Implants for knee reconstruction

Manufacturers of knee reconstruction products are now in a global market for sales and customers. Apart from the actual implants, tools and instruments, which facilitate handling during the operation, enhance patient safety and may even reduce the follow-up expenses for reprocessing, are also of increasing importance. These instruments include test / trial implants, which sometimes serve to differentiate products from the competitors.

The knee joint implant is a polyethylene inlay. Trial implants made of thermoplastic materials like TECASON P MT (the so called UHMWPE inlay) have been used successfully in test implants for years. However, all other test implants - including femur components, tibia components and possibly the shafts - have usually been made of metal.

  • However, with metals, there is an increased risk of bioincompatibility. For metals, biocompatibility is only tested and confirmed for the surface alloy. In the event of damage, biocompatibility may thus be forfeited. 
  • The metal components used up to now have a high dead weight, which may increase the operating expenses during sterilisation: depending on the instrument set, many trays may have to be reprocessed, as the acceptable total weight is soon exceeded with the heavy metal parts.
  • Transmission of X-rays would be particularly important for testing the goodness of fit. However, this is impossible with metals.

The future of test implants 

In collaboration with our customers, we have succeeded in almost totally replacing metals in test implants - including femur and tibia components and shafts - with thermoplastic materials such as TECASON P MT or TECAPEEK MT. 
The most important requirement is consistent biocompatibility. All our MT plastic semi-finished products are therefore tested in accordance with ISO 10993. Biocompatibility is retained, even if the surface of the plastic test implants is damaged. 

The range of Ensinger MT plastics is extended by XRO types (X-ray opaque plastics). By using TECAPEEK MT XRO and TECASON P MT XRO, it is possible to specifically control which parts are visible in the X-ray. This allows the control X-ray to be used to estimate the precision of fit.
There is an extensive colour palette within the MT range, which greatly increases flexibility in designing the test implants. The sizes of the test implants are colour-coded with different colours. This simplifies handling during the operation, as well as measurement of the implant fit on the patient.
Not only can MT plastics be dyed, but also labelled with a laser. Both facilitate branding of the test implants. 

The special properties of our high-performance plastics permit creative solutions, even during the design stage. For example, with TECASON P MT, strength and stiffness are ideally balanced. Also, demanding constructional elements such as snap hinge connections can be realised, which is impossible with metal. 
 

Benefits 

Strengthening trade name and product branding

Particularly in medical devices, where the form has to follow the function, it is difficult to distinguish products by design. By using plastic of different colours, with laser labelling and with the design flexibilities permitted by the mechanical properties of our plastics, we have gained additional freedom in design. This makes it possible for manufacturers to distinguish their product from their competitors.

Cheap processing and reduced reworking

Plastics can be machined more easily and more rapidly than metals. Sharp-edged or unribbed sections and difficult surfaces can be implemented more easily, reducing necessary reworking such as deburring. 

Long clinical use

MT plastics are very resistant to a variety of sterilisation procedures, such as superheated steam sterilisation, and are also very resistant to chemicals. This gives test implants that are only made of plastics a very long lifetime in clinical use. 

More test implants per tray due to low weight

The low specific weight of the MT plastics is of considerable economic advantage. They are up to 80% lighter than steel and 50% lighter than titanium or aluminium. The greater the number of test implants that can be transported per tray, the fewer the trays in circulation. This reduces the manufacturing costs for the knee endoprosthesis manufacturers as well as the subsequent throughput times in hospitals and clinics and is therefore a strong sales argument.

Safety in product registration

The product registration procedure in the highly sensitive area of medical devices is often very complex and demanding. During product development, the biocompatibility test of the semi-finished product supports the user in risk assessment and improves safety. We also aim to build up and sustain long-term partnerships with our customers and suppliers.  This assures constancy in the formulation and use. If, however, changes are inevitable, we will of course act without delay in accordance with a reliable Change Notification Commitment.

Materials for Knee trial implants