Repairing a broken bone remains a medical challenge when fractures are irregular or extensive. Classic bone transplants often require tissue taken elsewhere or metal implants, at the cost of complications and long preparation. Researchers from Sungkyunkwan University in South Korea, in collaboration with the team of Jeong Joon Jeon, offer an unexpected alternative: a modified glue pistol capable of printing directly on the lesion a material imitating the bone.
Understand the limits of current bone transplants
Treating a severe fracture is not limited to fixing the bone with a metal plate. When a significant loss of bone matter occurs, surgeons must fill the void with a transplant. These interventions are still largely based on two solutions. Either we take bone from the patient, or we use a donor. In both cases, the constraints are heavy. Sampling surgery generates a second wound, painful and susceptible to complications. As for grafts from donors, they are accompanied by risks of rejection and supply limits.
In recent years, 3D printing has opened up new perspectives. Producing a personalized transplant from medical images is possible. However, the operation requires time, specialized software and meticulous planning. In a complex fracture, surgeons do not have this period in the operating room. Standard implants do not always marry the irregular bone contours. The result can compromise alignment, slow down healing and weaken consolidation.
To get around these limits, the South Korean researchers therefore chose another path. They made the bone substitute directly during the operation, as close as possible to the fracture. Their idea: to transform a simple glue gun into a surgical tool. Thanks to this device, the transplant is no longer prepared upstream, but printed in real time, exactly adapted to the shape of the bone defect. This technical choice upsets traditional logic. Instead of adapting the bone to the implant, it is the implant that immediately adapts to the injured bone.
The biomedical device and its innovative composition
The heart of technology lies in a filament designed specifically to be extruded by a modified thermal pistol. Unlike plastic polymers used in classic 3D printing, the formulation combines two carefully chosen materials. On the one hand, polycaprolactone (PCL), a biodegradable polymer already used in regenerative medicine, capable of softening to 60 ° C. This relatively low temperature reduces the risk of tissue burns during surgical application. On the other hand, hydroxyapatitis (ha), a mineral which naturally constitutes the bone matrix and promotes regeneration.
The proportion between PCL and HA can be adjusted as required. A mixer richer in hydroxyapatitis offers greater rigidity, adapted to areas supporting strong mechanical constraints. Conversely, a higher PCL content guarantees more flexibility, useful for marrying irregular forms. The device thus retains great anatomical versatility, an essential quality in the face of the diversity of fractures.
© Jeon et al., 2025
The pistol itself is not an improvised gadget. The researchers modified it to ensure precise manual control of extrusion. The operator can adjust the angle, depth and thickness of printing in real time, which makes the surgical procedure adaptable to each case. “” Our system allows a faithful anatomical correspondence. Without going through heavy stages of modeling and preoperative cutting “Said Jung Seung Lee in a press release. The filament is not content to provide a support structure. It was enriched in two antibiotics, vancomycin and genamicin, known for their effectiveness against frequent bacteria as Staphylococcus aureus And Escherichia coli. Their gradual release to the site of the operation limits postoperative infections, often feared in this type of interventions. This local strategy also reduces the side effects associated with systemic antibiotic.
Results of experimental tests on animal model
Before considering a clinical application, the team validated its concept on animal models. The experiments focused on laboratory rabbits, whose femoral bones have been voluntarily weakened to simulate severe fractures. Two groups were compared: one treaty with classic bone cement, the other with the material printed by the biomedical pistol. The two groups benefited from the same osteosynthesis system by plates and metallic screws, in order to stabilize fractures.
Observations over twelve weeks have revealed net differences. In animals having received printed transplant, the formation of new bone tissue was faster and denser. The measurements carried out showed significant gains on the bone surface, in cortical thickness and in mechanical solidity. In parallel, no sign of infection or necrosis has been observed. At the end of the follow -up period, around 10 % of the implanted material had already deteriorated. Which started its replacement with the neoflemed bone.
Histological analyzes have confirmed this biological integration. Unlike cement, which remains an inert mass, the printed matrix favored colonization by bone cells. “” The graft has been designed to gradually degrade and be replaced by functional bone tissue “, Underlines Jung Seung Lee. These results show that technology does not only act as a mechanical filling, but as a regeneration catalyst.
Clinical perspectives and challenges to be met for this innovative pistol
The idea of a tool printing bone transplants directly to the operating room seduced by its apparent simplicity. But its transition to clinical practice requires crossing several stages. First, the standardization of the production of the filament is essential. Each batch must guarantee constant quality, both mechanically and on the controlled release of antibiotics. Sterilization protocols must also be validated to meet international medical standards.
Antibacterial efficiency is another axis of improvement. Researchers plan to further optimize the concentration of integrated molecules in order to prolong protection against infections. This dimension is crucial, because infectious complications represent one of the main obstacles in complex bone surgeries. On the regulatory level, tests on large animals will be necessary to demonstrate the safety and efficiency of the pistol in conditions close to humans. These studies will also assess the solidity of the transplants printed in the face of the high mechanical stresses of certain joints. It is only after these validations that clinical trials can be considered.
If these steps are taken, technology could transform the care of severe trauma. The surgeon would have a compact and handy tool capable of creating a perfectly adjusted transplant in a few minutes. Without going through long modeling procedures. The time saving in the operating room and the best biological integration of the material constitute major assets. “” We believe that this approach may become a practical and immediate solution for bone repair », Projives Lee. But he recalls that only rigorous validation, in accordance with medical standards, will open the way to a large -scale clinical adoption.
Source: Jung Seung Lee et al., “In-Situ Printing of Biodegradable Implant for Healing Critical-Sized Bone Defect”, Device (2025).
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