Hip implants are medical devices intended to restore mobility and relieve pain usually associated with arthritis and other hip diseases or injuries. Every hip implant has benefits and risks. Every hip implant system has unique device design features such as size, shape, and material, and dimensions. In addition, the same hip implant system may have different outcomes in different patients. There are several factors that may influence the outcome and longevity of a hip implant including the device design features, surgeon experience and implantation technique, and individual patient characteristics such as age, sex, weight, activity level and overall health.

Although hip replacement is typically successful, it is important to know that hip implants may need to be replaced eventually.

Materials Used in Hip Implants

In the United States, there are currently four types of total hip replacement devices available with different bearing surfaces. These are:

• Metal-on-Polyethylene: The ball is made of metal and the socket is made of plastic (polyethylene) or has a plastic lining.
• Ceramic-on-Polyethylene: The ball is made of ceramic and the socket is made of plastic (polyethylene) or has a plastic lining.
• Ceramic-on-Ceramic: The ball is made of ceramic and the socket has a ceramic lining.
• Ceramic-on-Metal: The ball is made of ceramic and the socket has a metal lining.

An orthopaedic surgeon should determine which hip implant will offer the most benefit and least risk for each patient.

As of May 16, 2016, the effective date of the final order requiring premarket approval applications for these devices, there are no FDA-approved metal-on-metal total hip replacement devices marketed for use in the US. However, there are some patients who received a metal-on-metal total hip replacement prior to May 16, 2016.

Surgical Risks

Hip surgery, like any medical procedure, has risks. The risks of surgery include:

• A reaction to the anesthesia
• Heart attack
• Wound infection
• Excessive bleeding
• Blood clots

There may be adverse events after surgery, regardless of the type of hip system implanted, including:

• Hip dislocation, when the ball of the thighbone (femur) slips out of its socket in the hip bone (pelvis)
• Bone fracture
• Joint infection
• Local nerve damage with numbness or weakness
• Device loosening or breakage
• Difference in leg lengths
• Bone loss (osteolysis)
• Various types of local or systemic reactions to particles or ions generated from the use of the implant

Patients who have hip implants should be aware of potential symptoms that may occur three or more months after surgery that may indicate that their device is not functioning properly. Symptoms may include:

• Pain in the groin, hip or leg
• Swelling at or near the hip joint
• A limp or change in walking ability
• Noise (popping, grinding, clicking or squeaking) from the hip joint

Depending on the severity of the adverse event(s), additional surgery may be necessary.

This local response is sometimes referred to as an "adverse local tissue reaction (ALTR)"; the systemic and local responses are referred to as "adverse reaction to metal debris (ARMD)."

Metal-on-Metal (MoM) hip implants consist of a ball, stem and shell, all made of metal materials. MoM hip implants were designed to offer the following benefits:

Less total material being removed from the ball and socket when rubbing against each other when compared to other hip implant systems

• Decreased chance of dislocation when the ball of the thighbone (femur) slips out of its socket in the hip bone (pelvis)
• Decreased chance of device fracture

There are two types of MoM hip systems:

• Total hip replacement implant
• Total resurfacing hip implant

Metal-on-Metal Total Hip Replacement Implant

Metal-on-Metal total hip replacement systems consist of a metal ball (femoral head), a metal femoral stem in the thighbone, and a metal cup in the hip bone (acetabular component). The ball attaches to the taper of the stem.

On February 18, 2016, the FDA issued a final order requiring manufacturers to submit a premarket approval (PMA) application for two types of metal-on-metal MoM total hip replacement devices: the hip joint metal/metal semi-constrained with a cemented acetabular component and the hip joint metal/metal semi-constrained with an uncemented acetabular component.

As summarized in these final orders and given the known risks, the FDA believed there was insufficient evidence to conclude that general controls in combination with special controls would provide reasonable assurance of the safety and effectiveness of these devices. The FDA determined that these devices should remain Class III (higher risk) devices and PMA applications were to be filed with the Agency by May 18, 2016, if a manufacturer wanted to continue marketing their metal-on-metal total hip replacement devices or market new metal-on-metal total hip replacement devices.

To date, there are no approved PMA applications for metal-on-metal total hip replacements, and these devices are not currently legally marketed. However, some patients who had hip replacement prior to May 18, 2016 may have received a metal-on metal hip. Information for patients and health care providers about metal-on-metal hip implants is provided in this websection.

Metal-on-Metal Total Resurfacing Hip Implant Systems

Metal-on-Metal total hip resurfacing systems consist of a trimmed femoral head capped with a metal covering. Any damaged bone and cartilage within the socket are removed and replaced with a metal acetabular component.

To date, there are two FDA-approved metal-on-metal total hip resurfacing systems through the premarket approval (PMA) program. In each approved premarket application, the manufacturer demonstrated the safety and effectiveness of their metal-on-metal total hip resurfacing system through non-clinical and clinical performance data.

