After years of hard work, Dr. Sandra Shultz, director of UNC Greensboro’s Center for Women’s Health and Wellness in the School of Health and Human Sciences, will earn a patent from the U.S. government for a device she and her colleagues developed. The device, a GMetric3D Knee Joint Laxity Testing Apparatus, helps reduce the number of ACL (anterior cruciate ligament) injuries, particularly among female athletes. 

When Shultz, who is trained in kinesiology, worked as a certified athletic trainer for women in the 1990s, she saw what she describes as “a rash” of ACL injuries. She saw so many, in fact, that she got “really good at rehabilitating them.” 

But when she returned to school for a doctoral degree in sports medicine, she wanted to learn how to prevent these injuries. A completely torn ACL will not heal without surgery and requires months of rehabilitation. 

“When you’re out for a year for recovery,” she says, “you lose an entire season.” 

Understanding risk factors for ACL injury in women 

Shultz first explored the many risk factors for ACL injury – often a complete tear in the ligament, causing the knee to collapse. In particular, she wanted to know why females are more prone to the injury than males.  

“Most women and adolescent girls have greater laxity, or looseness, of the ligaments that stabilize the knee – a common risk factor for ACL injury,” she says. 

Simply put, too much laxity makes it more difficult to stabilize the knee during sports maneuvers like cutting and landing. Unlike the hip, the knee is not a deep ball and socket joint, it relies on ligaments for stability and guidance. 

Digging deeper, Shultz – who also co-directs the Applied Neuromechanics Research Lab in the Department of Kinesiology – saw a correlation with female sex hormones. ACL ligaments loosen in the same sense that ligaments loosen to enable childbirth.  

“We see acute changes in knee laxity across the menstrual cycle when estrogen is elevated, which in turn can impact how the knee moves during sport maneuvers,” she says. 

In addition, she found that females have smaller and structurally weaker ligaments and less muscle mass than males.  

“Like a rubber band, a thinner one can stretch farther than a thicker one,” she says, which in part explains a female’s greater laxity. 

Designing a solution 

To address it, Shultz realized that identifying females with increased laxity could be a predictor for ACL vulnerability. She decided to design a mechanism for quantifying the condition. Working closely with her colleague, Dr. Randy Schmitz, Shultz developed the GMetric3D Knee Joint Laxity Testing Apparatus. The device measures the laxity of knee joint ligaments to screen for those who have a greater-than-average risk of injury, diagnose an injury, and monitor the healing of the ligament post-surgery. 

To use the device, the patient’s thigh sits in a cradle, remaining stable, while the lower leg is moved to measure anterior translation, rotation, and side-to-side movement, assessing the ligaments of the knee.  

Supported by several grants from the National Science Foundation and the North Carolina Biotechnology Center, Shultz and Schmitz tested and refined the device over five years, working to successfully earn a patent that will be issued officially in April this year. 

To file the applications, she worked with Dr. Michael Marshall of Innovate UNCG, the university’s technology transfer office. “Sandy’s approach will give clinicians a lot more information and a more precise measurement than was possible with previous devices,” he says. 

“We have a prototype and are seeking funding to develop a more commercial-ready model, which would connect to a computer to measure and graph the results of the laxity tests,” she says.  

Though the device is not yet ready for the market, Shultz is optimistic about the next phase of development. She will retire from the University in June but plans to continue with research and product development. The patent ensures Shultz has 20 years to pursue commercial applications without competition. 

With a patent for the GMetric3D Knee Joint Laxity Testing Apparatus, and the drive and resilience it took to earn it, Shultz may soon give female athletes a leg up on preventing ACL injuries. 

Story by Mary Daily 
Images courtesy of Sandra Shultz