Madrid Hospital Saves a Patient's Leg With the World's First 3D-Printed Metamaterial Bone Implant

A surgical team at Madrid's Gregorio Marañón Hospital has performed what appears to be the world's first implantation of a fully personalized metamaterial bone prosthesis, saving a 38-year-old Frenchman's leg from amputation after a rare and aggressive tibia tumor.

The Patient

Pierre Chazel was diagnosed with a high-grade bone sarcoma in his tibia. By the time doctors identified the tumor, it had progressed far enough that the bone had suffered severe density loss from a prior infection. The tibia could no longer support a conventional implant. Standard treatment for this kind of presentation often ends in amputation. Instead, the surgical team at Gregorio Marañón chose to design a replacement from scratch.

How the Implant Works

The prosthesis was developed in collaboration with engineers from the Polytechnic University of Madrid (UPM). It uses a titanium metamaterial: a network of millimeter-scale titanium rods arranged to mimic the internal architecture of natural bone. The structure distributes mechanical loads the way real bone tissue does, rather than replacing the bone with a solid chunk of metal. That difference matters. A conventional titanium implant might weigh several kilograms and handle 100 to 150 kg of load. This metamaterial implant weighs roughly 300 grams and has been tested to support loads above 500 kg.

The design also allows the patient's own bone to grow into the implant over time, reducing rejection risk. The material was chosen specifically because it combines strength with the flexibility natural bone needs during everyday movement, including breathing and walking.

From Digital Twin to Surgery

To get the fit right, the team built a digital twin from Chazel's radiological images. They simulated the actual forces the tibia experiences during walking, climbing stairs, and stumbling, then used that data to configure the internal lattice point by point. The screw placements were directed toward areas with the best remaining bone quality. The operation took about two hours, and the incision was placed beneath the breast line to minimize visible scarring. Chazel was discharged within days and is walking again.

What Comes Next

The hospital has already completed a second procedure using the same approach. Two more implants are in development: one for a wrist and one for a sternum. The goal is to build a standardized protocol that can bring hyper-personalized implants into the public health system at scale. For now, the technology is expensive and labor-intensive, but the results suggest the approach is sound.