Each type of implant has its own benefits and risks. Overall, metal-on-metal (MoM) hip implants have been shown to provide high implant survivorship (no need to remove implant and put another in its place) in certain patient populations. In addition, the larger head size of MoM total hip implants is intended to reduce the risk of dislocation, which is a common adverse event associated with total hip replacements.

Metal-on-Metal Total Hip Replacement Systems

In 2011, the FDA launched the International Consortium of Orthopedic Registries (ICOR), an international collaborative effort that aims to address differences in orthopaedic registries around the world and allow for collaboration to harmonize and utilize the data available from these registries. In June 2012, the FDA's Orthopaedic and Rehabilitation Devices Advisory Panel discussed data from Orthopaedic device registries and other sources. Data from the Australian and United Kingdom Orthopaedic device registries, both of which contain the largest number of patients and the longest length of follow-up time, indicate that approximately 95 percent of patients with any kind of total hip replacement have not undergone revision surgery (a surgical procedure where your implant is removed and another is put in its place) for seven years after the initial implant.

These Orthopaedic device registries note differences in revision rates by primary diagnosis, sex and age. These registries also noted that the use of cement and the type of bearing surfaces had an impact on revision rates. More than 85 percent of patients with MoM total hip replacements from the U.K registry and more than 92 percent of patients with MoM total hip replacements from the Australian registry did not have a revision for seven years after the initial implant.

Registry data shows that MoM hip patients with larger head sizes (36 mm or larger) had more revisions than those with smaller head sizes.

When comparing outcomes of different bearing surfaces, limitations in any registry data make it difficult to draw definitive conclusions. To obtain additional data to address safety concerns related to MoM total hip replacement systems, in 2011, the FDA required manufacturers of MoM total hip replacement systems marketed in the U.S. at the time to conduct postmarket surveillance ("522") studies. Interim results of the 522 studies are provided in the FDA Activities.

Metal-on-Metal Resurfacing Hip Systems

Hip resurfacing is intended to be a bone preserving procedure on the femoral side, since failure of a resurfacing implant on the femoral side typically allows for revision to a conventional primary femoral component. Hip resurfacing implants are only available with metal-on-metal (MoM) bearings in the U.S.

Potential advantages of total hip resurfacing over total hip replacement is an area of controversy among orthopaedic surgeons. These include ease of revision, a decreased risk of hip dislocation, more normal gait, and an increased incidence of return to high-demand activities.

These potential advantages are outweighed by the increased risks for some categories of patients. These risks include increased risk of hip fracture and adverse reaction to metal debris. Pandit et al. noted pseudotumors in a case series of 17 female patients (20 hips) who underwent surface replacement arthroplasty. Similarly, smaller component sizes have been associated with increased revision rates. However, in a recent study of the Birmingham Hip Resurfacing (BHR), an estimated rate of survival of 97.2% and 93.8% at 5 and 10 years was demonstrated. When this group limited the use of BHR to their current inclusion criteria of active males <60 years of age with a primary diagnosis of osteoarthritis and anatomy conducive to a femoral head component of 48 mm diameter, the survival rate was 98.1% and 96.8% at 5 and 10 years, respectively.

The manufacturers of MoM resurfacing hip systems are still conducting long-term post-approval studies assessing device survivorship and metal ion levels; the data will be made available after completion of all of the studies.

All artificial hip implants carry risks including wear of the component material. Metal-on-metal (MoM) hip implants have unique risks in addition to the general risks of all hip implants.

In MoM hip implants, the metal ball and the metal cup slide against each other during walking or running which can cause the release of metal particles. Metal can also be released from other parts of the implant where two implant components connect. The sliding metal surfaces will cause some tiny metal particles to wear off of the device into the space around the implant. Wear and corrosion at the connection between the metal ball and taper of the stem may also occur. Some of the metal ions (e.g. cobalt and chromium) from the metal implant or from the metal particles will enter the bloodstream.

Orthopaedic surgeons take several precautions before and during hip replacement 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 ions and some metal particles.

Different people will react to these metal ions and particles in different ways. At this time, it is not possible to predict who will experience a reaction, what type of reaction they might have, when the reaction will occur, or how severe the reaction will be.

Over time, the metal particles around some implants can cause damage to bone and/or tissue surrounding the implant and joint. This local response is sometimes referred to as an "adverse local tissue reaction (ALTR)"; the systemic and local responses are referred to as "adverse reaction to metal debris (ARMD)." Soft tissue damage may lead to pain, implant loosening, device failure, and the need for revision surgery (the old device is removed and replaced with another one). Patients with a progressing ALTR may be considered for earlier revision to prevent extensive damage to bone, muscle and nerves.

