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What the FDA has to say About Metal on Metal Hips
FDA Website – click here
Metal-on-Metal Hip Implants
Hip joint deterioration can lead to symptoms such as pain, stiffness or difficulty walking. When symptoms do not respond to conservative treatment, patients may be advised to undergo total hip replacement or hip resurfacing. Patients may receive a “metal-on-metal” hip implant in which the “ball and socket” of the device are both made from metal.
In this website, the FDA describes hip implants, how metal-on-metal implants differ from other hip implants and gives information and recommendations for patients and physicians about the benefits and risks of these products.
Concerns about Metal-on-Metal Hip Implant Systems
All artificial hip replacement systems have risks related to implant or material wear. Metal-on-metal hip (MoM) replacement systems have unique risks in addition to the general risks of all hip implant systems.
Because the metal ball and the metal cup slide against each other during walking or running, some tiny metal particles may wear off of the device and enter into the space around the implant. Some of the metal ions from the metal implant or from the metal particles may even get into the bloodstream.
Orthopaedic surgeons take several precautions before and during the implantation surgery to try to optimize the way in which the ball and socket rub against each other so that fewer wear particles are produced. However, there is no way to fully avoid the production of metal particles.
Different people will react to these metal particles in different ways. At this time, it is not possible to know who will experience a reaction, what type of reaction they might have, when the reaction will occur, or how severe the reaction will be. However, it is known that over time, the metal particles around some implants can cause damage to bone and/or tissue surrounding the implant and joint. This is sometimes referred to as an “adverse local tissue reaction (ALTR)” or an “adverse reaction to metal debris (ARMD).” Such a reaction may cause the implant to become loose or cause pain. Ultimately this can require a revision surgery where the old device is removed and replaced with another one.
In addition to these reactions to metal near the joint and implant, there are some case reports in the literature of a small number of patients in which high levels of metal ions in the bloodstream may have caused other types of symptoms or illnesses elsewhere in the body, including effects on the heart, nervous system, and thyroid gland.
Patients who have MoM hip implants should be aware of potential symptoms which may occur after surgery and indicate that their device is not functioning properly. Common symptoms may include:
- Pain in the groin, hip or leg
- Swelling at or near the hip joint
- A limp or change in walking ability
There are many reasons why any of these symptoms may arise or worsen after surgery and it does not necessarily mean that a reaction to the metal particles from the device is taking place. A thorough evaluation by an orthopaedic surgeon is needed to determine the actual cause. Besides a physical exam of the hip, the orthopaedic surgeon may consider several tests to evaluate these symptoms including:
- Special imaging tests
- Using a needle to remove fluid from around the joint (joint aspiration)
- Blood tests, including checking levels of metal ions in the blood
Patients who receive a MoM hip implant should also pay close attention to changes in their general health or new symptoms outside their hip including symptoms related to their:
- Heart (chest pain, shortness of breath)
- Nerves (numbness, weakness, change in vision or hearing)
- Thyroid (fatigue, feeling cold, weight gain)
- Kidney (change in urination habits)
In April 2010, the United Kingdom’s (U.K.) Medicines and Healthcare products Regulatory Agency (MHRA) issued a medical device alert that included specific follow-up recommendations for patients implanted with MoM hip replacements. The recommendations included blood tests and imaging for patients with painful MoM hip implants.
There are several differences between the U.K. and U.S. regulatory systems and some of the U.K. data may not be directly applicable to the experience in the US. For example, some of the devices available in U.K. are not marketed in U.S. Therefore, the frequency of the reactions described above, in the U.S. is unknown. For this reason, FDA is in the process of gathering additional information about adverse events in people with metal-on-metal hip implants.
At the current time, there is no evidence to support the need for checking metal ion levels in the blood or special imaging if patients with MoM hip implants have none of the signs or symptoms described above and the orthopaedic surgeon feels the hip is functioning properly. The FDA is recommending that asymptomatic patients with MoM hip implants continue to follow-up with their orthopaedic surgeon as prescribed.
If patients with MoM hip implants develop any of the symptoms above, it is very important for them to make appointments with their orthopaedic surgeons promptly for further evaluation.
If patients with MoM hip implants develop any new or worsening symptoms outside of their hips, or if they are referred to doctors to evaluate new conditions, they should let the doctors know that they have MoM hips.
Information for Orthopaedic Surgeons about Metal-on-Metal Hip Implant Surgery
Effectiveness of Metal-on-Metal Hip Implant Systems
The 2010 report from the Australian Orthopaedic Association’s National Joint Registry notes that in patients with a primary diagnosis of osteoarthritis, 92 percent of metal-on-metal hip replacements survive at seven years. Randomized clinical trials comparing conventional metal-on-polyethylene total hip replacements to metal-on-metal implants have demonstrated favorable short-term results. However, long-term results comparing the two systems have not yet been reported.
Observational clinical studies account for the majority of published literature on total hip replacement (hip arthroplasty) and hip resurfacing. These clinical studies play a critical role in evaluating metal-on-metal hip performance and survival. The device survival estimates range from 95.5 percent at twelve years to 93 percent at ten years.
