The Functional Importance of Powered Wrist Flexion for Transradial Prosthetic Users
Abstract
Objective and Rationale Loss of an arm causes profound difficulty in performing everyday tasks such as eating or dressing. Although using an artificial arm, or prosthesis, is the best treatment, it is hard to replace all the movements that the intact hand and arm can make. Many people use a myoelectric prosthesis, which means that it is controlled by electrical signals generated by contraction of muscles on their residual limb. People with an amputation through the forearm (transradial amputations) need a prosthetic hand and a prosthetic wrist. Most currently available myoelectric hands are simple devices that only open and close, but more sophisticated hands have recently been developed that provide several different types of grasp, although controlling them is harder. The only currently available myoelectric wrists provide rotation but cannot flex (bend forwards) or extend (bend backwards); this makes it hard for users to position their hand correctly, so they often have to move their shoulders or body to perform a task. These unnatural movements, called compensatory movements, make using a prosthesis awkward and slow, and can result in injuries over time. Recently, another research group has shown that a simple, open/close hand combined with a wrist that can rotate, flex, and extend is as useful as pairing an intact hand with a wrist that only allows rotation. In other words, a more useful wrist makes even a simple hand work better. Importantly, a wrist that can bend and flex as well as rotate may help people perform tasks without having to make unnatural compensatory movements and allow people to use the new prosthetic hands more effectively. At the Center for Bionic Medicine (CBM), within the Shirley Ryan AbilityLab, we have developed a wrist (the CBM wrist) that can both rotate and bend backwards/forwards, and we have developed a new, easier way of controlling prosthetic devices, called pattern recognition (PR). Our collaborators at the University of Alberta, Canada, have developed a new way to measure compensatory movements using cameras and eye-tracking devices to record movement and gaze. Using this technique allows us to see how different combinations of simple and sophisticated prosthetic hands and wrists affect compensatory movements. The objective of our study is to compare body movements during task performance while using four different types of prosthesis: a simple open/close hand or a multi-movement hand, combined with wrists that allow rotation only, or rotation and bending. The rationale is that we will find out which different hand/wrist combinations allow people to use their prosthesis more naturally, making it easier to accomplish tasks and reducing the risk of future injuries. This information will also help clinicians to choose the best prosthesis parts for their patients and help us in our goal of making the CBM wrist commercially available to Service personnel and civilians with arm loss. Impact of the Study The results of this study will help people with amputations at the below-elbow forearm level who use a myoelectric prosthesis. The information we will get can be used by clinicians to help them chose which hands and wrists to prescribe. For example, a wrist with rotation and bending combined with a multi-grasp hand may allow people to perform tasks more similarly to people without amputations. Or we may find that having a more functional wrist is more important than a multi-grasp hand for reducing compensatory movements. These findings will help clinicians prescribe prosthetic components that will maximize function while minimizing cost. This information will also help clinicians and their patients obtain reimbursement for expensive prosthetic parts, if they are shown to be better that less expensive options. Most people with arm amputations are young and typically want to return to an active life, including work. For military Service members, this may
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910863
Entities
People
- Laura A Miller
Organizations
- Shirley Ryan AbilityLab
- United States Army