The U.S. Food and Drug Administration (FDA) is an agency within the U.S.
Department of Health and Human Services. It consists of the Office of
the Commissioner and four directorates overseeing the core functions of
the agency: Medical Products and Tobacco, Foods and Veterinary Medicine,
Global Regulatory Operations and Policy, and Operations. The following is the
FDA’s position on metal-on-metal hip implants, which have been the subject of several recalls and mass tort litigation
involving major medical device manufacturers such as Stryker, DePuy, Zimmer
Biomet and Smith & Nephew:
All artificial hip implants carry risks including wear of the component
material. Metal-on-metal h(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. Metal can also be released from other
parts of the implant where two implant components connect. Metal release
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 some metal particles.
Different people will react to these metal 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 is sometimes
referred to as an “adverse local tissue reaction (ALTR)” or
an “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.
International regulatory agencies have 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 2012 with advice on the management and monitoring
of patients with MoM hip systems.
In May 2012 Health Canada issued a
public health 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.
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.
If patients with MoM hip implants develop any
symptoms that may indicate that their device is not functioning properly, it is very important for them to make an appointment with their orthopaedic
surgeons promptly for further evaluation. Aside from a physical exam of
the hip, the orthopaedic surgeon may consider several tests to evaluate
these symptoms including:
- Using a needle to remove fluid from around the joint (joint aspiration)
- Soft tissue imaging
- Blood tests, including checking levels of metal ions in the blood
Patients who receive MoM hip implants should also pay close attention to
changes in their general health including new or worsening symptoms outside
their hip. If they are referred to a doctor to evaluate new conditions,
they should let their physician know they have a MoM hip implant. T here
have been some case reports and articles in the medical literature that
suggest patients with a MoM hip implant may have certain symptoms or illnesses
elsewhere in the body (systemic reactions). These include:
- General hypersensitivity reaction (skin rash)
- 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
At the current time, there is not enough evidence to support the routine
need for checking metal ion levels in the blood or soft tissue 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 every 1 to 2 years
to monitor for early signs of change in hip status.