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Release: Oct. 24, 2002

Photo: Nicole M. Grosland, left; Brian D. Adams

New total wrist replacement device created at UI Orthopaedic Biomechanics Laboratory

University of Iowa Health Care researchers, working with San Diego-based biotechnology company Kinetikos Medical, Inc. (KMI), have developed a new total wrist prosthesis for patients with severe wrist arthritis. The Universal 2 total wrist system, developed by Brian D. Adams, M.D., professor of orthopaedic surgery, and Nicole M. Grosland, Ph.D., assistant professor of biomedical engineering and orthopaedic surgery, was designed at the UI Orthopaedic Biomechanics Laboratory.

Although attempts at total wrist replacement have historically been fraught with complications, early indications are that the Universal 2's unique design, which closely mimics the normal wrist anatomy, will overcome past obstacles. The prosthesis, which uses the same materials and some of the same mechanical concepts as in total hip and total knee replacement, is engineered for both performance and longevity.

"The best patient for the Universal 2 prosthesis is an individual with severe wrist arthritis who is not routinely involved in activities that place high demands on the hand and wrist," said Adams, who performs between 15 and 20 wrist replacements per year.

Since the Universal 2 device was cleared to market by the FDA earlier this year, approximately 30 of the new prostheses have been implanted.

"The long-term prognosis for these patients is excellent for both function and durability," Adams said.

Each phase of development of the Universal 2 included both laboratory testing and computer modeling. This work was completed in the UI Orthopaedic Biomechanics Lab, which has been actively involved in research of the hand and wrist and the development of implants since the 1960s. The research team consists of faculty and professional engineers who work collaboratively with faculty orthopaedic surgeons.

"The computer model allowed information to be gathered that is not readily available through experimental testing alone," Grosland said. "For example, the model depicted how the components move relative to each other, how loads transfer through the prosthesis and into the surrounding bone, and how the materials may deform under high stress."

Laboratory experiments were used to test motion at the articulating surfaces to determine the strength of the connections between the plastic and metal parts and to assess the durability of the metal stems that fix into the bone.

Adams and his colleagues evaluated other wrist replacement devices in developing their new design.

"Our first goal was to improve the shapes of the articulating surfaces. By changing these shapes, stresses on bone and the prosthesis, as well as the risk of dislocation, were greatly reduced," he said.

Additional enhancements in the Universal 2 include the option to implant the prosthesis without cement when indicated by the physician, preservation of more bone, an offset position of the prosthesis within the bone to increase wrist motion and power, and precise instrumentation for accurate insertion of the prosthesis.

University of Iowa Health Care describes the partnership between the UI Roy J. and Lucille A. Carver College of Medicine and UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide. Visit UI Health Care online at www.uihealthcare.com.