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Friday, March 2, 2001

Electronic knee implant gives in vivo information

Eight years of work has brought researchers and engineers at the Scripps Clinic, La Jolla, Calif., and three companies closer to the day when they can get in-vivo data on the forces that occur in the knee when people walk, climb stairs or get out of a chair. The data will come from an instrumented knee implant fitted with micro-transducers in the tibial tray combined with transmitters that allow researchers to get information of forces in four quadrants of the knee.

The clinical question of what loads are transmitted across the knee joint are very important to clinicians, as well as manufacturers of knee prostheses. Beverly Morris, RN, one of the principle exhibitors of scientific exhibit 19, said until recently scientists have utilized joint force data compiled by means of mathematical modeling and FEA platforms without reliable in-vivo verification. But advances in electronics technology may soon give scientists Clifford Colwell, MD, and Darryl D'Lima, MD, actual real-time data.

The miniaturization of computer chips, transducers and transmitters has opened a new door for telemetric implant research, similar to the telemetric hip prosthesis developed by Case Western Reserve University. Ten years ago, NK Biotechnology, Minneapolis, Minn., developed transducers that enabled researchers to get information on the ligaments and patella from a prosthesis implanted in cadaver knees.

The current project brings together the transducer technology of NK Biotechnology, the microelectronics technology of MicroStrain, Burlington, VT; the implant manufacturing skill of DePuy Johnson and Johnson; and the medical skill of Scripps Clinic.

The implantable electronic knee prosthesis has undergone rigorous testing to make sure there are no objectionable effects from the load cells and microprocessor. The transmitter will be remotely powered to transmit in all types of conditions and locations.

The device will transmit force data from the implant simulating what happens when an individual is performing activities of daily living. The prosthesis will be tested under conditions simulating 10 years of walking. "Researchers hope to place the knee implant in a patient next year," said Morris.

The objective is to improve patient care by having more accurate information about the functioning of a knee prostheses. It might lead to improvements in the design of implants, off-loading braces, assistive devices and even shoes. It might also lead to new ideas about rehabilitation after surgery.

In addition to Morris, coauthors of the study are Darryl D.D'Lima, MD, and Clifford W. Colwell, MD, both of Scripps Clinic, La Jolla, Calif.

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Last modified 02/March/2001 by IS