Improving fit of artificial limbs.

Approximately 60,000 lower-limb amputations are performed in America each year. For the patient, the fit of a prosthetic device can define the quality of life. Yet, traditional methods frequently fail to provide the best possible fit. The same artificial leg that provides mobility and freedom can become the source of profound discomfort. For some, the poor fit may lead to painful pressure sores and troublesome, recurrent infections.

Modern imaging technology holds promise for these problems. Researchers at Washington University School of Medicine in St. Louis, Mo., are applying innovative technologies to rehabilitation science and using sophisticated imaging machines to enable comprehensive evaluations of prosthesis fit. According to a team of scientists from the university's Mallinckrodt Institute of Radiology, three-dimensional imaging techniques are superior to the traditional plaster-casting methods used to outfit amputees with artificial lower limbs.

Traditional socket fitting for a lower-extremity prosthesis begins with plaster-cast replication of the residual limb, followed by a sequence of manual modifications called rectification. The outcome of the process largely is dependent on the skill and craftsmanship of a prosthetist. Michael W. Vannier, now head of the Department of Radiology, University of lowa, lowa City, indicates that is a wide margin for error.

The standard plaster-casting technique provides a rigid, static copy of the limb in one set position. With just a rock-hard cast, it is impossible to address the shape changes of bone and tissue that occur while an amputee walks with the prosthesis. Just as the skin and soft tissue on the bottom of your foot are molded and shaped in a snug pair of shoes, the shape of the residual limb changes while compressed in a prosthesis. As a patient walks, pressure points on the limb vary...