Improved physical therapy for Achilles tendon injuries possible

UNIVERSITY PARK, Pa. — To enhance the recovery of patients with Achilles tendon injuries, Daniel Humberto Cortes Correales, assistant professor of mechanical engineering at Penn State, received $600,000 from the National Institutes of Health (NIH).

Ruptures of the Achilles tendon, located on the back of the calf connected to the heel bone, are common and often have long term negative effects. In particular, the muscle can atrophy, or grow weaker from not being used, while the patient recovers. With this grant, Cortes will explore the use of neuromuscular electrical stimulation (NMES) for surgically treated ruptures to enhance patient outcomes. 

NMES is a therapy that delivers painless electrical impulses to nerves, causing the muscle to contract. This contraction simulates the effect of walking without as much strain and helps to keep the muscle from atrophying. Combined with physical therapy, it can be used to “re-train” a muscle to build strength after an injury. 

“We developed some ultrasound methods that measure the mechanical properties of the tendon, so we know how strong it is at different points in the healing process,” he said. “Based on those numbers, we can determine how much electrical stimulation can be applied to the muscle to activate it, while not reinjuring the tendon.”

Cortes explained that using NMES to keep the muscle active could provide more precise control, rather than relying on vague guidelines prescribed by physicians. For example, patients are often advised to begin putting a percentage of their body weight on their leg for a certain period of time. 

“The problem with that is the loading of the injured leg will vary a lot from person to person. Some patients may do less because they are afraid of reinjury or some will do more,” he said. “But with NMES, we have a better way of controlling how much force is applied to the tendon. I think we will have more uniform results and all patients could experience a better outcome.”

As an engineer, Cortes will be leading the project through his expertise on mechanical properties.

“If we use too much stimulation, we can reinjure the tendon. If we don’t use enough, it may not slow down the atrophy of the muscle,” he said. “So, evaluating the strength and mechanical properties of the tendon itself is needed to optimize the treatment.” 

The first phase of the project will continue to gather data and model the mechanical strength of the tendon. With research team members Dr. Robert Gallo, associate professor in the Department of Orthopaedics, Dr. Christy French, associate professor in the Department of Radiology, and Karin Silbernagel from the University of Delaware, the second phase will begin clinical trials. 

As the team explores the use of NMES, Cortes hopes it could help all patients with these injuries get back on their feet more quickly and safely. 

“The ultimate goal is to make these stimulations procedures standard for the rehabilitation from Achilles tendon ruptures,” he said.