$7 3D Printed Femur Models Could Revolutionize Surgery

A 3D printed femur costing just $7 could soon change how surgeons prepare for complex bone surgeries and tackle bone tumors. This vision is now closer to reality, thanks to a breakthrough by surgeons from the University of Texas Southwestern Medical Center (UT Southwestern) in collaboration with researchers at the University of Texas at Dallas (UTD), who have developed a 3D printed femur that could transform how doctors prepare for bone surgeries.

The team’s 3D printed replica of a human femur was made to mimic the structure and density of real bone. Built from an affordable, biodegradable material, this model gives surgeons a realistic way to practice procedures, opening new possibilities for personalized surgical preparation.

Researchers constructed and tested 3D printed femurs using polylactic acid: The top bone is a 3D printed humerus (upper arm) and the bottom bone is one of the 3D femurs. Each femur bone costs about $7 to produce. Image courtesy of UT Southwestern.

One of the greatest challenges for surgeons when planning bone surgeries is understanding the unique geometry and properties of each patient’s bones. Traditionally, doctors have used cadaver bones or synthetic models in biomechanical studies to understand how bones react to implants, surgical techniques, and injuries. These models help surgeons practice procedures and test implants, but they are expensive, difficult to come by, and lack customization to match a patient’s unique anatomy, limiting their use in personalized surgical planning.

To solve this issue, UT Southwestern orthopedic oncology surgeon Robert Weinschenk and hand and upper extremity surgeon Richard Samade (who run a 3D printing lab) reached out to Wei Li, a 3D printing expert and Assistant Professor of Mechanical Engineering at UT Dallas’s Erik Jonsson School of Engineering and Computer Science. Their goal was to collaborate on creating a faster, cheaper alternative for orthopedic biomechanical studies, a project that began two years ago.

Dr. Wei Li evaluates a 3D printed femur replica in the lab. Image courtesy of the University of Texas at Dallas.

“The femur is a focal point of biomechanical research because of its critical role in weight-bearing and mobility,” said Weinschenk, who is also an Assistant Professor of Orthopaedic Surgery and Biomedical Engineering at UT Southwestern. “The use of 3D printing to generate humanlike bones can be a significant boost to researchers studying new surgical techniques and conditions such as osteoporosis, traumatic fractures, deformities, and benign or malignant bone lesions.”

The team used polylactic acid (PLA)—an inexpensive, biodegradable polyester commonly used in 3D printing—to construct various femur models with different attributes, such as wall thickness and infill density. They then tested the 3D printed models to assess flexural strength using three-point bending, comparing their performance to human femurs.

Mechanical engineering doctoral student Kishore Mysore Nagaraja (left) and Dr. Wei Li tested the properties of the 3D printed femur replicas in the lab. Image courtesy of the University of Texas at Dallas.

Developing a prototype that could realistically replicate the performance of a human femur was a complex task. Working at UT Dalla’s Comprehensive Advanced Manufacturing Lab, Li and mechanical engineering doctoral student Kishore Mysore Nagaraja identified the best methodology for creating a replica that closely mimics the biomechanical response of an actual femur. Using settings of 5% infill density, two to four wall layers, and a resolution of 200 micrometers provided the optimal flexural strength. Increasing the infill to 20% with six wall layers allowed the model to further approximate the strength and flexibility of real femurs, making it an effective, low-cost alternative for biomechanical studies.

“To make plans for surgery, surgeons need to know the geometry of the bone. With 3D printing, we’re able to print out the femur bone sample with the same geometry of the femur inside the body,” said Li.

Dr. Weinschenk’s 3D printing lab in the Green Research Building uses 3D printers to develop the femur samples, including this Ultimaker S3. Image courtesy of UT Southwestern.

The final design, representing the femur’s midsection, measures nearly eight inches long and one inch in diameter,  a scaled replica of the femur’s strongest load-bearing area. The femur is the longest and strongest bone in the human body, with an average adult femur reaching about 18 inches.

Constructed from PLA, the replica performed comparably to human bone in lab tests, making it a promising candidate for further surgical research and training applications. This precise replication allows doctors to practice surgeries with unmatched accuracy, potentially reducing operation times and improving patient outcomes. These findings were detailed in a study published in the Journal of Orthopaedic Research.

Researchers test a 3D printed femur design in a universal testing machine, which measures a variety of properties. Image courtesy of the University of Texas at Dallas.

At just $7 per model, these 3D printed femurs are much cheaper alternatives to traditional synthetic bones, which can cost anywhere from $220 to $300 each. For comparison, cadaver bones, when available, come at an even higher price due to preservation and handling requirements. For example, a disarticulated shoulder or knee specimen can range from $500 to $600, but human cadaveric tissue only allows a limited number of training sessions as tissue quality deteriorates over time.

Considering these limitations, 3D printed bones offer a much better solution to surgical training. These replicas could save a lot of money and be much more accessible for hospitals and medical programs without compromising the quality needed for realistic practice.

“Four generations of synthetic femur models have been developed for biomechanical testing and sold commercially since 1987,” explained Weinschenk. However, they have had limitations, including cost and delivery time. He said the 3D printing technique he and his colleagues created solves those problems. “We think this is novel and can gain wide use and acceptance because anyone with a cheap 3D printer can download the file, print the specimen, and do their own studies in an inexpensive way without delay.”

Robert Weinschenk, M.D. (left) and Richard Samade, M.D., Ph.D. (right). Image courtesy of UT Southwestern.

Meanwhile, Samada notes that using a 3D printer to create biomechanically realistic models removes a major barrier to research and opens the door to clinical applications: “For example, a surgeon could print bones with patient-specific pathologies and use those models to develop personalized treatment protocols. It’s a major step forward in engineering surgical solutions for patients with difficult bone pathologies, with a focus on preservation of limb and function.”

With patients now living longer, surgeons emphasize the need to develop lasting, innovative treatments. This study sets the stage for future work, with plans to expand 3D design protocols to cover a wider range of bones.

Looking ahead, the team envisions these models playing a role beyond surgical preparation. They could be used to simulate various medical scenarios, from testing new implant designs to evaluating treatments for bone diseases. For instance, printing models with tumors could allow doctors to test therapies and predict outcomes in a controlled environment, making treatments safer and more effective.

Also, the polylactic acid material used in the 3D printed femur has potential for bone repair. As a biodegradable polymer, it may be a cheaper, more sustainable alternative to titanium and other metals currently used in orthopedic implants. Li says that one day, these types of custom implants could be printed for individual patients, offering a better fit and reducing the chance of complications.