Researchers optimise patient-specific bioresorbable implants with Additive Manufacturing
March 24, 2025
The Chair Digital Additive Production (DAP) at RWTH Aachen University, Germany, is researching the use of Additive Manufacturing in producing patient-specific bioresorbable implants in collaboration with project partners within the reACT (Resorbable solutions from the Aachen technology region) alliance.
Particularly in the case of critical size bone defects (e.g. long bones), the researchers anticipate that the combination of Additive Manufacturing, automated design configuration, and bioresorbable zinc-magnesium alloys can create implants with fewer side effects.
Bone defects caused by accidents, congenital malformations or tumour resection require complex reconstructive procedures. These procedures often result in a significant health burden for patients and high costs for healthcare systems. Permanent implants, such as titanium, can increase the risk of fracture due to stress shielding and often require follow-up surgery for removal. The development of innovative materials and design methods is, therefore, essential to improve both clinical and socio-economic outcomes.
Additive Manufacturing as a key technology
Within the reACT alliance, researchers are developing an algorithm-based design configurator for long bone defects. This tool automatically generates optimised implant designs based on patient-specific parameters such as defect geometry, age, bone density and weight. At the same time, the implant is also developed under the scope of Design for AM, focusing on Laser Beam Powder Bed Fusion (PBF-LB) and metallic materials such as zinc-magnesium alloys.
Automated patient-specific implant design
A design configurator is an algorithm that integrates logical, mathematical and geometric operations to generate an implant design that meets functional requirements. This design configurator methodology can also be adapted for other applications such as spinal cages and maxillofacial implants.
As the first step of the critical size bone defects investigation, segmented CT data of the defect site defines the geometric design space for the implant.
In the next step, adaptive lattice structures are generated within the design space to ensure uniform resorption of the implant. By varying the geometry arrangement, new tissue growth is encouraged and degradation products can be efficiently removed. In addition, the implant structure is tailored to the patient-specific biomechanical loads in an effort to minimise the risk of refracture.
Optimal material properties
Zinc and magnesium alloys are considered promising materials for resorbable bone implants. While pure zinc (Zn) has favourable degradation properties, it lacks the mechanical strength required for use in implants. Magnesium (Mg), on the other hand, is already used in orthopaedic implants due to its bone-like mechanical properties, but it degrades too quickly in certain applications, and gas formation can occur in moist tissue environments.
At extensive alloy screening of different compositions, ranging from pure zinc to Zn8Mg alloys, identified a ZnMg alloy with ≤1 wt% magnesium as the optimal composition for bone replacement applications.
First demonstrator
A first demonstrator implant has already been successfully manufactured by Additive Manufacturing. The implant design was customised to the specific defect size and bone structure of the patient, generating a cylindrical design space. Various lattice structure geometries were automatically incorporated into this space. These geometries can already be adjusted in terms of arrangement, unit cell size and strut diameter.
Project Partners in the reACT Alliance (Vertical 3) include:
- Meotec GmbH
- Medical Magnesium GmbH
- Fibrothelium GmbH
- University Hospital Aachen
- Fraunhofer Institute for Laser Technology (ILT)
- RWTH Aachen – Chair Digital Additive Production (DAP)
The reACT alliance is part of the RUBIN (Regional Entrepreneurial Alliances for Innovation) programme, funded by the German Federal Ministry of Education and Research (BMBF).
