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Research / Discovery

Bioengineer develops wireless sensor to track healing of difficult to treat bone fractures

May 20, 2010
By Lana Hoff

Christian Puttlitz, associate professor of mechanical engineering and a faculty member in the School of Biomedical Engineering, is providing physicians with the tools they need to determine if early healing is occurring properly in difficult to treat bone fractures.

Making sure bone is healing properly

Christian Puttlitz, associate professor of mechanical engineering, shows the new wireless sensor he has developed to assess whether bone is healing correctly.

Physicians treat more than 6 million bone fractures in the United States every year and about 10 percent of these fractures don’t heal properly. Multifragmentary or “comminuted” fractures, where the bone splits in several pieces, are especially difficult to treat and often require the implantation of screws and a plate to stabilize the healing bone.

During the early healing phase, the plate and screws protect the fracture site by taking on most of the loading at the site. As time goes on, the healing tissue starts to share more of the load.

The first three months is a critical time period when physicians closely monitor the patient to make sure the bone is healing properly. However, conventional X-rays cannot discriminate whether this is actually occurring.

Wireless monitoring system

Christian Puttlitz, associate professor of mechanical engineering and a faculty member in the School of Biomedical Engineering, is providing physicians with the tools they need to determine if early healing is occurring properly. Puttlitz came to Colorado State University in 2005 after working as a professor at the University of California, San Francisco while directing a biomechanics laboratory at San Francisco General Hospital. It was his experience at SFGH that motivated Puttlitz to try to design a wireless fracture monitoring system that ultimately would lead to better patient outcomes.

“My mission as a bioengineer is to have a positive impact on human health,” says Puttlitz. “If we can develop this technology to the point where patients with difficult fractures experience less pain and have fewer long-term complications, then I think we will have fulfilled this goal.”

More precise technique, better patient outcomes

Students work with Prof. Puttlitz on specimen preparation for biomechanical testing of human tissue in the Orthopaedic Bioengineering Research Laboratory at Colorado State.

Puttlitz and his collaborators have developed a new sensor that uses the changes in the load sharing between the implanted plate and healing tissue to assess whether the bone is healing correctly.

“The wireless sensor that we’re developing will provide physicians with a more precise technique to assess how the healing in complicated fractures is progressing,” says Puttlitz.

“By engineering newer designs, we have been able to optimize the sensor’s sensitivity and fully characterize its response to different forces.”

$900,000 NIH grant

A three-year, $900,000 grant from the National Institutes of Health was recently awarded to Puttlitz, principal investigator on the project, and Hilmi Volkan Demir, a physics and electrical engineering professor at Bilkent University in Ankara, Turkey. The investigative team also includes experts in human and veterinary orthopedic surgery. This grant enables them to continue exploring biomedical engineering applications of wireless radio-frequency microelectromechanical systems strain sensors.

As part of this novel study, they are developing and testing the use of telemetric sensors that have been shown to be a vast improvement over traditional radio-frequency structures.

Ready to start designing studies for human use

“Our laboratory data indicate that we can achieve the maximum level of sensitivity and accuracy across a broad range of frequencies,” notes Puttlitz. “We are ready to start designing studies for human use.”

Originally published in the College of Engineering Healing Health newsletter, Spring 2010.