Metal on Metal Hip Implants Outside of the United States

Much of the available data regarding hip implants, including Metal-on-Metal (MoM) implants, involve registry data from countries outside the United States. Although the safety concerns for patients who have MoM hip implants are present throughout the world, there are differences both in device usage and device design of MoM hip implants in the United States and those outside the United States. When comparing U.S. patients to those in other countries, it is important to be aware of the differences. Since much of the available data are from countries outside the U.S., the data are not necessarily indicative of U.S. outcomes.

In June 2012, the FDA asked members of the FDA's Orthopaedic and Rehabilitation Devices Advisory Panel to discuss these differences and the following points were highlighted:

• Device Availability – There may be physical differences between a device marketed in the U.S. and a device marketed outside the U.S. under the same name. Devices used in other countries may not be available in the U.S., and among devices available around the world, device popularity and usage vary. There may also be substantial differences in the practice of "mixing and matching" implant components between the U.S. and other countries.
• Healthcare System – National guidelines regarding patient eligibility for hip implants can result in differing timeframes between diagnosis of a patient's underlying hip disorder and hip replacement surgery. For example, patients outside the U.S. may wait longer to receive a hip implant. This could mean patients are treated at a later stage of disease and/or later age, which will impact the device selected for treatment and the outcomes of hip surgery.
• Practice of Medicine – Surgeon experience and training programs differ between countries. In the U.S., there is greater variety in surgeon experience and hospital volume in comparison to some other countries, where hospitals are more focused on certain types of procedures. In the U.S., approximately half of all primary hip replacements are performed by surgeons who typically do fewer than 15 to 20 of these surgeries per year.
• Population – Factors including a patient's age, sex, weight, diagnosis and activity level influence the lifespan of a device. These factors may vary more in the U.S. population than in other countries, which may influence the outcomes of hip surgery including the revision rate or implant survivorship (need to remove implant and put another in its place).
• Patient Expectations – Patients may have different expectations for the longevity and performance of their MoM hip implants, which underscores the importance of discussion between the surgeon and patient prior to surgery.

In addition to the FDA's 2011 mandate that required postmarket surveillance ("522") studies of MoM total hip replacement systems marketed in the U.S. at the time and launch of the International Consortium of Orthopaedic Registries (ICOR), international regulatory agencies have also issued alerts and safety communications related to MoM hip implants.

• 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 with MoM hip replacements. The recommendations included blood tests and imaging for patients with painful MoM hip implants. In February 2012, MHRA published a medical device alert and updated it in June 2017 with advice on the management and monitoring of patients with MoM hip systems.
• In May 2012 Health Canada issued a communication to orthopaedic surgeons and patients regarding MoM hip implants.
• The Therapeutic Goods Administration of Australia published their safety information for healthcare professionals on MoM hips in September 2012 which was updated in July 2017.

There are also reports in orthopaedic literature, data from international orthopaedic implant registries and presentations from professional/scientific meetings that have increasingly noted complications and potential problems of early failure of MoM hip systems, often requiring revision surgery. Much of the available data are from countries outside the U.S., and the data may not be directly applicable to the experience in the U.S. For example, some of the devices available outside of the U.S. are not marketed in the U.S. For this reason, recommendations from international regulatory agencies may not necessarily apply to U.S. patients with MoM hip systems.

Diagnostic testing (such as soft tissue imaging and metal ion testing) may provide important clinical information for assessing the risks of metal on metal (MoM) hip implants in patients with MoM implants. While the results of these diagnostic tests can be indicative of adverse tissue reactions, they cannot be relied upon as the only sign that a hip is failing.

When conducting soft tissue imaging or metal ion testing in MoM patients, please consider the following:

Soft Tissue Imaging

• For some patients, cross-sectional imaging is required to assess and diagnose potential changes in the soft tissues surrounding an implant.
• The benefits and risks of using different types of diagnostic imaging procedures should be considered when determining the most appropriate imaging modality for each patient.
• MoM hip implants can create metal artifacts (distortions of the image due to the presence of metal in the imaging field) in some imaging modalities.
• The most utilized methods of imaging soft tissue surrounding MoM hip implants include:
  • Magnetic Resonance Imaging (MRI) with metal artifact reduction sequences (MARS)
    • Strengths: MRI uses non-ionizing radiation and offers the best visualization of soft tissues surrounding a MoM hip implant and detection of potential ALTR.
    • Weaknesses: Most MoM hip implants in the U.S. have not been evaluated for safety in an MR environment so the likelihood of adverse events, such as heating of the tissue near the implant, may not be known.
  • Computed Tomography Scan (CT)
    • Strength: CT offers the best visualization of implant positioning and bony tissue
    • Weaknesses: CT uses ionizing radiation and provides lower soft tissue visualization. Image artifacts from the implant may distort the image.
  • Ultrasound
    • Strengths: Ultrasound allows soft tissue visualization without metal artifacts and uses non-ionizing radiation.
    • Weaknesses: Image quality in ultrasound is very operator dependent. Ultrasound provides a lower resolution soft tissue image than MRI and has a limited depth penetration.
• If it is determined that MRI imaging of a MoM hip implant patient is appropriate, the FDA recommends that the orthopaedic surgeon:
  • Consult with the radiologist to evaluate the benefits and risks of utilizing MRI with metal artifact reduction;
  • Use the available device-specific labeling to help determine appropriate scan sequences; and
  • Inform the MRI site that the patient has a MoM hip implant.