General Considerations BEFORE Metal-on-Metal Hip Implantation Surgery
- Because the success of metal-on-metal (MoM) hip systems is highly dependent on proper implantation technique, you should use MoM hip only if you are:
- trained in the technical aspects of each individual implant and its unique surgical instrumentation, and
- familiar with the manufacturer’s specific recommendations for implantation and surgical technique.
- Do not implant MoM hip systems in:
- Patients with known moderate to severe renal insufficiency
- Patients with known metal sensitivity (e.g. cobalt, chromium, nickel)
- Patients with suppressed immune systems
- Patients currently receiving high doses of corticosteroids
- Females of childbearing age
- Be aware that previously implanted hardware at or near the hip joint may impact the generation of wear debris or the amount of metal exposure to the patient who receives a MoM implant.
- When obtaining informed consent for MoM hip procedures, ensure that the patient understands:
- The alternative treatment therapies along with their respective risks and benefits.
- The potential risks associated with MoM systems which include but are not limited to:
- Elevated metal ion levels in the joint and blood.
- Development of local inflammatory reactions and lesions including soft tissue masses and tissue necrosis.
- Development of potential systemic events related to elevated metal ion levels.
- The potential for and risks of revision surgery.
- There is currently no evidence to support the use of pre-operative skin patch testing to predict implant sensitivity prior to surgery.
General Considerations DURING Metal-on-Metal Hip Implantation Surgery
- Follow the manufacturer’s surgical technique guide and instructions for use. Accurate surgical technique is essential since metal-on-metal (MoM) hip systems are sensitive to correct placement and implantation.
- Do not mix components from different manufacturers’ devices because each hip system has different metallurgy and design specifications. It is imperative that all implanted components and their associated instruments be from the SAME manufacturer’s marketed hip implant system
- Pay particular attention to the angles of inclination and anteversion of the acetabular cup. Malposition may predispose the device to excess wear and early failure.
General Considerations AFTER Metal-on-Metal Hip Implantation Surgery (Follow-up)
- At the time of hospital discharge, review with the patient or caregiver the signs/symptoms of potential local and systemic adverse events which may result from reaction to metal debris.
- Schedule the patient for routine office follow-up.
- Schedule patients with increased risk of device wear or adverse reaction to metal debris (ARMD) for closer follow-up. These may include:
- Patients with components not aligned optimally
- Patients with bilateral implants
- Patients with increased activity levels
- Patients who are severely overweight
- Female patients or patients with small femoral heads
Follow-Up for Metal-on-Metal Hip Patients Developing Local Signs/Symptoms
Clinical and Imaging Evaluation
If you have a patient with the presence of local symptoms such as pain or decrease in joint function that appear more than three months after metal-on-metal (MoM) hip implant surgery, you should conduct a thorough evaluation.
- Guide your clinical evaluation by the symptoms and physical findings, including an assessment for well-known emergent complications including joint infection, implant loosening, peri-prosthetic fracture and dislocation.
- Recognize that localized lesions associated with reactions to metal debris may also present with pain or a variety of other signs/symptoms including:
- Local nerve palsy
- Palpable mass
- Local swelling
- Joint dislocation or subluxation
- Consider using diagnostic imaging procedures as part of the evaluation noting the following:
- The risks and benefits of using different types of diagnostic imaging procedures should be considered when determining the most appropriate imaging modality.
- FDA guidance recommends that labeling for an implant without a source of electrical energy (passive implant) address its safety and compatibility in a magnetic resonance (MR) field. Check the device-specific labeling for this information.
Metal Ion Testing
- If metal ion (e.g. cobalt and chromium) levels are assessed, interpret the values in the context of the overall specific clinical scenario including symptoms, physical findings, and other diagnostic results when considering further actions. If clinical and imaging evaluations lead to the suspicion of an adverse reaction to metal debris (e.g., soft tissue mass), consider assessing and monitoring serial metal ion levels.
- Increases in metal ion levels over time may be suggestive of significant and/or continuing device wear which may lead to failure of the device requiring revision.
- When assessing metal ion levels, it is important to determine if the patient has any other reasons to have elevated levels including:
- Other implanted metal hardware
- Occupational exposure
- Renal insufficiency
- Dietary supplements
- Despite the recommendations of other international regulatory agencies, the FDA currently believes there is insufficient evidence to correlate the presence of localized lesions, clinical outcomes, and/or the need for revision with specific metal ion levels for individual patients.
- Although there are currently no commercially available standardized tests to assess metal-ion levels, there are a few laboratories in the U.S. that are able to perform these analyses.
- Consult with your normal test laboratory to determine if they are able to conduct metal ion testing, and if so, how specimens should be collected.
- Metal ion testing using whole blood versus serum will give different results. When following serial levels in a particular patient, ensure the same metal ion testing method is used each time for the analysis.
- Note that FDA does not regulate tests that are individually developed and used only in a single laboratory.
