Dr.-Ing. Tassilo Moritz
Chronic knee pain and reduced mobility is a big medical issue affecting an increasingly large number
of the adult population. This can be the result of deterioration in the cartilage, which can worsen
over time if not treated properly. In some cases, massive bone resection typical for total knee
replacement can be avoided. Small osteochondral defects can be treated with partial knee
replacements (also called knee partial resurfacing). That is a less invasive solution with advantages
such as less bone resection, arthroscopic surgery and less blood loss, therefore shorter recovering
Due to the complexity of the human knee, the orthopaedic community generally agrees that
implants customized and adapted to the knee anatomy of each patient can improve the success of
the surgery. Every patient has a unique anatomy, size, and position of defects. Furthermore, the
fixation of the implant itself in the bone is a huge challenge.
Advantages with 3D printed knee implants
1. The conventional ceramic manufacturing (i.e. green machining by milling and turning)
has limitations which make the production of subject specific samples with textured or
trabecular ceramic difficult or too expensive. The goal is to quickly manufacture less
expensive customised implants;
2. Create porous rough surfaces that stimulate the bone ingrowth and the bone integration
between the bone and the implant;
3. Create a stable trabecular interconnected structure without the risk of debris release in
the body that can lead to implant loosening.
In order to simulate real patient cases, CeramTec created CAD models of knee implants based on
knee surfaces reconstructed from diagnostic CT patient datasets. The patient knee surfaces which
were provided by Rizzoli Orthopaedic Institute (Bologna, Italy) were completely anonymised
following the Data Protection Directive 95/46/EC ? EUR-Lex – Europa and national specific ethical
rules (§§1-1, 27-38a BDSG).
The CAD model in the picture below is an example of a first prototype subject?specific unicondylar
implant designed to best fit the patient’s knee condyle geometry.
These products are under development and are not approved by any authority.
Printed knee implant
This case study was designed to comprehensively test and evaluate new materials, feedstocks, devices and processes.
The final results can be seen in three videos at the Process Development page.