Copyright 2013 American Academy of Orthopaedic Surgeons
Questions and Answers About Metal-on-Metal Hip Implants

If your hip has been damaged by arthritis, a fracture, or other condition, common activities such as walking or getting in and out of a chair may be painful and difficult. You may be considering hip replacement surgery. By replacing your diseased hip joint with an artificial joint, hip replacement surgery can relieve your pain, increase motion, and help you get back to enjoying many normal, everyday activities.

How Your Hip Works

The hip is one of the body's largest weight-bearing joints. It is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone). Bands of tissue called ligaments (hip capsule) connect the ball to the socket and provide stability to the joint.

Normal hip anatomy.
Hip Replacement Devices

After you and your orthopaedic surgeon have determined you are a candidate for hip replacement surgery, your surgeon will select a hip replacement device for you based on your body structure, medical history, and lifestyle.

Many different types of designs and materials are currently used in artificial hip joints. All of them consist of two basic components: the ball component (made of a highly polished strong metal or ceramic material) and the socket component (a durable cup of plastic/polyethylene, ceramic, or metal). Sometimes, the socket is made of a different material than the ball, or is lined with a different material, and sometimes the ball and socket are made of the same material. Your orthopaedic surgeon will recommend the best combination for you.

Implant Complications

All hip implant devices — no matter what type — can have complications. The most common complications include implant dislocation and device wear.

Bone loss, or osteolysis, is also a known complication. When the ball component moves against the cup, the surface begins to wear away and small debris particles are given off. The debris remains around the joint and over time can cause the bone around the implant to thin and weaken. As a result, the implant components can loosen and additional surgery may be necessary.

Researchers are continuing to study different device surfaces in order to address the problems of wear debris and osteolysis.

Metal-on-Metal (MoM) Devices

In metal-on-metal devices both the ball and socket components are made of metal. These metal implants have been used in total hip replacement surgeries and hip resurfacing procedures.

Because of metal's durability, metal-on-metal devices were expected to last longer than other hip implants. In addition, the ball in a metal-on-metal device is larger, making the hip joint more stable and less likely to dislocate.

MoM implants have also been used because they avoid the complication of debris wear from implants made of plastic/polyethylene. However, recent information about the wear of certain metal-on-metal devices has raised concerns about their use. Like polyethylene, metal surfaces give off small particles of debris. In addition, metal surfaces can corrode, giving off metal ions. Metal debris (ions and particles) can enter the space around the implant, as well as enter the bloodstream. This can cause a reaction in some patients, such as pain or swelling around the hip, osteolysis, and very rarely symptoms in other parts of the body.

Although the vast majority of patients have not had any problems with MoM implants, orthopaedic surgeons and the U.S. Food and Drug Administration (FDA) are concerned because cases have been reported in the peer-reviewed literature and through a British database in which patients have local hip symptoms (pain and swelling). In addition, there have been a very small number of cases that have had other medical concerns seemingly unrelated to the hip.

Updates on Metal-on-Metal Devices from the FDA

On January 17, 2013, the U.S. Food and Drug Administration (FDA) issued an updated public health communication about hip replacement components that have both a metal ball and a metal socket (metal-on-metal hip devices).To read their notification: Federal Drug Administration CommunicationFederal Drug Administration Communication (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/default.htm)

On May 6, 2011, the Food and Drug Administration (FDA) issued a postmarket surveillance study of total metal-on-metal hip replacement devices. Metal-on-metal (MoM) hip devices consist of a ball, stem, and shell, all made of metal parts. A postmarket surveillance study monitors adverse events after a device has been approved or cleared by the FDA. Manufacturers of metal-on-metal hip implants have orders from the FDA to further study the safety of metal-on-metal devices FDA ActivitiesFDA Activities (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241769.htm). As a result, if you have a metal-on-metal hip replacement device, your surgeon may be contacting you to find out how your device is functioning.

In February 2011, the FDA issued their initial public safety communication about metal-on-metal hip devices.

If after a joint replacement surgery you experience pain or have other, new medical concerns or issues, please talk to your doctor or orthopaedic surgeon.

The Importance of Physician-Patient Communication

The American Academy of Orthopaedic Surgeons (AAOS) believes that physician and patient joint decision making leads to the best surgical outcomes. Share your concerns, voice your questions, and offer a complete medical history so that you and your surgeon can together develop the best plan for you.

