Researchers print bone grafts in-situ

A joint research team from Sungkyunkwan University and Korea University, along with the Massachusetts Institute of Technology (MIT), has created customized bone implants that can be directly extracted for patients’ fracture or defect areas using a device similar to a glue gun that melts plastic adhesive. The results of this study were published in the international journal Devices. It has been proven safe and effective in rabbit experiments and is expected to expand into clinical trials involving humans in the future.

Previously, when bones were damaged, metal prosthetics or donated bones were transplanted. Recently, three-dimensional bone tissues have also been created using 3D printers. However, if the fracture area was irregular or complex, pre-scan, modeling, and manufacturing processes were essential for custom implants. This increases time and expense, and decreases surgical efficiency. Donated bones also carried risks of infection or immune rejection.

Professor Lee Jeong-seung of the Department of Global Biomedical Engineering at Sungkyunkwan University, who led this study, noted, “I got the research idea from the opinions of actual doctors.” The doctors mentioned that even if implants are made in advance using 3D printing, upon opening up during surgery, they often do not fit well with the defect area, necessitating additional processing.

The research team devised a device that prints implants directly at the surgical site. The material is a filament mixed with hydroxyapatite (HA), which aids in bone regeneration, and polycaprolactone (PCL), a plastic that safely decomposes in the body.

PCL melts at only 60 degrees Celsius, allowing it to be used safely during surgery without damaging surrounding tissues. Moreover, the melted PCL can flow into the gaps of the bone, filling irregularly broken areas without any gaps. By adjusting the HA ratio of the filament, its hardness and strength can also be modified according to the situation.

The research team stated that a doctor can hold the implant printing device like a glue gun and stack the material in the desired direction and depth to fit the shape of the broken bone within minutes. This allows for the creation of perfectly fitted custom bone implants without complex CT (computer tomography) or modeling and processing procedures.

The research team also added infection prevention features. They incorporated antibiotic components vancomycin and gentamicin into the filament to enable gradual release for several weeks after surgery. Consequently, the risk of infection around the bone was significantly reduced, while also lowering the risks of side effects and resistance compared to taking or injecting antibiotics.

Applying this technology to fractures in the femur (thigh bone) of rabbits resulted in rapid regeneration of the bone without infection or tissue necrosis within 12 weeks. The research team explained, “It outperformed existing bone cements in key metrics such as bone surface area and strength,” adding that “the printed bone substitute gradually decomposes over time, allowing new bone to naturally fill the space.”

“We can create and apply bone implants in real-time in the operating room, which can shorten surgical time and increase accuracy,” said Professor Lee. “We plan to expand the range of applications by adding various functionalities in the future.” However, he noted that tests on large animals like pigs and humans are needed for commercialization.