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Release: Nov. 26, 2002

UI orthopaedic surgeons to receive national award

Several decades of research leading to important improvements in total hip replacements have earned a University of Iowa professor of orthopaedic surgery and biomedical engineering and his colleagues the Orthopaedic Research and Education Foundation (OREF) Clinical Research Award from the American Academy of Orthopaedic Surgeons (AAOS).

John Callaghan, M.D., the Dr. Lawrence and Marilyn Dorr Endowed Chair for Hip Reconstruction and Research, will be presented with the award and $20,000 at the AAOS annual meeting in February 2003.

The award, which was established in 1994, recognizes outstanding clinical research related directly to musculoskeletal disease or injury. It is one of four awards for orthopaedic research presented annually at the Kappa Delta Awards ceremony.

"We are honored to receive this very prestigious award," Callaghan said. "The UI's Department of Orthopaedic Surgery has a long tradition of receiving both the OREF award and Kappa Delta awards and we are proud to continue that tradition."

Callaghan will share the award with his UI colleagues, Douglas Pedersen, Ph.D., research scientist in orthopaedic surgery, Richard Johnston, M.D., professor of orthopaedic surgery, and Thomas Brown, Ph.D., the Richard and Janice Johnston Chair in Orthopaedic Biomechanics and professor of engineering and biomechanical engineering, for their work on the clinical biomechanics of wear in total hip replacement.

Callaghan and his colleagues contributed to the important discovery that wear at the bearing surface between the artificial ball and socket is the most important factor determining long-term durability of hip replacements. The researchers followed 4,000 hip replacement patients over a span of 30 years and used a unique combination of clinical studies and biomechanical models to identify causes of hip replacement failure.

"Our studies have shown that at 30 years, about 30 percent of patients have had a failure and many times the failure is related to wear of the bearing surface," Callaghan said. "As we saw the problems, we developed models to explain the failure modes."

Wear of the bearing surface produces small particles, which cause a biologic response of bone resorption (a process known as osteolysis). Osteolysis is a major cause of hip replacement failure.

The UI researchers were the first to show that wear is related to how much the ball of the artificial hip has to slide across the socket. They also discovered that the debris can get into the joint and cause accelerated wear. In addition, models developed by the researchers showed that contact between the socket's cup corner and the neck of the ball can cause high stresses and failure.

"Through this accumulated knowledge we have learned to redesign hip replacement components," Callaghan said. "Surgeons now use as small a head size as possible and we try to eliminate anything in the system that will cause third-body particulate debris. Manufacturers have also redesigned the head-neck junctions to prevent impingement on the cup corners."

The novel biomechanical models and techniques developed during this work also are useful tools for evaluating new bearing surface designs.

"This recognition of research excellence is richly deserved," said Joseph A. Buckwalter, M.D., UI professor and head of orthopaedic surgery, and a researcher and staff physician at the Iowa City Veterans Affairs Medical Center. "Dr. Callaghan has earned international renown for his expertise in hip and knee surgery and for his critical contributions to research and education. This award appropriately recognizes the work of Dr. Callaghan and his colleagues that forms the foundation for improvements in total hip replacement that will benefit millions of people with severe hip arthritis."

Callaghan earned his medical degree from Loyola Medical School and received his bachelor's degree from Notre Dame University, majoring in science and engineering. After completing his residency in orthopaedics at the UI, Callaghan moved to New York for a year to undertake two fellowships, one in orthopaedic surgery at Memorial Sloan-Kettering Cancer Center and one in hip surgery at the Hospital for Special Surgery. Callaghan also was a faculty member at Duke University before returning to the UI as an associate professor of orthopaedic surgery in 1990. He was promoted to professor in 1993. Callaghan also is a researcher and staff physician at the Iowa City Veterans Affairs Medical Center.

Stuart Weinstein, M.D., UI professor and the Ignacio V. Ponseti Chair in Orthopaedics, won the OREF Clinical Research Award in 1998. Members of the UI Department of Orthopaedic Surgery also have received Kappa Delta awards in 1956,1971,1972,1980, 1982 and 1986. For more information on the AAOS's Kappa Delta/ OREF Clinical Research Awards visit http://www.aaos.org/wordhtml/research/comittee/research/rsrch_6.htm

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