Metal Ion Testing

As described in "Concerns about Metal-on-Metal Hip Implants," some patients with a metal-on-metal (MoM) hip implant may have elevated metal ion levels in their bloodstream. These elevated metal ions are predominately cobalt and , chromium, but can also include other metals such as molybdenum and titanium. Depending on the clinical scenario, orthopaedic surgeons may recommend measuring metal ion levels.

Who Should Be Tested?

As part of their overall clinical evaluation, orthopaedic surgeons should consider measurements of metal ion levels in symptomatic patients with MoM hip implants. Serial measurements of metal levels in conjunction with clinical dynamics can help optimizing individual patient management.

• The orthopaedic surgeon should consider testing patients with MoM hip implants who develop any symptoms (hyperlink to the section where the general risks are described) that may indicate that their device may not be functioning properly.
• At the current time, there is insufficient evidence to recommend metal ion testing in patients with MoM hip implants that have none of the signs or symptoms described above and the orthopaedic surgeon feels the hip is functioning properly and has normal radiographs.

What Should Be Tested?

Test Method:

• Measure cobalt using an inductively coupled plasma mass spectrometer (ICP-MS), equipped with either a collision cell or dynamic reaction cell technology, or use a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS). The FDA recommends testing cobalt in EDTA anti-coagulated whole blood using a validated method that meets the Clinical Laboratory Improvement Amendments (CLIA) validation criteria. The method should accurately and precisely measure concentrations as low as 1 µg/L cobalt.
• If chromium is measured, use an ICP-MS, equipped with either a collision cell or dynamic reaction cell technology, or use SF-ICP-MS (in medium or high resolution mode) to resolve potential polyatomic interferences. The FDA recommends testing chromium in EDTA anti-coagulated whole blood using a validated method that meets the CLIA validation criteria. The method should accurately and precisely measure concentrations as low as 1 µg/L chromium.

Selecting a Testing Lab:

• Ensure the lab is CLIA-certified and is using a validated method that meets the CLIA validation criteria for EDTA anti-coagulated whole blood;
• Ensure the lab has an ongoing quality assurance and quality control program for the measurand in EDTA anti-coagulated whole blood;
• Ensure the lab provides collection kits (including all components necessary for sample collection and processing) that are free of significant metal contamination and fit for purpose (i.e., measuring trace and ultra-trace cobalt and chromium). The lab is responsible for validating that all components within the collection kit are not contaminated;
• Ensure the lab participates in a Centers for Medicare and Medicaid Services (CMS) approved trace element proficiency testing (PT) program (e.g. New York State Department of Health, Wadsworth Center) for that particular measurand. A lab's results for that measurand should be within the defined acceptance criteria of the PT program.
• Ensure that the lab has performed an appropriate study, or references appropriate data, to define valid reference range values.

Interpreting Test Results:

• The metal ion concentration values should be considered in addition to the overall clinical scenario including symptoms, physical findings, and other diagnostic results when determining further actions.
• When assessing metal ion concentration values, it is important to determine if the patient has any other reasons to have metal ion concentration values above reference range values including:
  • Other implanted metal hardware
  • Occupational exposure
  • Renal insufficiency
  • Dietary supplements
• Metal ion concentration values should be interpreted in conjunction with blood urea nitrogen (BUN) and creatinine to concurrently evaluate the patient's renal function.
• Test results should be interpreted considering the measurement error of the method and the lab's reference range. The measurement error can be estimated by reviewing the lab's proficiency testing results and the imprecision of the method.
• Ideally, follow test results serially in a patient, ensuring that the same sample type, measurement method and the same laboratory are utilized for each measurement. If a different laboratory was utilized, the ordering physician needs to consider the test results in light of potentially differing laboratory methods that may not have values that are interchangeable. The ordering physician should interpret the test results considering the total error of the method(s) to determine if metal ion levels are changing.

International regulatory agencies developed specific follow-up recommendations for patients with metal-on-metal (MoM) hip implants, including recommendations for blood tests including specific metal ion threshold values. As noted earlier, there are differences between the usage and availability of metal-on-metal hip implants in the U.S. and those outside the U.S., as well as differences in laboratory practices. For this reason, these recommendations may not be appropriate for patients in the U.S. As noted above, several factors can impact the accuracy, reproducibility, and clinical interpretation of the test results.

