetricity of butterfly curve of the normal subject group is better than the patient groups. In addition, the patient group often surgery with walking aided is better than the patient group before surgery. It also demonstrates that the total knee replacement patient group is better than that of the total hip replacement patient group. Finally, three different height setting strategies (i.e. greater trochanter height, distal wrist crease height, and the average height of previous two) of walker's handle were tested for postural stability. The results indicate that distal wrist crease height for walker's handle setting is the best strategy for the patient to regain dynamic postural stability.