Madrid hospital implants personalized metamaterial bone prosthesis

The metal weighs 300 grams. Yet the personalized prosthesis implanted at Madrid's Gregorio Marañón Hospital can withstand more than 500 kilograms of load, according to the hospital's account. Nearly a year after surgery, the 38-year-old man treated for a high-grade tibia sarcoma has had no infection or related complications, kept his knee alignment and mobility, and can often walk without crutches.

The problem was not just a missing section of bone. An infection and a severe loss of bone density meant the tibia could not support a conventional implant, while available options could not remove the tumor and preserve knee mobility. The hospital's oncological surgeons therefore turned to UPAM3D, its Advanced Planning and 3D Manufacturing Unit, working with the Gregorio Marañón Health Research Institute and the Polytechnic University of Madrid.

The prosthesis uses a metamaterial structure: millimeter-scale rods arranged to recreate the form and function of bone. Instead of replacing the bone as a solid block, the lattice is designed to absorb mechanical loads and help prevent nearby bone from weakening through disuse. The team created a digital twin of the patient's healthy leg from radiological images, simulated forces generated by walking, climbing stairs and stumbling, then configured the internal lattice point by point. Fixation screws were aimed at the areas with the best bone quality.

During the operation, the team filled the titanium structure with cancellous, or spongy, bone from Gregorio Marañón's Bone and Osteotendinous Tissue Bank. The graft became interwoven with the metal, supporting bone integration and implant fixation. Follow-up imaging confirmed favorable adaptation, and the operation itself proceeded without complications.

So what changes in practice? For this patient, a device made inside a hospital was matched to his anatomy, the defect left by tumor treatment and the loads his leg needed to carry, rather than forcing a standard implant into an unsuitable bone. The case also fits Spain's broader move toward certified hospital manufacturing of customized devices, but the clinical evidence remains a single patient followed for almost a year; the hospital's reported outcome is encouraging, not yet a general result.