At the current time, there is not enough evidence in the U.S. demonstrating a correlation between a metal ion level in isolation and the presence of localized lesions, clinical outcomes and/or the need for revision surgery.

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

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?

You should follow-up with your orthopaedic surgeon as recommended. 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, weakness, noise (popping, grinding, clicking or squeaking of your hip), 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, noise, and/or 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?

Local symptoms may include hip/groin pain, weakness, swelling, numbness, or changes in your ability to walk. There can also be systemic symptoms involving the skin, kidney, heart, thyroid, and nervous system. 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 adverse effects that can occur with my metal-on-metal hip implant?

Metal-on-metal hip implants have the same adverse effects as other types of hip implants, including infection, loosening, bone loss, device or bone fracture, and joint dislocation.

In addition, metal particles from a metal-on-metal implant may cause a reaction around the joint, leading to deterioration of the tissue around the joint, loosening of the implant and failure of the device. Metal ions from a metal-on-metal implant will enter the bloodstream. There are case reports in which patients with metal-on-metal hip implants may have developed an adverse reaction to these metal ions and experienced medical problems that could have been related to their implants.

These problems included:

• General hypersensitivity reaction (skin rash)
• Cardiomyopathy
• Neurological changes including sensory changes (auditory, or visual impairments)
• Psychological status change (including depression or cognitive impairment)
• Renal function impairment
• Thyroid dysfunction (including neck discomfort, fatigue, weight gain or feeling cold)

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

The FDA does not know at this time how to predict adverse reactions that may 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, one patient may develop a reaction in response to a very small amount of metal ions in their body, whereas a different patient may have a much larger amount of metal ions in their bodies and yet not react to these ions. Certain patients may have an increased risk of device wear and subsequent local or systemic – reaction and therefore should follow-up with their surgeon more frequently. These patient groups include (but are not limited to):

• Patients with bilateral implants (hip replacements on both the right and left sides)
• Patients with resurfacing systems with small femoral heads (device sizes less than or equal to 44mm)
• Female patients
• Patients receiving high doses of corticosteroids
• Patients with evidence of renal insufficiency (kidney problems)
• Patients with suppressed immune systems
• Patients with suboptimal alignment of device components (device components not placed in the ideal positions)
• Patients with suspected metal sensitivity (e.g. cobalt, chromium, or nickel)
• Patients who are severely overweight
• Patients with high levels of physical activity

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, noise, hip weakness, 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 other evaluations 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 during their evaluation.
3. Report any adverse systemic events which are believed to be related to your metal-on-metal hip implants to the FDA through MedWatch, the FDA Safety Information and Adverse Event Reporting Program.

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 is no evidence to support the need for additional tests. You should continue to routinely follow-up with your orthopaedic surgeon every 1 to 2 years for a physical examination and radiographs.

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

There are case reports of patients with metal-on-metal hip implants who experienced medical problems in areas of the body away from their hip implant. It is possible that these problems may be related to 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 the symptoms related to your skin, heart, nervous system, kidneys, or thyroid gland, it is important that you tell that clinician that you have a 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 is put in its place). Many of these reasons, including infection, dislocation, loosening, 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 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. Post revision hip dislocation has been more prevalent with revision of metal on metal hip replacement.

If I have a revision, what happens to the original implant?

In a revision surgery, your existing hip implant is removed and replaced with another device. Your surgeon may ask you to allow that the implant that was removed to be sent back to the manufacturer for analysis. If you agree, the manufacturer will perform a thorough examination and analysis of the device to better understand how the implant worked and why it may have failed. The analysis is particularly informative in cases where there is no obvious cause of implant failure. Analysis can often lead manufacturers to improve an implant's design and update device labeling for future patients.

In addition to sending the implant, your surgeon will also provide non-personal information about you, the date of the procedure, observations from the revision surgery, and any reports or analysis on the tissue collected during surgery to the hospital pathologist.

There is typically no cost to you for this analysis and you will not be compensated for returning your implant. You may not be notified of the results of the analysis. If you do not want the implant returned to the manufacturer, you may decide what happens to the device.

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

A hip implant 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 recommends 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.

What types of questions should I ask my orthopaedic surgeon about metal-on-metal hip implants?

When discussing your options for hip surgery with your surgeon, some questions you should ask include:

• What are the benefits and risks of each type of hip implant system (metal-on-metal, metal-on-polyethylene, ceramic-on-polyethylene, ceramic-on-ceramic, and ceramic-on-metal total hip systems, as well as, resurfacing versus total hip replacement implants)?
• Why is a metal-on-metal resurfacing hip implant the best for your situation?
• What are the surgeon's results and personal experiences with the recommended hip resurfacing system?
• What are the surgeon's outcomes and personal experience in performing surgical procedures with other types of hip systems?
• What symptoms can you expect to experience after surgery and for how long?
• What types of activities, if any, should be limited or restricted with a metal-on-metal resurfacing hip implant?
• What results can you expect after surgery with a metal-on-metal resurfacing hip implant?
• Which specific symptoms should you report after the surgery?
• What types of reactions may occur due to the implant and/or metal ions and how would they be evaluated and treated?
• If you have a complication related to the metal-on-metal resurfacing hip implant, how likely is it that the implant would need to be removed and what would be the consequences?

