What are joint replacements made of?

Health and wellness

For the last two decades, the number of total joint replacements has steadily increased in the U.S. If you’re a candidate for total joint replacement, you may be wondering, what are joint replacements made of, and which one is best one for me?

Bertrand Kaper, MD, orthopedic surgeon at HonorHealth, explains the different components and materials used for two of the most common total joint replacements – hip and knee.

“Total hip and knee replacements are some of the most successful orthopedic procedures available. The bulk materials used to make hip and knee replacements are quite similar and have not changed drastically in the last 30 years,” says Dr. Kaper.

Total hip replacement materials

Standard total hip replacement implants are made up of four individual components, including the:

Stem (trunnion): The portion of the replacement that fits into your thigh bone. Stems are made from cobalt-chromium or titanium, which have excellent long-term results.
Cup (acetabulum): Fits into your pelvis and is made from titanium or tantalum metals, which serve as an excellent surface for bony attachments.
Ball (femoral head): Fits on the end of a taper-shaped stem, which wedges it into position and holds it tightly in place with friction. The ball comes in varying diameters and is made from materials such as ceramic or cobalt-chromium.
Liner (acetabular): The liner fits into the cup and serves as your new cartilage. It is susceptible to wear and considered the “weak link” of total hip replacement. Liners are made out of different materials, including ceramic, cobalt-chromium or polyethylene.

Total knee replacement materials

Total knee replacement implants are made up of four individual components, including:

Thigh (femur): Made out of cobalt-chromium and have long-term success rates.
Shin (tibia): Made from either titanium or cobalt-chromium with excellent results for each. This portion of the replacement is meant to hold the plastic liner.
Liner (polyethylene): Fills the space between the two metal pieces. As with the total hip replacement, it’s considered the “weak link” and can wear out with time.
Kneecap (patella): Not all surgeons use this implant; however, if your surgeon elects to, the undersurface is covered with a piece of a plastic.

Metal allergies

While the likelihood of having an allergy to the materials in total joint replacements is low, there has been a notable shift towards using materials that lower the risk of allergic reactions. Metal allergy testing is also available. This serves as a valuable tool to identify potential allergies.

Which implant is best for me?

Studies show hip implants can last beyond 15 years from the original surgery, and the success rate for total knee replacement is outstanding, lasting between 15 to 20 years, making them vital in restoring mobility and improving your quality of life.

Asking questions and discussing implant options with your surgeon will give you a better understanding of the different materials available, and which is the best implant for you.