Madrid Hospital Creates First 3D-Printed Bone Metamaterial Prosthesis, Saves Patient's Leg

A First in Personalized Bone Implants

Surgeons at Madrid's Gregorio Marañón Hospital have completed what they describe as the world's first personalized metamaterial bone prosthesis. The implant saved a 38-year-old patient from leg amputation after a tibial sarcoma destroyed much of the bone, and it was manufactured using 3D printing technology adapted from aerospace engineering.

The patient, Pierre Chazel, had already lost significant bone density to infection and could not support a conventional prosthesis. The medical team turned to engineers at the Polytechnic University of Madrid to design an implant that would not just fill the gap, but actually mimic the mechanical behavior of living bone.

How the Implant Works

Conventional prostheses replace bone with a solid piece of metal. This implant takes a different approach. Its internal structure is a network of millimeter-scale titanium rods arranged to distribute loads the same way natural bone tissue does. The design lets the patient's remaining bone grow into the lattice, which reduces the risk of rejection and helps the body accept the implant as part of itself.

The result is an implant that weighs barely 300 grams but can withstand more than 500 kilograms of load. A conventional titanium prosthesis of similar function typically weighs several kilograms and bears only 100 to 150 kilograms. The metamaterial structure achieves its strength through geometry rather than mass.

Surgical planning used a digital twin of the patient's healthy leg. Researchers simulated walking, climbing stairs, and stumbling to calculate the loads the tibia would face in everyday life. They then placed the screws in the areas with the best bone quality, which let the team plan the procedure with millimeter precision. Operating time was almost halved compared to conventional approaches.

What Comes Next

The hospital has already performed a second procedure with the same technology and is preparing two more personalized implants, one for a wrist and another for a sternum. The long-term goal is to bring hyper-personalized implants into the public health system, where each patient receives a device tailored to their own anatomy rather than fitted from standard sizes.

The metamaterial concept originated in aerospace, where weight and load distribution are critical. Transplanting that logic into orthopedic surgery is not entirely new, but this is the first time it has been used to replace a load-bearing long bone in a living patient. If the follow-up cases continue to succeed, the approach could change how surgeons think about bone cancer treatment, trauma reconstruction, and implant design in general.