The repair of complex fractures and significant bone loss It remains one of the greatest challenges in modern traumatology. Current methods work, but they don't always achieve a perfect fit to the bone defect, lengthen procedures, and are not without complications.
In that context, an international group of researchers has presented a proposal that, simply put, allows “print bone” in full operationUsing a modified glue gun, surgeons can create three-dimensional grafts directly onto the damaged bone, layer by layer, in a matter of minutes.
From traditional grafts to in situ bone impression
For decades, the repair of extensive bone defects has relied on autologous grafts, donor bone or metal implantsEach option has its own drawbacks: a second surgery to obtain the graft from the patient, limited availability of donors, immunological risk, and problems with anatomical adaptation.
The irruption of 3D printing in medicine It opened the door to customized parts, designed from scans and medical images. However, manufacturing a custom implant requires laborious preliminary processes: image acquisition, digital modeling, printing, post-processing, and, in many cases, manual adjustments in the operating room.
That whole circuit involves long times, high costs, and a certain margin of error when the bone defect is very irregular. In clinical practice, this means that many European hospitals cannot routinely deploy such sophisticated solutions to all patients who would need them.
The new approach fundamentally changes the focus: instead of adapting the bone to a pre-made implant, The implant is molded directly onto the injured bone., with the surgeon directing the process in real time inside the operating room.
A portable tool based on a glue gun
The device, developed by specialists from Korea University School of Medicine, Sungkyunkwan University, and MITIt stems from a simple idea: transforming a hot glue gun into a high-precision surgical tool capable of extruding a biocompatible filament.
This compact system is hand-operated, allowing the surgeon control the direction, angle, and depth of the print on the bone defect. Instead of a volumetric 3D printer located away from the operating table, the “printer” is integrated directly into the surgical instruments.
The key lies in the filament used. The researchers have designed a mixture of polycaprolactone (PCL) and hydroxyapatite (HA)These two materials are widely studied in tissue engineering. PCL is a biodegradable thermoplastic with a relatively low melting point, around 60°C, which allows working at temperatures that do not damage surrounding tissues.
For its part, hydroxyapatite is a mineral naturally present in human bone, recognized for promoting osseointegration. By combining both components, the resulting filament acts as a “scaffold” that provides mechanical support while guiding the growth of new bone tissue.
Materials that adapt to bone and release drugs
One of the most interesting aspects of the development is the possibility of adjust the filament composition to modify its properties. By varying the ratio of hydroxyapatite and polycaprolactone, scientists can customize the hardness, elasticity, and load-bearing capacity of the graft.
This fine adjustment allows the material to be adapted to different areas of the skeleton or to different types of injury. It is not the same to reinforce a femoral diaphysis, subjected to high loads, as it is to fill a defect in a smaller bone or in a region with less mechanical demand.
In addition to its structural function, the printed scaffold incorporates a therapeutic dimension. The team has managed to integrate antibiotics such as vancomycin and gentamicin within the filament, so that the graft also acts as a local drug delivery system.
In laboratory tests, this material proved capable of inhibit the growth of common bacteria in post-surgical infectionssuch as Escherichia coli and Staphylococcus aureus. Thanks to the PCL and HA matrix, the antibiotics are released gradually over several weeks directly into the operated area.
This “localized medication” approach could reduce reliance on prolonged systemic antibiotic treatments, something relevant in hospitals in Spain and Europe where the fight against antimicrobial resistance It is a health priority.
Print the graft in minutes during surgery
In practice, the procedure is relatively straightforward: the surgeon inserts the filament into the handheld tool and, during the procedure, extrudes over the fracture or bone defectThe molten mass adapts to the irregularities, fills cavities, and begins to solidify rapidly.
According to the authors of the study, the entire process can be carried out in a matter of minutesThis is especially relevant in the operating room environment, where every minute counts to reduce anesthetic risks and operating costs.
Manual operation of the device adds a component of real-time customization This is difficult to achieve with prefabricated implants. The specialist can "draw" the graft based on what they see in the surgical field, making corrections as they go and adjusting the volume and density of the material where most needed.
This direct control opens the door to surgery that is more tailored to each patient, an aspect that fits with the growing trend towards Personalized medicine in European healthcare systemsInstead of relying on standard parts or complex pre-designed digital processes, the solution is generated on the fly within the operating room itself.
Another key element of the design is its programmed degradation. As the scaffolding is reabsorbed, the new bone is taking its placeso that, in the long term, what remains is not a permanent artificial structure, but the patient's own bone tissue.
Results in animals: more bone, stronger bone, and no infections
To validate the idea, the device was tested in a animal model with critically sized bone defectsThis type of injury does not regenerate spontaneously without intervention. The researchers chose severe femoral fractures in rabbits, a common model in bone regeneration studies.
These trials compared in-situ printing with the use of conventional bone cement, frequently used as a filling and fixation material. After 12 weeks of follow-up, the animals treated with the impression technique showed superior regeneration.
Histological and structural analyses did not detect no signs of infection or necrosis in the group treated with the new method. In addition, parameters such as the bone surface area formed, cortical thickness, and polar moment of inertia—related to mechanical resistance—were better than in the control group.
These results point to a more effective graft integration with the surrounding tissue already showing a more solid bone consolidation. The scaffold not only acted as temporary support, but also facilitated the regeneration of a bone with mechanical characteristics closer to the original.
Although these are still preclinical trials, the data serve as robust proof of concept and justify moving towards larger animal models and, in a later phase, towards human trials within regulatory frameworks such as the European one.
Regulatory challenges and potential impact in Europe
Despite the positive results, the leap from the laboratory to the hospital is not immediate. For such technology to reach operating rooms in Spain or elsewhere, further steps are needed. European Union countriesIt is necessary to pass several scientific and regulatory filters.
The project managers emphasize that it is necessary standardize manufacturing processes of the filament and the tool itself, validate sterilization methods and demonstrate that the system works with the same effectiveness and safety in larger animals, more comparable to humans.
Furthermore, the combination of medical device, implantable biomaterial and controlled drug release This places the technology in a complex regulatory environment, where it is likely to be assessed as a combination medical device. In Europe, this would mean complying with both the Medical Devices Regulation (MDR) and specific regulations on medicinal products.
If these stages are successfully completed, hospitals could have a tool that allows them to treat complex fractures, defects following bone tumors, or sequelae of severe trauma with faster solutions adapted to the patient's actual anatomy.
In healthcare systems like Spain's, where the pressure on traumatology and orthopedics is high, a technique that reduces surgical times, minimizes re-interventions, and reduce the risk of postoperative infections This could have a significant impact on both clinical outcomes and costs.
This new form of in situ bone 3D printing raises a paradigm shiftInstead of relying on implants manufactured before surgery, own operating room It becomes a "workshop" for personalized graftscapable of integrating with the bone, releasing antibiotics where needed and gradually disappearing as the tissue regenerates, an approach that, if it passes the next scientific and regulatory steps, could transform the way difficult fractures are addressed in hospitals in Spain and the rest of Europe.
