Joint Reconstruction, Part 2 – Material Standards

Joint reconstruction implants allow millions of individuals to regain mobility and reduce pain. Just as surgical skill is required to implant these artificial joints, so is skillful construction and finish of the joint components themselves.

A leader in surface finishing for medical technology, Rosler Metal Finishing has extensive experience in shot blasting and mass finishing a wide range of medical devices from instruments to implants used specifically for joint replacement.

Our Joint Reconstruction Series continues with an overview of the most common materials used for these endoprosthetic implants.

Material Standards

The most common materials used for joint reconstruction implants are currently titanium and titanium alloys and cobalt-chromium alloys. Both materials are very tough, corrosion-resistant, highly biocompatible, and have proven themselves to be absolutely reliable.

While stainless steel is often used for trauma implants, it is not very common for joint reconstruction implants because of its limited long-term ability to withstand corrosion in the human body.

Plastic, primarily polyethylene (for example, UHMWPE), is also an important material. The interface between two joint sections can consist of metal on plastic, metal on metal, ceramic on plastic, or ceramic on ceramic.

For example, the acetabular cup of a hip implant can be lined with polyethylene, whereas the femoral head on the hip stem interacting with the acetabular cup may be made of metal. The section of the knee tibia plate interacting with the femoral head is protected with a polyethylene liner.

The acetabular cup for hip implants (left) is lined with polyethylene between the femoral head and acetabular cup. The tibia plate used for knee replacements (right) features a polyethylene liner on the tibia plate.

Ceramic

This material is described as an up-and-comer because it is quickly becoming an excellent alternative to titanium and cobalt chrome. Ceramic offers excellent wear characteristics and the best biocompatibility among the known materials.

Examples of ceramic use in joint reconstruction implants include ceramic femoral heads and ceramic knee femorals on metal tibia plates with plastic liners, and acetabular cups lined with ceramic and ceramic femoral heads for hip replacements.

Used in knee replacements, the ceramic knee femoral (left) is separated from the metal tibia plate with a plastic liner. The ceramic hip joint (right) is shown with an acetabular cup lined with ceramic and a ceramic femoral head.

Physical Vapor Deposition (PVD) Coatings

Joint reconstruction implants frequently receive a Physical Vapor Deposition coating, known as PVD, mainly with titanium nitride (TiN).

These coatings provide several advantages including:

  • Improved wear resistance.
  • Reduced friction.
  • High biocompatibility.
  • Decorative colors.

An example of PVD coating is this femoral head with a two-tone finish.

Plasma-coated examples of joint replacement implants include (from left) acetabular cups, hips stems, and tibia plates.

Plasma Coating

Primarily used to promote osseointegration on those surface areas of implants that must bond with the surrounding bone tissue, plasma coating ensures perfect adhesion of the coating. The respective surface area must then be textured through shot blasting to add a rough finish.

Examples of plasma coated implants include acetabular cups, hip stems, and tibia plates.

An example of a PVD-coated hip stem with femoral head.

The Rosler Way

Whatever industry we work in, we apply The Rosler Way. That means we learn about your work piece and process in order to develop a solution and deliver precision surface finishing and process improvements. Our work in the medical industry and with joint reconstruction implants is no exception.

Whatever your joint reconstruction implant process calls for, we are confident that we can collaborate to find a better way. Contact us today to discuss your unique challenges.

Be sure to catch up on our previous posts in the series, Part 1 – Expertise for Endoprosthetics.

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