The needs of lower limb amputees go beyond meeting the bare minimum requirements of daily living. Quality of life issues, such as the ability to engage in active sports and recreation, are vitally important. In fact, the inability to run was most frequently cited as the most important unmet need of such amputees in a survey conducted by Dr. Ernest M. Burgess and colleagues in the late 1970s. Burgess is a Seattle orthopedic surgeon and former UW faculty member who founded a nonprofit research laboratory called Prosthetics Research Study in 1962.
That finding prompted Burgess in 1980 to initiate a study of how successfully unilateral amputees could actually run. In collaboration with Doris Miller and Roger Enoka of the UW kinesiology department, Burgess carried out a study of the motion of amputees running in order to determine the characteristics of their movements and the particular difficulties they face in trying to run using a prosthetic device. Out of that effort has come the Seattle Foot, a specially-engineered prosthesis that allows lower limb amputees to run and engage in active movements.
The Seattle Foot, introduced in 1985, was the first step, so to speak, in the development of a complete Seattle Limb system. The Foot itself is worn by over 120,000 amputees worldwide. The invention received a Presidential Design Achievement Award in 1984 and the Washington Governor's Award for New Products in 1990.
To improve running performance, the Foot uses a patented spring, called a monolithic keel, made of a strong and lightweight material called Delrin®, a DuPont product. The spring helps the patient push off in taking a step. It does so by storing energy when the foot initially steps down, and then releasing that energy at the ball of the foot when the heel leaves the ground as the step is completed. The result is a more natural, springy step than is possible with a conventional prosthetic. Over the keel is crafted a cosmetic or plain foot to suit the amputee's preference.
The pioneering design has spurred further developments to aid amputees. "The research leading to the design and increased performance of the Seattle Foot has influenced the development of entire lower limb prosthetic systems," says Burgess. The increased functional response provided by the Foot has encouraged the creation of many similar devices for other limbs. "Amputees wearing these dynamic response limbs enjoy greater functional capacity and comfort," he notes.
Development of the Seattle Foot, which is fabricated by Model & Instrument Works, Inc., in Seattle, has been a team effort. Burgess notes that "engineering consultants were recruited from the large, locally available aerospace industry," to help in the project.1 The first foot prototype was made of layered fiberglass. Over a period of about two and a half years, the team worked on refinements, with support of Veterans Administration Rehabilitation Research and Development Funds, leading to the device introduced in 1985 that incorporated the Delrin keel. Performance of the Foot was evaluated in a national study coordinated by James Reswick and staff in the Rehabilitation Research and Development Section of the Veterans Administration Central Office in Washington, D. C..