Prosthetic Components and Stability in Amputee Gait

US Department of Veterans Affairs12 enrolled

Overview

The biomechanics of changing direction while walking has been largely neglected despite its relevancy to functional mobility. In addition, an increased risk of injury can be associated with turning due to a decrease in stability. The objective of this study is to understand the biomechanics of turning gait in sample populations of intact and trans-tibial amputees and the capacity of prosthetic components to facilitate transverse plane movement. The clinical impact of this investigation is the development of interventions that increase functional mobility, stability and safety while turning. The researchers propose to investigate three sets of hypotheses. The first set addresses the fundamental biomechanical mechanisms associated with walking along a circular trajectory, how intact subjects differ from amputees, and the effect of a rotation adaptor pylon. The second set of hypotheses addresses dynamic stability and the potential influence of prosthetic interventions. The third set of hypotheses addresses how the rotational properties of the prosthetic pylon can influence comfort and mobility during daily activities.

Most of what is known about how amputees walk and how the properties of prosthetic components affect their gait has been discovered through sagittal plane observations while amputees walk back and forth along a straight line. Abnormal limb loading, thought to be a principal factor in the occurrence of residual limb pain which in turn may cause instability and limit mobility, can certainly occur while walking in a straight line. However, the incidence of abnormal limb loading is likely amplified when performing more complex gait activities, such as turning or avoiding obstacles; activities that are so very common in everyday life. The specific aims of this investigation are to: 1. discover the biomechanical strategies used and the stability of both intact individuals and trans-tibial amputees walking along a circular trajectory and 2. explore the effects of a prosthetic intervention on turning biomechanics, stability, comfort, and mobility. We propose to investigate three sets of hypotheses: The first set of hypotheses addresses the fundamental biomechanical mechanisms associated with walking along a circular trajectory, how intact subjects differ from amputees, and the effect of a rotation adaptor pylon. We will conduct experiments to test three hypotheses related to achieving a change of heading, orientation, and balancing of centripetal forces necessary to walk along a circular trajectory. The second set of hypotheses seeks to identify whether trans-tibial amputees with a rigid pylon are more unstable during a turning task than non-amputees and whether or not the rotation adaptors enhance stability. We will conduct experiments to calculate an index of dynamic stability that measures the rate at which a person can respond to a perturbation and return to a stable gait pattern. The third set of hypotheses addresses how the rotational properties of the prosthetic pylon can influence comfort and mobility during daily activities. To measure comfort and mobility, we will solicit questionnaire responses and step count measures from amputees after a one-month period of wearing a rigid pylon and after a one-month period of wearing a transverse plane rotation adaptor (within-subject comparison). In addition to these field measurements, we will also compare the distance traveled during a six-minute walk. Patient opinions about their prosthesis and mobility measures over long periods of time can play a significant role in prosthesis evaluation. For veteran amputees who experience discomfort and increased risk for residual limb skin problems, it seems reasonable to suppose that these problems might occur when walking along a curved trajectory rather than just a straight line. The joint forces and moments of turning may differ significantly from those exhibited while walking in a straight line. The proposed research will create a new knowledge base with which to understand prosthetic intervention effectiveness. The immediate clinical impact for the trans-tibial amputee is the determination if transverse plane rotational adapter pylons can improve their comfort, mobility, and stability.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 70 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Amputee Subjects: * be a unilateral trans-tibial amputee between the ages of 18 and 70, * weigh 220 pounds or less, * have been fit with a prosthesis and using a prosthesis for at least two years, * wear the prosthesis for at least 8 hours per day, * walk without crutches or a walker, * able to walk outside the home and in the community, * have not fallin within the last six months, * Non-amputee subjects participating in this investigation will meet similar inclusion criteria except for those related to prosthesis use. Exclusion Criteria: * Amputee Subjects: * amputation due to tumor, have an active tumor, or are undergoing treatment of a tumor, * have pain in legs or any condition that interferes with walking. * Non-amputee subjects participating in this investigation will meet similar exclusion criteria except for those related to cause of amputation.

Outcomes

Primary Outcomes

Local Dynamic Stability (Hip During Straight Walking)

Maximum finite-time Lyapunov exponents were used to estimate the local dynamic stability of the amputee's sagittal plane hip, knee and ankle angles for their prosthetic limb with and without the torsion adapter while walking straight, while turning with the prosthesis on the inside of the turn, and while turning with the prosthesis on the outside of the turn. Maximum finite-time Lyapunov exponents measure the rate of kinematic separation of a gait cycle trajectory perturbed by naturally occurring disturbances and neuromuscular control errors. A positive exponent indicates divergence of a system, with increasing values indicating a les stable system.