Researchers of the Faculty of Mechanical Engineering, BUT (FME BUT), are participating in the development of an individual segmental joint replacement that is to help patients with avascular necrosis of the hip joint. Thanks to 3D printing, advanced design of porous structures, optimisation of the friction surface and cooperation with the University of Chemistry and Technology in Prague and a clinical department at the Faculty Hospital in Motol, the new replacement may significantly delay the implantation of a total endoprosthesis in the future, especially in younger patients.

Avascular necrosis is a disease in which part of the bone dies due to impaired blood supply. In the case of the hip joint, it often affects the head of the femur and subsequently leads to damage to the articular cartilage, pain and significant limitation of movement. If the disease progresses further, the last option is to implant a total joint replacement. However, this solution has a limited lifespan and, in younger patients, means a high risk of repeated surgeries throughout life.

“The purpose of the project is to replace only the damaged segment of bone and cartilage, not the entire joint. In young patients, we can thus gain time and postpone total endoprosthesis by many years,” explains Martin Vrbka, Head of the Biotribology Research Group at the Faculty of Mechanical Engineering of BUT.

What is avascular necrosis of the hip? · a disease caused by a disorder of the blood supply to the bone · most often affects the femoral head · leads to pain, limited movement and damage to the articular cartilage · in younger patients, treatment with a total endoprosthesis is problematic due to its limited lifespan; reoperation is possible, but risky (depending on the condition of the bone beds for fixation), expensive and psychologically demanding for the patient

The project connects two research areas from the Institute of Machine nad Industrial Design, FME BUT: the aforementioned biotribology, i.e. the science of lubrication, friction, and wear in living organisms, and additive technology, which is a manufacturing method that creates three-dimensional objects by gradually adding material in thin layers based on a digital 3D model. The goal is to develop a local implant designed individually according to the patient's CT data and manufactured using 3D printing from titanium alloy.

We design the porous fixation part of the implant so that its mechanical properties are as close as possible to the spongy structure of the femoral head. The structure must transmit high loads during walking and movement and at the same time allow the bone to grow into it well,” describes Daniel Koutný, an expert in additive technologies from the Faculty of Mechanical Engineering of BUT.

The behaviour of the implant in contact with the original articular cartilage is also crucial. “The hip joint is one of the most stressed joints in the body – during normal movement, it is subjected to forces equivalent to several times the body weight. Our goal is to design the friction surface of the implant so that it has the lowest possible friction and minimises wear of the opposing cartilage in the hip socket,” adds Vrbka, adding that some students are also involved in the development in the form of their final theses.

The research would not be possible without the joint forces of experts from various fields. Therefore, the development is also being carried out by the University of Chemistry and Technology in Prague (VŠCHT), which focuses on surface treatments of the fixation part of the implant, together with the FME BUT. The porous structure of the implant is to be supplemented with bioactive layers and drug carriers supporting osteointegration and healing after surgery. “The porous part of the implant is an excellent place for anchoring drugs and antibacterial substances. At VŠCHT, we are developing layers and substances that will be applied to the porous part of the implant and that will gradually release medicinal substances – antibiotics, antibacterial substances that prevent infection, etc.,” explains Dalibor Vojtěch, Head of the Institute of Metallic Materials and Corrosion Engineering at VŠCHT.

The clinical partner of the project is the Faculty Hospital in Motol, which ensures the selection of suitable patients and provides data for the design of implants. "Current treatment options for avascular necrosis are limited and often involve highly invasive procedures that may not provide long-term benefits," says leading Czech orthopaedist Vojtěch Havlas, adding that if avascular necrosis causes extensive damage to bone tissue and adjacent cartilage, the last option is often the implantation of a total joint replacement, which, however, is not ideal in younger patients due to its limited lifespan.

"The project therefore aims to develop a 3D printed segmental implant for the femoral head area, which will be individually tailored to the patient according to the extent and anatomical location of the defect. This will offer our patients a less invasive type of surgical procedure consisting of a segmental replacement of part of the femoral head. The possibility of expanding this technology to other joints such as the knee, shoulder and talus promises wider use in orthopaedic surgery, which could mean a revolution in the treatment of osteochondral defects in the human body," believes Havlas.

The research is funded by the Agency for Health Research of the Czech Republic and will run until 2028. Its main output is to be a functional sample of an individualized implant and a methodology for its design, production and testing, which is to be followed by further research and clinical verification. The researchers point out that this is not yet a solution intended for all patients immediately. This is a research project, and its goal is to develop and test a new type of implant that could expand the treatment options for selected patients with specific problems in the future.