Which patients should not have a metal-on-metal hip resurfacing device implanted?

Each type of hip implant has its own set of benefits and risks. Metal-on-metal hip implants 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

What personal information should I share with my orthopaedic surgeon if I am considering a metal-on-metal hip resurfacing 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, tell the surgeon if you have allergic reactions from wearing certain jewelry or from your skin contacting your belt buckle.

What are the risks of having a metal-on-metal hip resurfacing implant?

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 resurfacing implant?

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 or any other type of 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.

Part of the difficulty in answering this question is that individuals vary in how they react to metal ions in their bodies. For example, one patient may develop a reaction in response to a very small amount of metal ions in their body, whereas a different patient may have a much larger amount of metal ions in their bodies and yet not develop a reaction.

Certain patients may have an increased risk of device wear or adverse local tissue reaction (ALTR) and should follow-up with their surgeon more frequently. They include:

• Patients with bilateral implants (hip replacements on both the right and left sides)
• Patients with resurfacing systems with small femoral heads (device sizes less than or equal to 44mm)
• Female patients
• Patients receiving high doses of corticosteroids
• Patients with evidence of renal insufficiency (kidney problems)
• Patients with suppressed immune systems
• Patients with suboptimal alignment of device components (device components not placed in the ideal positions)
• Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
• Patients who are severely overweight
• Patients with high levels of physical activity

Are there any ways to prevent the metal from reaching the joint and bloodstream if I get a metal-on-metal hip resurfacing 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 are released into the joint space and the metal ions may enter the bloodstream. Certain characteristics outlined in the previous question may place patients at risk for increased wear and metal ion production and these patients will need closer follow-up after implantation. Patients will react differently to metal ion levels.

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

Every hip implant has a distinct set of benefits and risks and should be considered on its own merit. The key design features of each implant including size, material, and dimensions make each system unique. In addition, the same hip system will have different outcomes in different patients.

The FDA's assessment of medical devices, including metal-on-metal (MoM) hip implants is based on the, ratio of benefits to risk with the data available. MoM hip implants were designed to offer the following benefits:

• Less device material wear is generated when the ball and socket rub against each other in comparison to other hip implants
• Decreased chance of dislocation when the ball of the thighbone (femur) slips out of its socket in the hip bone (pelvis)
• Decreased chance of device fracture

Although the exact prevalence of adverse local tissue or systemic reactions is not known, for some patients, currently available information supports a favorable benefit-risk ratio.

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

General Recommendations for Orthopaedic Surgeons BEFORE Metal-on-Metal Hip Resurfacing Surgery

• Consider your patient's individual characteristics. Each implant has a unique set of benefits and risks which will result in different outcomes in different patient populations.
• Select a metal-on-metal (MoM) hip resurfacing implant for your patient only after determining that the benefits of using a MoM hip resurfacing implant outweigh the risks, in comparison to using alternative total hip systems (metal-on-polyethylene, ceramic-on-polyethylene, ceramic-on-ceramic or ceramic-on-metal).
  • Members of the FDA's Orthopaedic and Rehabilitation Devices Advisory Panel identified young males with larger femoral heads as the best candidates for MoM hip resurfacing systems.
• Get adequate training in the technical aspects of each individual implant and the surgical instruments needed.
  • The success of MoM hip systems is highly dependent on correct placement and implantation.
  • Contact the manufacturer for device specific information on proper placement.
• Thoroughly review the most recent version of approved manufacturer labeling to determine the contraindications, warnings, and precautions of the device being implanted.
• 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
• When discussing the implant and procedure with the patient, make sure the patient understands:
  • There are hip implants available with different bearing surfaces and each type of hip implant has unique benefits and risks.
  • All hip implants will need to be replaced eventually, and implant longevity is influenced by a patient's age, sex, weight, height, activity level, anatomy, cause of hip pain, and other medical conditions (e.g., overall health, allergies, bone quality, comorbidities). The potential risks associated with MoM hip implants include, but are not limited to:
    • Infection
    • Loosening
    • Dislocation
    • Osteolysis
    • Bone or device fracture
    • Elevated metal ion levels in the joint and blood
    • Transplacental transport of metal ions
    • 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
    • Revision surgery
    • Femoral neck fracture (for hip resurfacing)
  • Certain patients have an increased risk for greater wear of the device or for an adverse local tissue reaction (ALTR) and require closer follow-up. These patients may include:
    • Patients with bilateral implants
    • Patients with resurfacing systems with small femoral heads (less than or equal to 44 mm). Some manufacturers have recalled resurfacing femoral heads of less than or equal to 46 mm.
    • Female patients
    • Patients receiving high doses of corticosteroids
    • Patients with evidence renal insufficiency
    • Patients with suppressed immune systems
    • Patients with suboptimal alignment of device components
    • Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
    • Patients who are severely overweight (BMI >40)
    • Patients with high levels of physical activity
  • Previously implanted hardware at or near the hip joint may increase wear of the device or the amount of metal exposure to the patient who receives a MoM implant or revision.
  • There is currently no evidence to support the use of pre-operative skin patch testing or other tests to predict implant sensitivity prior to surgery.