Assessment for Systemic Effects
- Patients with evidence of excessive device wear or a localized adverse reaction to metal debris (ARMD) should also be assessed for potential systemic effects of exposure to metal ions. Although only a few case reports in the literature describe potential systemic effects of metal ions associated with metal-containing hip implant systems, a thorough physical examination should be performed with particular focus on cardiovascular, neurological, renal and thyroid signs/symptoms.
- Because metal ions are cleared through the kidneys, a patient who has renal insufficiency may be at higher risk for systemic adverse events.
- There are currently insufficient data to identify any specific numerical values for blood metal ion levels that would cause or correlate with adverse systemic effects for an individual patient.
- Evaluate patients with new systemic symptoms in collaboration with their primary medical physicians or specialists to determine the cause of their symptoms or findings.
- At this time, there is insufficient scientific data to provide a rigorous science-based recommendation for a threshold value of metal ion levels in the blood that would serve as a trigger for intervention or revision.
- The decision to revise a patient’s MoM hip implant should be made in response to the overall clinical scenario and results of diagnostic testing.
- If you recommend revision, advise patients of the surgical risks of revision as well as the expected outcomes including the potential need for a future revision procedure.
- When possible, contact the manufacturer prior to revision surgery for instructions on returning the implant for analysis.
- A retrieval analysis will be most informative in those cases where there is no obvious cause for implant failure such as malposition, or likely risk factors.
- long with the implant, provide non-identifying information about the patient, the date of procedure, observations from the revision surgery and the histopathology report from any tissue sent to the hospital pathologist.
- Report any adverse events believed to be related to the MoM system to FDA through MedWatch, the FDA Safety Information and Adverse Event Reporting Program.
Follow-Up for Asymptomatic Patients
- Follow-up of asymptomatic metal-on-metal (MoM) patients should occur periodically.
- Patients, including the following, are at risk for increased device wear and/or adverse reactions to metal debris and should be monitored closely:
- Female patients
- Patients with increased activity
- Patients with malpositioned components
- Patients with bilateral implants
- Patients with evidence of renal insufficiency
- Patient follow-up visits should include:
- Careful exam which includes a functional assessment
- Physical examination for asymptomatic local swelling or masses
- Careful review of systems for general health changes and evidence of systemic effects (particularly as pertains to the cardiovascular, neurological, and thyroid systems)
- At this time, the utility of routine screening of asymptomatic patients using diagnostic soft tissue imaging and/or blood metal ion testing has not been established. Moreover, findings of lesions on soft tissue imaging, or of elevated blood metal ions, in the absence of symptoms, though reported in a limited number of research studies for some MoM hip implant patients, are difficult to interpret because:
- The exact incidence or prevalence of asymptomatic lesions and their natural history is not known
- The correlation between elevated blood metal ions and development of future local or systemic system adverse reactions is not well established
- A limited number of case reports in the medical literature have suggested the potential for systemic effects of elevated metal ion levels resulting from device wear in metal-on-metal (MoM) hip systems. These effects have included cardiomyopathy, thyroid dysfunction, and neurological changes including sensory, auditory, and visual impairments.
- Based on the limited number of case reports in published literature, the true incidence or prevalence of adverse systemic effects from MoM hip implants is not known at this time, but is believed to be rare.
- As a patient with systemic symptoms and a MoM hip implant is more likely to visit his or her general practitioner or medical specialist rather than his or her orthopaedic surgeon, it is imperative that all clinicians be aware of the potential role of metal ions during their evaluation of any such patient.
- There are currently insufficient data to identify any specific metal ion levels that would cause adverse systemic effects. As a result, it is not possible to cite a metal ion threshold value in the blood that would serve to confirm the etiology of the symptoms.
- If the patient’s systemic findings are thought to be related to the MoM hip implant, the patient should follow-up with his or her orthopaedic surgeon to determine the appropriate course of action.
- Report any adverse systemic events which are believed to be related to MoM hip implants to the FDA through MedWatch, the FDA Safety Information and Adverse Event Reporting Program.
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?
- 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.
- 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 health care 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 health care 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: FDA: Medical Device Recalls.
Where can I get additional information regarding metal-on-metal hip systems?
Please see “Other Resources“.
Information for Patients Considering a Metal-on-Metal Hip Implant System
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.
What types of questions should I ask my orthopaedic surgeon about metal-on-metal hip implant systems?
When discussing your options for hip surgery with your surgeon, some questions you should ask include:
- What are the risks and benefits of each type of hip implant system (metal-on-metal, metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic devices)?
- Why is a metal-on-metal hip implant the best for your situation?
- What types of reactions may occur due to metal ions and how they would be evaluated and treated?
- What is the surgeon’s personal experience and outcomes with metal-on-metal hip systems?
What personal 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.
What are the risks of having a metal-on-metal hip implant system?
See the section above, called “Information for Patients who have Metal-on-Metal Hip Implants.”
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 or metal ions being released into the joint space and potentially metal ions entering 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.
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 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.
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