More mobility thanks to AI: customised finger joint implants from the 3D printer

Whether due to an accident during sport or the widespread disease rheumatoid arthritis: when finger joints become immobile, it is a serious limitation and a physical and psychological burden - for certain professions such as musicians, surgeons or craftsmen, it often even means the end of their career. In the future, a development by the Fraunhofer Research Institution for Additive Manufacturing Technologies IAPT, the Fraunhofer Institute for Ceramic Technologies and Systems IKTS, the Fraunhofer Institute for Toxicology and Experimental Chemistry IKTS and the Fraunhofer Institute for Toxicology and Experimental Chemistry IKTS could lead to the development of a new, more effective method of minimising the risk of infection;for Toxicology and Experimental Medicine ITEM, the Fraunhofer Institute for Mechanics of Materials IWM and the Fraunhofer Institute for Digital Medicine MEVIS to help fingers with destroyed or damaged joints regain their mobility.

Existing therapy for damaged finger joints
Today, if a finger joint loses its function due to an accident or illness, the treatment methods are limited: in most cases, a stiffening procedure is performed, which severely impairs patients in their everyday lives. If an implant is to be inserted, there are currently two options on the market: Silicone implants, which in many cases quickly loosen again and have to be revised with a new procedure, or simply standard implants, which are only available in certain sizes and do not allow all movements. A custom-fit solution that does not slip and restores previous mobility - in other words, an individualised implant - should therefore be the goal of optimal patient care.

Project FingerKIt: Many innovations, one pioneering product
In the FingerKIt project, five Fraunhofer Institutes have now developed a concept that could make this possible: Individualised finger joint implants made of metallic or ceramic materials are to be manufactured quickly, safely and certified in an automated process chain. To this end, the scientists at Fraunhofer MEVIS first developed AI-supported software that is able to calculate three-dimensional models of the finger bones from two-dimensional X-ray images and correct any potential misalignment of the fingers. Researchers at Fraunhofer IAPT then derive the customised implant design from the finger model using AI and implement it in 3D printing. Since very fine and filigree structures have to be modelled, the scientists work with metal-binder jetting during production, i.e. the layered structure of the parts, which are sintered in a subsequent step, i.e. compacted and consolidated. At Fraunhofer IKTS, the implants are manufactured using near-net-shape manufacturing - another manufacturing process that produces products as close as possible to the desired final contour, so that only a few reworking steps are required. Ceramic materials are also used thanks to the expertise of Fraunhofer IKTS. These are processed in slip casting - a special plaster mould casting process. Fraunhofer ITEM is taking care of the issues relating to the biological compatibility and certification of the implants, while Fraunhofer IWM is simulating the mechanical loads.

The researchers have developed several innovations during their work on the project: »The AI-based calculation of a three-dimensional implant design from 2D templates such as X-ray images is completely new and is now patent-pending«, reveals Dr Arthur Seibel from the Component Design department at Fraunhofer IAPT. His colleague Dr Philipp Imgrund, Head of Process Qualification at the Fraunhofer IAPT, adds: "The process technology is also something special: because the structure of the implant shaft is very delicate, we have used metal-binder jetting for titanium as a 3D printing process. The process enables very precise production of the small, complex implants and at the same time allows the surface of the stem to be structured in such a way that it grows better into the bone. Furthermore, this allows us to minimise the reworking of the joint surfaces, which must be as smooth and low-friction as possible.

A new standard for treatment
The results of the FingerKIt project are good news for all patients who could not previously be helped satisfactorily. Thanks to the Fraunhofer innovations, even complicated cases - severely bent fingers, missing bone parts, very small joints - could be treated very well in future.
Customised production also saves time thanks to automated modelling and 3D printing: according to initial calculations by the researchers, it would be possible to save up to 60 percent of the time usually required from determining the need to inserting an implant. This means that a restoration can be carried out within a few days, which also results in lower costs in hospitals due to shorter hospitalisation times. Another advantage is that the design is modelled on the original joint, resulting in significantly improved mobility compared to previous solutions. Dr Imgrund summarises: »FingerKIt could completely change the treatment of rheumatoid arthritis, for example. Treatment with an individualised implant could become the gold standard.

Growth market for finger joint implants
According to the German Society for Rheumatology, around two percent of the adult population in Germany suffer from inflammatory rheumatic diseases, and most of them do not want to do without a good quality of life even in old age. The new development is also interesting for patients who are affected by injuries. Compared to foot or ankle implants, for example, the market for the remobilisation of finger joints is still significantly underdeveloped. The experts estimate that the total potential in 2026 is 5.8 million euros.

Technologically, the development within FingerKIt is now so far advanced that the product could be brought to market maturity together with a partner from the medical technology sector: The AI-based design creation and production work; implants ready for exhibition already exist. The next step is to take the path to authorisation. Dr Imgrund: »We are currently looking for corporate partners who can use their expertise to help us bring our AI-created medical products to market.

Source: Press release Fraunhofer-Gesellschaft. In: idw from 01.12.2022