General Recommendations for Orthopaedic Surgeons DURING Metal-on-Metal Hip Resurfacing Surgery

• Be aware that suboptimal placement may cause excess wear and early failure.
  • Pay particular attention to the angles of inclination and anteversion of the acetabular cup.
  • For resurfacing systems, make sure of appropriate orientation of the femoral stem-shaft angle before cementing into place (all resurfacing femoral heads are intended for cemented use only).
• Do not mix components from different hip implant systems. Each hip implant system has different metallurgy and design specifications and it is imperative that all implanted components and their associated instruments be from the SAME manufacturer's marketed hip implant system.

General Recommendations for Orthopaedic Surgeons AFTER Metal-on-Metal Hip Replacement and Resurfacing Surgery (Follow-up)

• At the time of hospital discharge, schedule the patient for routine office follow-up.
• At the time of hospital discharge, review with the patient or caregiver the signs/symptoms of adverse events.
• The FDA recommends routine long-term follow-up of patients with metal-on-metal (MoM) hip implants, typically to occur every 1 to 2 years.
• If the patient experiences any pain or decreased hip function approximately 3 or more months after surgery, instruct the patient to contact you for a follow-up exam.
• Patient follow-up visits should include:
  • Physical exam with functional assessment, including careful assessment for hip abduction strength to rule out abductor damage
  • Check for asymptomatic local swelling or masses; and
  • Assessment of organs and systems for changes including systemic adverse events in cardiovascular, nervous, endocrine (especially thyroid) and renal systems.
  • Appropriate radiographs to check for implant positioning and osteolysis
• Schedule certain patients with increased risk of device wear or adverse reaction to metal debris (ARMD) for closer follow-up. These may include:
  • Patients with bilateral implants
  • Patients with resurfacing systems with small femoral heads (less than or equal to 44 mm)
  • Female patients
  • Patients receiving high doses of corticosteroids
  • Patients with evidence of renal insufficiency
  • Patients with suppressed immune systems
  • Patients with suboptimal alignment of device components
  • Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
  • Patients who are severely overweight (BMI >40)
  • Patients with high levels of physical activity
• Pay close attention to signs of the following local and systemic symptoms or complications associated with metal-on-metal (MoM) hip implants:
  • Local symptoms or complications:
    • Hypersensitivity (allergic type reaction)
    • Loosening
    • Infection
    • Osteolysis (bone loss)
    • Soft tissue mass or pseudotumor (fluid-filled or solid soft tissue mass around the replaced joint that is diagnosed radiologically)
    • Femoral neck fracture (for resurfacing systems)
  • Systemic symptoms or complications:
    • General hypersensitivity reaction (skin rash)
    • Cardiomyopathy
    • Neurological changes including sensory changes (auditory, or visual impairments)
    • Psychological status change (including depression or cognitive impairment)
    • Renal function impairment
    • Thyroid dysfunction (including neck discomfort, fatigue, weight gain or feeling cold

Follow-Up for Asymptomatic Patients Clinical Evaluation

• If a patient with a metal-on-metal (MoM) hip implant is asymptomatic and has a well-functioning hip, follow-up should occur periodically (typically 1 to 2 years), as with any hip arthroplasty.
• Be aware the following patients may experience increased wear of the implant and/or adverse reaction to metal debris and require closer monitoring. They include:
  • Patients with bilateral implants
  • Patients with resurfacing systems with small femoral heads (less than or equal to 44mm)
  • Female patients
  • Patients receiving high doses of corticosteroids
  • Patients with evidence of renal insufficiency
  • Patients with suppressed immune systems
  • Patients with suboptimal alignment of device components
  • Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
  • Patients who are severely overweight (BMI >40)
  • Patients with high levels of physical activity
• Patient follow-up visits should include:
  • Physical exam with functional assessment; with attention to abductor strength and Trendelenburg test to rule out abductor damage
  • Checking for asymptomatic local swelling or masses; and
  • Assessment for possible systemic adverse events in cardiovascular, nervous, endocrine (especially thyroid) and renal systems.
  • Appropriate radiographs to evaluate for osteolysis or loosening.