There are many issues to discuss with your orthopaedic surgeon when you are considering total hip replacement surgery. It is helpful to make a list of the questions you would like to ask. In addition to the questions featured in this article, the AAOS provides the following suggestions: Total Joint Replacement: Questions Patients Should Ask Their SurgeonTotal Joint Replacement: Questions Patients Should Ask Their Surgeon (topic.cfm?topic=A00375)

Your surgeon will also talk with you about hip implant devices. To help you with this discussion, here are examples of questions you may want to ask your surgeon:

  • What are your experiences with specific hip implant devices and how often do you use one over the other?
  • What are the risks and benefits of different devices (metal-on-metal, metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic devices)?
  • If applicable, what is the surgeon's personal experience and outcomes with metal-on-metal hip devices?
  • If your surgeon recommends a metal-on-metal device, ask why a metal-on-metal hip implant is the best for your situation.
Frequently Asked Questions About Metal-on-Metal Hip Implants

What kind of recovery should I expect after hip replacement surgery?

After undergoing hip replacement, you may expect your lifestyle to be a lot like the way it was before, but without the pain. In many ways, you are right, but it will take time. You need to be a partner in the healing process to ensure a successful outcome. Read more: Other ResourcesOther Resources (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241771.htm )

What personal health information should I share with my orthopaedic surgeon if I am considering a metal-on-metal hip implant?

It is critical that your orthopaedic surgeon know your complete medical history including any problems you may have with your kidneys and any known sensitivities or allergies to metal — for example, if you have allergic reactions from wearing certain jewelry.

Is there a way to determine ahead of time if I might have a reaction to the metal in the metal-on-metal hip implant system?

Currently there is no widely accepted test to predict if you will develop a reaction to the metal from a hip system, and there is insufficient evidence to support using a skin patch test to determine your sensitivity to a metal-on-metal hip implant. If, however, you have a known sensitivity to metal, it is important to share that information with your surgeon.

Are there any ways to prevent the metal from reaching the joint and bloodstream if I get a metal-on-metal hip implant?

No. All artificial hips require one component to slide against another component and it is inevitable that material at the surfaces will wear as they interact. In metal-on-metal hip implants, some tiny metal particles and metal ions are released into the joint space and metal ions can potentially enter the bloodstream. Certain characteristics may place patients at risk for increased wear and metal ion production, and these patients will need closer follow-up after implantation. However, how a patient reacts to the metal is variable.

Which patients should not have a metal-on-metal hip implant system implanted?

Each type of hip implant system has its own set of benefits and risks. Metal-on-metal hip implant systems are not for everyone. You should discuss your situation with your orthopaedic surgeon to determine whether you are a candidate or not. In general, metal-on-metal hip systems are not meant to be implanted in patients:

  • Who have kidney problems
  • Who have a known allergy or sensitivity to metals
  • Who have a suppressed immune system
  • Who are currently receiving high doses of corticosteroids such as prednisone
  • Who are women of childbearing age

In addition, people with smaller body frames may be at increased risk for adverse events and device failure.

Why are women of child-bearing age not good candidates for metal-on-metal hip implants?

As discussed above, recent information shows that metal ions can leave the artificial joint and enter the bloodstream. It is not known how long they remain in blood or other organs of the body.

Some metallic ions may cross the barrier from mother to fetus through the placenta. It is not known if the amount of ions is great enough to have any effect on the growing fetus or if the presence of metal ions in the mother's bloodstream will have any effect on future pregnancies.

For this reason, it is recommended that younger women who need hip replacement surgery consider implant options other than metal-on-metal.

With the risk of adverse reactions to metal-on-metal hip implant systems, why are these devices still being offered to patients?

It is known that every different type of hip implant system has its own set of risks as well as its own set of benefits. FDA's assessment of medical devices such as metal-on-metal (MoM) hip implants is based on a risk-benefit ratio with the data available. MoM hip implants overall have been shown to provide significant benefits (e.g., high survivorship) in certain patient populations. Although the exact prevalence of adverse reactions to metal debris is not known, current experience leads us to consider the adverse outcomes to be relatively low or equal (with some designs) to other types of hip implants. Thus, for many patients, currently available information supports a favorable risk-benefit ratio.

The orthopaedic surgeon should assess the patient's individual needs and should avoid using metal-on-metal hip implants in patients where the risks outweigh the benefits.

Information for Patients Who Have Metal-on-Metal Hip Implants

How do I know if I have a metal-on-metal hip system?

Patients are usually told about the type of implant they are receiving prior to the surgery. If you are uncertain about which type you have, you should contact the orthopaedic surgeon who performed your procedure.

How often should I follow-up with my orthopaedic surgeon?

Based on your individual circumstances, your orthopaedic surgeon will determine how frequently you need to follow-up. There are some cases where your orthopaedic surgeon may recommend more frequent follow-up based on the type of hip implant, the outcome of the surgery and your recovery, and the results of blood tests or imaging procedures.

If you develop new or significantly worsening symptoms or problems with your hip, including pain, swelling, numbness and/or a change in ability to walk, contact your orthopaedic surgeon right away.

What should I discuss with my orthopaedic surgeon at each follow-up appointment?

