Madrid Hospital Saves a Leg With the First 3D-Printed Titanium Metamaterial Prosthesis

At Gregorio Marañón University General Hospital in Madrid, a 38-year-old man named Pierre went from facing amputation to walking without crutches, thanks to a 300-gram piece of 3D-printed titanium that does not behave like a normal implant. It behaves like bone.

The patient

Pierre had a high-grade bone sarcoma in his tibia. After an infection destroyed much of the bone density, his leg could no longer support a conventional prosthesis. The medical team had to choose between amputation and a custom solution. They chose the latter.

The hospital's Advanced Planning and 3D Manufacturing Unit, UPAM3D, worked with engineers from the Polytechnic University of Madrid to design the implant. Using radiological images, they built a digital twin of Pierre's healthy leg, then simulated the loads the tibia would face during walking, climbing stairs, and stumbling. That data dictated the internal geometry of the implant.

The metamaterial structure

The prosthesis is not a solid rod. It is a lattice of millimeter-scale titanium bars arranged to distribute mechanical load the way healthy bone does. The structure weighs 300 grams yet withstands more than 500 kilograms in simulation. A conventional titanium prosthesis of similar function typically weighs several kilograms and supports 100 to 150 kilograms. The metamaterial approach inverts the usual trade-off between weight and strength.

The design also allowed the surgical team to place fixation screws in the strongest remaining bone areas. During the operation, the implant was filled with cancellous bone from the hospital's own tissue bank. The graft wove through the metal lattice, helping the patient's own bone grow into the prosthesis rather than simply sitting next to it.

Results

Nearly a year after surgery, Pierre has no infections or complications. His knee alignment and mobility are stable. He can walk, often without crutches. He suffered a fall during recovery that fractured his other leg; the implant survived intact.

The hospital has already completed a second procedure using the same approach. Two more implants are in development: one for a wrist, another for a sternum.

Why this matters

Gregorio Marañón is not the first hospital to 3D-print a custom implant. What makes this case different is the metamaterial architecture and the in-house certification path. Spanish public hospitals are moving 3D printing from experimental support to certified manufacturing activity. UPAM3D operates under ISO 13485:2018, the same standard used for commercial medical devices. That matters because it means the hospital can legally manufacture patient-specific devices at scale, not just as one-off exceptions.

The cost comparison is also striking. A comparable commercial prosthesis can cost between 30,000 and 50,000 euros. The 3D-printed version cost about 3,000 euros, which is essentially the price of the raw titanium and machine time. The hospital frames the saving as secondary to access: if personalized implants are affordable within a public health system, more patients can receive them.

The path forward

The hospital's goal is to offer hyper-personalized medicine as a routine option in the public system. That will require standardizing the digital workflow from scan to design to print, and convincing regulators that lattice structures and in-house manufacturing are as safe as traditional prostheses. The clinical results so far suggest the technology can meet that bar.