Additional Testing for Asymptomatic Patients

• If clinical and imaging data support that the hip prosthesis is functioning properly and the patient is asymptomatic, the FDA is not aware of data which supports the need to routinely check blood metal ion levels or perform soft tissue imaging.
  • Findings of lesions on soft tissue imaging, or of elevated blood metal ion levels in the absence of symptoms have been reported in a limited number of research studies for some MoM hip implant patients. These studies 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 ion levels in isolation and development of potential local or systemic adverse reactions is not well established
  • If the orthopaedic surgeon determines it is in the best interest of the patient to conduct soft tissue imaging, please review the FDA's recommendations.
  • If the orthopaedic surgeon determines it is in the best interest of the patient to test metal ion levels, please review the FDA's recommendations.

Follow-Up for Symptomatic Patients

Clinical Evaluation

• If a patient experiences local symptoms (i.e. pain or swelling at or near the hip, a change in walking ability such as development of Trendelenburg gait, or a noise from the hip joint) more than three months after metal-on-metal (MoM) hip implant surgery, conduct a thorough evaluation, with attention to abductor weakness or Trendelenburg sign to identify abductor damage.
• Follow-up of symptomatic patients with MoM hip implants should occur at least every six months.
• Guide your clinical evaluation by the symptoms and physical findings, including an assessment for well-known and more common emergent complications including joint infection, implant loosening, peri-prosthetic facture and dislocation.
• Recognize that localized lesions associated with reactions to metal debris may also present with pain or a variety signs and symptoms including:
  • Local nerve palsy
  • Palpable mass
  • Local swelling
  • Joint dislocation or subluxation
  • Abductor weakness

Additional Testing for Symptomatic Patients

• In some patients with symptoms, plain radiograph findings (e.g. osteolysis, femoral neck narrowing, component suboptimal positioning, fracture), in conjunction with other non-imaging information, are sufficient to indicate a need for revision surgery.
• In other symptomatic patients, cross-sectional imaging should be considered to diagnose and assess soft tissue findings surrounding an implant.
• Patients with MoM hip implants who develop any symptoms or physical findings that indicate their device may not be functioning properly, should be considered for metal ion testing. (Link to Important Considerations for Metal Ion Testing). It is important to note that at the current time, there is insufficient evidence in the U.S. demonstrating a correlation between a metal ion level in isolation and the presence of localized lesions, clinical outcomes and/or the need for revision surgery.

Assessment for Systemic Effects

• Evaluate patients with new systemic symptoms in collaboration with their primary medical physicians or specialists to determine the cause of their symptoms or findings.
• Patients with evidence of excessive device wear or a localized adverse local tissue reaction (ALTR) should be assessed for potential systemic effects of exposure to metal ions.
  • A thorough physical examination should be performed by the patient's health care team, which include primary medical physicians and/or specialists, with particular focus on cardiovascular, neurological, endocrinological (especially thyroid), and renal systems.
  • Because metal ions are cleared through the kidneys, a patient who has renal insufficiency may be at higher risk for systemic adverse events. Blood urea nitrogen (BUN) and creatinine levels may be measured to evaluate a patient's renal function.

Device Revisions

• At this time, there is not enough evidence to provide a science-based recommendation for a threshold value of metal ion levels in the blood that would serve as a trigger for revision.
• The decision to revise a patient's metal-on-metal (MoM) hip implant should be made in response to the overall clinical scenario and results of diagnostic testing.
  • In extreme cases, adverse local tissue reactions (ALTR) may significantly damage periprosthetic bone, muscle, and nerves. Therefore patients with progressing ALTR, may be considered for earlier revision to prevent extensive damage.
• If you recommend revision, advise patients of the surgical risks of revision as well as the expected outcomes, including:
  • Revision procedures are complicated and may not fully resolve a patient's pain nor restore complete function;
  • In case of ALTR, revision of a MoM hip may have a worse prognosis than revision of other types of bearing surfaces especially for subsequent hip dislocation.
  • Possible need for an additional revision procedure in the future; and
  • Metal ion levels should be expected to decrease after revision.
• In selecting components for revision:
  • Check the specific device labeling for compatibility of device components.
  • Consider the benefits and risks of all bearing surfaces for each patient.
  • If a patient is suspected to have developed metal sensitivity, carefully select the materials of the revision components (potentially avoiding materials with nickel or chromium).
• In order to better understand the performance of these devices and causes of failure, a retrieval analysis is recommended, especially in cases where there is no obvious cause for implant failure such as suboptimal positioning.
  • Talk to the patient about returning the implant for retrieval analysis. A retrieval analysis is a vital part of a manufacturer's quality system allowing them to assess manufacturing and quality processes through their Corrective and Preventative Action (CAPA) system.
  • If the patient agrees, contact the manufacturer prior to revision surgery for instructions on returning the implant for analysis.
  • Along 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.