It is critical that you talk to your surgeon about any new or worsening symptoms related to your hip, groin, or legs since your last visit. This may include pain, swelling, numbness, and change in ability to walk. It is also important that you discuss:

  • Changes in your general health
  • Whether you are being seen or treated by another physician for a new condition since receiving your metal-on-metal hip implant

What symptoms might a metal-on-metal hip implant cause?

Symptoms may include hip/groin pain, local swelling, numbness or changes in your ability to walk. There are many reasons a patient with a metal-on-metal hip implant may experience such symptoms and it is important that you contact your surgeon to help determine why you are having them.

Are there other medical effects that can occur with my metal-on-metal hip implant system?

Metal-on-metal hip implants, like other types of hip implants, are known to have adverse events, including infection and joint dislocation. There are some case reports of the metal particles causing a reaction around the joint, leading to deterioration of the tissue around the joint, loosening of the implant, and failure of the device, as well as some of the symptoms described above. In addition, some metal ions from the implant may enter into the bloodstream. There have been a few recent case reports of patients with metal-on-metal hip implants developing a reaction to these ions and experiencing medical problems that might have been related to their implants, including effects on the nervous system, heart, and thyroid gland.

What are my chances of developing a reaction to my metal-on-metal hip implant and having these types of medical problems?

Although current data suggests that these events are rare, it is currently unknown how often they occur in patients with metal-on-metal hip implants.

Part of the difficulty in answering this question is that individuals vary in how they react to metal ions in their bodies. For example, a reaction may develop in Patient A in response to a very small amount of metal, whereas Patient B may be able to tolerate a much larger amount before a reaction develops.

What should I do if I am experiencing adverse events associated with my metal-on-metal hip implant?

  1. If you are experiencing hip/groin pain, difficulty walking or a worsening of your previous symptoms, you should make an appointment to see your orthopaedic surgeon for further evaluation of your implant. Your orthopaedic surgeon may wish to perform a physical exam and an evaluation based on your symptoms.
  2. If you experience any new symptoms or medical conditions in your body other than at your hip, you should report these to your primary physician and remind them that you have a metal-on-metal hip implant system during their evaluation.

What should I do if I am not experiencing adverse events associated with my metal-on-metal hip implant?

If you are not having any symptoms and your orthopaedic surgeon believes the metal-on-metal hip implant is functioning appropriately, there are no data to support the need for additional tests. You should continue to follow-up with your orthopaedic surgeon for periodic examinations.

What should I discuss with my other healthcare providers including my general internist or family practice doctor?

There are rare case reports of patients with metal-on-metal hip implants who experienced medical problems in areas of the body away from their hip implant. This may have resulted from the metal ions released by the metal-on-metal hip implant.

If you see a healthcare provider for the evaluation of any new or worsening symptoms outside the hip/groin area, including symptoms related to your heart, nervous system, or thyroid gland, it is important that you tell that clinician of your metal-on-metal hip implant. This information may affect the types of tests that are ordered to further evaluate the cause of your symptoms.

When would a hip revision surgery be needed?

There are multiple reasons why a surgeon may recommend a device revision (a surgical procedure where your implant is removed and another put in its place). Many of these reasons, including infection, dislocation, and device fracture, apply to any type of hip implant. Your surgeon might also consider revision if you develop evidence of local or systemic reactions to the metal from your hip implant. In that case, the surgeon will take several factors into account in considering if and when a revision surgery is advisable.

What are the risks of revision surgery?

Any surgical procedure, including revision surgery, has risks associated with it, including reaction to the anesthesia, infection, bleeding, and blood clots. The revision surgery may be more difficult if you had a local reaction to the implant that may have affected your soft tissue and/or bone quality.

What does it mean when I see that a hip implant system has been "recalled?"

A hip system may be recalled by the manufacturer for a number of reasons. If your device is recalled, this does not necessarily mean that the device needs to be removed and replaced. In some cases, the recall just calls for different or more frequent monitoring. It is important to discuss the reason for the recall with your surgeon to determine the most appropriate course of action. If you are unsure if your hip implant was recalled, consult with your orthopaedic surgeon. Additional information on the recall can be obtained from the manufacturer or from: ()).

Where can I get additional information regarding metal-on-metal hip systems?

Please see Other ResourcesOther Resources (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241771.htm )

Source: This article includes information from the U.S. Food and Drug Administration communications regarding metal-on-metal hip implant systems.

Last reviewed: January 2013
AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS "Find an Orthopaedist" program on this website.
Copyright 2013 American Academy of Orthopaedic Surgeons
Related Articles
AAOS Media Advisory, January 2013 (http://newsroom.aaos.org/media-resources/news/hip-implants.htm)
Activities After Hip Replacement (http://orthoinfo.aaos.org/topic.cfm?topic=A00356)
FDA Activities (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241769.htm)
Federal Drug Administration Communication (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/default.htm)
Other Resources (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241771.htm )
Total Hip Replacement (http://orthoinfo.aaos.org/topic.cfm?topic=A00377)
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