Roughly one million total knee replacement procedures are performed each year in the U.S.
With sensors attached to her body, Lena Thompson cautiously climbs up one step, then a second and finally a third. Once at the top of a raised platform, she walks forward, stops, turns and descends the stairs—and repeats the exercise several times. Researchers from the William States Lee College of Engineering at UNC Charlotte observe Thompson, who recently underwent knee replacement surgery, as she performs the exercises as part of a project examining the effectiveness of knee implants.
Last year, Thompson, a retired daycare worker, visited the Biomechanics and Motion Analysis Lab directed by Nigel Zheng, a professor of mechanical engineering and engineering science who joined UNC Charlotte in 2008. She completed a number of exercises prior to surgery and had returned for post-surgery analysis.
As is the case with many patients, pain was the determining factor for Thompson as she considered knee replacement. “Excruciating” is how she described the agony she’d endured for the better part of a decade.
“I could hear the bones rubbing together when I walked; the pain was so bad I felt like falling to the floor,” she said. She tolerated the pain, undergoing periodic steroid injections to alleviate the discomfort.
Before surgery with OrthoCarolina, Thompson’s orthopedist mentioned that Zheng, a world-renowned authority on biomechanics, was seeking participants for a study related to knee implants. Through his work, Zheng has seen the positive impact of biomechanical research on the design of medical devices, prostheses and orthoses, exercise equipment, surgical instruments and other products.
“Mobility is very important to one’s life,” he said. “Patients with pain and limited mobility often lose hope of achieving a good quality of life. Our work has the potential to help people maintain their health, leading to greater productivity and efficiency in their everyday lives.”
Next Generation of Engineers
According to Zheng, those best suited to help solve complex, medical problems of the future are those he describes as “the next generation of engineers.” He takes seriously his role as a mentor, fostering a passion for this work in his students.
Junior Marc Duemmler has taken several courses taught by Zheng and now assists in his lab.
“In my Introduction to Solid Mechanics class, Dr. Zheng related the course material to biomedical engineering, and how he applied the material using real-life examples piqued my interest,” said Duemmler, who is majoring in mechanical engineering with a concentration in biomedical engineering. “I have taken his Orthopedic Biomechanics course, and I am currently enrolled in his Introduction to Biodynamics course. He always has an example of either his research or conducted by a researcher that he knows that is applicable to the concepts we are learning.”
In Zheng’s lab in Duke Centennial Hall, students like Duemmler gain practical experience, often conducting research with participants such as Lena Thompson. In the classroom, they propose study topics to tackle as teams.
“I teach through actual scenarios that have implications for human health,” said Zheng. “Critical thinking and problem solving—beyond mimicking what is done in class—are essential to students’ development as researchers. Learning to learn is vital, as today’s knowledge gives way to new knowledge. Engineers must be prepared to examine each problem for its unique features.”
Duemmler is appreciative of the chance to participate in hands-on research as an undergraduate.
“Getting to work with Dr. Zheng and his graduate students has given me first-hand experience that I think most undergraduate students will never experience. Just in the past year, I have gotten to learn so much about biomechanics just from conversations with him. I truly value the experience and knowledge that Dr. Zheng has, and I hope to learn as much as I can from him,” he said.
The Human Machine
UNC Charlotte’s location within the state's largest metropolis allows Zheng and his lab to collaborate with OrthoCarolina, Atrium Health and other health care providers and product manufacturers in the region.
“Our research often changes the way a medical problem is solved—from implant design, refinement of surgical tools and procedures, or post-surgery rehabilitation,” noted Zheng. “Relationships with the region’s leading health care providers allow us, for example, to offer insight related to medical image-based evidence of higher wear rates due to contact stress for metal-on-metal hip implants, fall risk assessments or the biomechanical evaluation of surgical techniques for ACL reconstruction.”
Currently, Zheng is gathering data related to knee joint function and pain levels prior to surgery and how different implants restore some functionality post-surgery.
“We ask questions such as, ‘Does the design meet the needs of some or all patients? Which features work for specific groups of patients?’” said Zheng. “As a biomechanics researcher, I study the body’s dynamic features and functions. Medical imaging makes that possible as it explores the structure of the human machine.”