Imagine a surgeon fixing a shattered bone not with screws or plates, but with a device that looks like a craft-store glue gun. Instead of hot glue, it extrudes a custom mix of biodegradable plastic and minerals. These scaffolds fuse to broken bones, release antibiotics, and slowly dissolve as the body heals.

This new invention, known as a portable “in situ bone printer,” bypasses the months-long process of designing and fabricating bone implants outside the body.

“Our proposed technology offers a distinct approach by developing an in situ printing system that enables a real-time fabrication and application of a scaffold directly at the surgical site,” said Jung Seung Lee of Sungkyunkwan University in a press release.

Printing Bones on Demand

The device works by melting a biocompatible thermoplastic called polycaprolactone (PCL) mixed with hydroxyapatite (HA), a mineral that naturally occurs in bone. The mixture is loaded into the gun as solid sticks, heated to just above 60°C — cool enough to avoid damaging tissue — and extruded into fractures like molten bone paste.

By tweaking the ratio of PCL to HA, surgeons can change the hardness, flexibility, and degradation rate of the implant. Low HA makes the graft more adhesive. High HA boosts bone regrowth.

“This allows for highly accurate anatomical matching even in irregular or complex defects without the need for preoperative preparation such as imaging, modeling, and trimming processes,” said Lee.

The beauty of this approach lies in speed. Printing can take minutes, compared to hours or days for custom-made grafts. And the handheld design means a surgeon can tilt, angle, or layer the material however the fracture demands.

Fighting Infection While Healing

Implants often come with a deadly downside: infection. Up to one-third of open fractures develop bacterial infections, which can destroy bone and force the removal of implants. To counter that, the team embedded antibiotics, such as vancomycin and gentamicin, into their printable material.

Tests showed that the printed scaffolds released the drugs slowly over weeks. They inhibited E. coli and Staphylococcus aureus, bacteria that plague surgical patients.

“This localized delivery approach offers meaningful clinical advantages over systemic antibiotic administration,” Lee explained, noting that it could cut side effects and slow the rise of antibiotic resistance.

In their proof-of-concept trial, the researchers created severe femoral fractures in rabbits. Some animals received bone cement, a common but non-degradable filler. Others got the printed grafts. Twelve weeks later, the printed group showed stronger bone regrowth, denser tissue, and no infections.

Histological slides and micro-CT scans revealed that the scaffolds didn’t just hold the fracture together — they guided cells to rebuild new bone. The implants degraded slowly, making space for natural tissue to take over.

Still, the authors are cautious. They admit the scaffolds need improved adhesion, longer durability, and testing in larger animals before human trials. As they note in the paper, “Clinical adoption will require standardized manufacturing processes, validated sterilization protocols, and preclinical studies in large animal models to meet regulatory approval standards.”

The Future of Bone Repair

Bone injuries are among the most common traumas in medicine, and large defects often require donor grafts or metal prosthetics. Those options come with risks: rejection, poor fit, or stress fractures years later.

By contrast, this in situ printer promises something closer to science fiction: personalized, dissolving bone patches made on the spot. It’s a step toward operating rooms where 3D printing is not just a planning tool, but a surgical instrument.

As Lee puts it, the vision is clear: “We envision this approach becoming a practical and immediate solution for bone repair directly in the operating room.”

The findings appeared in the journal Device.