University of Texas at Dallas mechanical engineers have designed a 3D-printed femur that could help doctors prepare for surgeries to repair bones and develop treatments for bone tumors.

The engineers, who worked in collaboration with UT Southwestern Medical Center orthopedic surgeons, published their first study on the 3D-printed thighbone online Aug. 5 in the Journal of Orthopaedic Research.

The study, which focused on the middle section of the bone, establishes 3D-printing parameters for a femur for use in biomechanical testing. Researchers said more studies will be needed before the technology could be available for widespread use.

To study and validate innovative surgical implants and techniques, surgeons perform biomechanical studies using donated cadavers or commercially available synthetic bones, which help them determine optimal surgical fixation and predict the response of the bone. Synthetic bones, also used in surgical training, can be expensive, take time to acquire and lack the ability for patient-specific solutions.

UT Southwestern researchers approached Dr. Wei Li, a UT Dallas expert in 3D-printing technology, two years ago to collaborate on a less costly and faster alternative for orthopedic biomechanical studies.

"To make plans for surgery, surgeons need to know the geometry of the bone," said Li, assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science and corresponding author of the recent study. "With 3D printing, we're able to print out the femur bone sample with the same geometry of the femur inside the body."

Through trial and error, UTD mechanical engineering doctoral student Kishore Mysore Nagaraja developed many iterations of the femur. Mysore Nagaraja, who works in Li's Comprehensive Advanced Manufacturing Lab, performed a series of tests on each artificial bone to measure mechanical performance and material properties to make the samples as similar as possible to real femurs.

"This collaborative experience is the best thing a student could ask for," said Mysore Nagaraja, who is expected to graduate in December. "To get an evaluation of my testing research directly from the doctors who are going to use it is a very good validation of our research."

The bone replica is made of polylactic acid, a bio-based, low-cost biodegradable polymer commonly used in 3D printing. The design, which represents the midsection of the femur, is almost 8 inches long and nearly 1 inch in diameter. In biomechanical tests, it performed as well as a human femur. Researchers estimated each 3D-printed femur cost $7 to make.

Li said 3D-printed bones have a range of potential applications. The polymer, for example, might replace other materials used in bone repair, such as titanium. Li said researchers also could print tumors onto 3D-printed bones and test treatments on the printed samples, or the replicas might be used to help grow human bone tissue.

"With 3D printing, we're able to print out the femur bone sample with the same geometry of the femur inside the body."

Dr. Wei Li, assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science

UT Southwestern researchers involved in the study included first author Dr. Robert Weinschenk, an orthopedic oncology surgeon, and Dr. Richard Samade, a hand and upper extremity surgeon, who run a 3D-printing lab. Both are assistant professors of orthopedic surgery with secondary appointments in biomedical engineering; Samade has a secondary appointment in plastic surgery.

"I reached out to Dr. Li and his team, and fortunately this has turned into an excellent collaboration between us," Weinschenk said. "With the knowledge and skill sets Dr. Samade and I have as surgeons - both with engineering backgrounds - in combination with Dr. Li's tremendous knowledge and expertise in mechanical testing and his amazing resources, our collaborative team is uniquely poised to try to tackle these types of challenges."

Additional authors were former UTD student Faiqa Alam BS'23, and Dr. Blaine Oldham, who graduated from UT Southwestern in May.