Research Career Scientist

Va Puget Sound Healthcare System, Seattle WA

Investigators

Linked publications & trials

Abstract

PROJECT SUMMARY (CURRENT RESEARCH AND GOALS) My research goals are to improve the mobility of Veterans with lower limb amputation, reduce their risk of injury, and enhance their comfort while wearing a prosthesis. I use randomized clinical trials to determine the efficacy of commercially available devices to guide clinical decision-making with evidence. If commercial devices fall short of expectations, I explore innovative approaches that could dramatically advance the state-of-the-art. Individuals with lower limb amputations sometimes see their mobility curtailed due to residual limb skin injuries. Infrequent, but high stresses from impact loads (e.g., jumping or fast walking) or torsion (e.g., rapid changes in direction) can certainly cause skin injuries, but so can repetitive insults from the thousands of steps taken each day. While clinicians have many commercially available prosthetic ankle-feet to choose from, none mimic the motion of the natural limb in all regards. To discover if a prosthesis with more natural motion would have better patient outcomes, I developed a torsionally adaptive prosthesis (TAP) that couples sagittal plane motion of the ankle (plantar- and dorsi-flexion) with transverse plane motion (external and internal rotation). Funded by a VA Merit Review, our recently concluded clinical trial found a 6:1 sagittal:transverse coupling ratio created a more natural motion and minimized residual limb torsion. Providing this coupling might improve mobility by allowing longer walking bouts without injury, but a mechatronic limb like the TAP would be unlikely to leave the lab. Striving for a commercially viable alternative, my team and I invented and patented the Pivot- Flex Foot, a passive prosthesis capable of 6:1 coupled motion. Using a validated finite element model, we are fabricating Pivot-Flex feet in different sizes and stiffness categories needed for an upcoming clinical trial. A more proximal challenge to mobility is the clinical need for a well-fitting socket. Veterans who live near a clinic can be repeat customers until a satisfactory fit is obtained, but about a quarter of all Veterans live in rural communities far from VA Medical Centers. I am testing inexpensive digital scanning technology to remotely capture a Veteran’s residual limb shape with the assistance of a caregiver or helper. My VA funded research will determine if prosthetic sockets, made in part with remote study helper assistance, fit at least as well as prosthetic sockets made entirely with in-person prosthetic services. Affordable advances in technology that improve access to care and service delivery are clinically welcome. Of course, a well-fitting socket is essential for mobility, but perspiration can quickly bring mobility to a halt due to adherence problems. New to market are perforated liners that allow perspiration to seep away from the skin. I am conducting a nationwide, decentralized clinical trial (n=180) to compare three clinically available products intended to address problems of perspiration. The results are expected to identify the product that maximizes stability, suspension, and comfort when activities and/or environmental conditions induce perspiration. Lastly, a fan of science fiction movies might think biomechatronic limbs are soon to be within our reach. My team and I have developed several microcomputer operated limbs with machine and deep learning algorithms to predict movement intentions. One particularly intriguing problem we are exploring is how to respond to rapid changes in loads such as when a person picks up or sets down a heavy item. However, in the short-term, clinicians need more pragmatic studies. My team has recently completed a load carriage study intended to provide recommendations on how an individual should carry a load (anteriorly, posteriorly, on the prosthetic limb side, or on the intact limb side) and which of several different study feet are best for such activities. The knowledge disseminated from my research will provide evidence to assist clinicians with their prescription practice and guide the commercial development of new products. I expect both to lead to substantial quality of life improvements for Veterans with lower limb amputation.