Thursday, May 17, 2012

Are Metal-on-Metal Hip Implants Tied to Increased Cancer Risk? Part Two: Health Concerns Related to Metal-on-Metal Hip Implants

How the Ball and Socket Wear

In metal-on-metal implants the metal ball and cup will slide against one another whenever the patient engages in walking, running, or other types of activity. When this happens, tiny metal ions can shave off from the metal implant, entering into the surrounding tissue and even the bloodstream. Even though orthopedic surgeons take special precautions during implantation surgery to optimize the manner in which the ball and socket wear against one another, there is no way to completely avoid the metal ions being released into the body.

As with most substances, different bodies will react to the metal particles in different ways, and there is no way to know which patient will react to the metal or how severe that reaction might be. Over time, however, these particles can damage the bone and tissue surrounding the implant, causing it to loosen and cause chronic pain. In most instances when an adverse reaction occurs, a revision surgery will be required to remove the defective implant and replace it with another. Unfortunately, revision surgery has a lower chance of success, especially if it occurs within a few years of the original implant before the body has had time to recover.

Metal-on-Metal Hip Implants vs. Ceramic and Polyethylene

While the ceramic and polyethylene implants do have a lower rate of revision surgery they may also come with their own issues. Ceramic implants have been known to break inside the body and in 2001 one particular ceramic hip implant device was recalled due to the femoral heads fracturing at a higher than expected rate. The fracturing of a ceramic femoral head can be signaled by sudden pain in the hip joint which is sometimes preceded by a loud “pop.” When a ceramic implant fractures immediate surgery is generally warranted. While the metal-on-metal design is believed to wear out much less quickly than the metal and polyethylene implant, research has indicated no advantages—and many possible disadvantages—of the use of an MOM implant over a metal and polyethylene implant.

Patients Who Should Definitely Avoid the Metal-on-Metal Implant

While all patients who require a hip implant should be guided by their physician’s advice, generally speaking there are several groups of patients who should avoid the MOM implant. Patients who have suffered kidney problems in the past are usually not good candidates for the MOM implant device nor are those with sensitivity to metals or known allergies to metals. Patients with suppressed immune systems or those who are currently receiving high doses of steroid medications such as prednisone are not good candidates for MOM implants and women of childbearing age should avoid the MOM implant due to the possibility of cobalt and chromium leaching into the blood.

Research has shown that metallic ions can cross the barrier from mother to fetus through the placenta and while it has not been determined whether the level is high enough to have an adverse effect on the growing fetus, it is recommended that younger women consider other implant options. Those patients with small body frames may also be at an increased risk of device failure or other adverse events from a metal-on-metal implant. Each hip implant system comes with its own set of benefits and risks, and each design should be looked at carefully.

Health Issues Caused From the MOM Implant

Recipients of the metal-on-metal hip implant may experience hip or groin pain, localized swelling or numbness, infection and joint dislocation as well as noticing changes in their ability to walk normally. In some patients the metal particles can cause a reaction around the joint, leading to tissue deterioration. In more severe instances, patients can experience cobalt poisoning or toxicity. While cobalt is found normally in minute quantities in the body in the form of vitamin B12, the normal level of cobalt in a healthy adult is less than 0.41 micrograms per deciliter in the bloodstream—roughly the same size as one tiny grain of sand. Any level higher than 1 microgram per deciliter can be dangerous, while those above 5 micrograms per deciliter are considered toxic, causing serious health problems.

Workers employed in the metalworking industry may show excessive levels of cobalt in their blood as can nuclear facility workers. Toxic levels of cobalt can lead to heart and lung problems as well as tinnitus, vertigo, atrophy of the optic nerve, constant headaches, cognitive loss, limb weakness, convulsions, hypothyroidism and at extreme levels can cause blindness or deafness. All health care providers are cautioned to be aware of the potential symptoms of cobalt toxicity and to monitor their patients closely for a minimum of five years following implant surgery. Patients who have received a metal-on-metal hip implant device and are experiencing any symptoms of ill health or consistently worsening hip or groin pain should speak to their physician regarding revision surgery.

Risks of Revision Surgery for MOM Hip Implants

Any surgery carries risks, in particular adverse reactions to anesthesia, infection, bleeding and blood clots. Those patients who experienced a local reaction to the implant which affected the soft tissue or surrounding bone quality may have a more difficult time with revision surgery. Hip revision surgeries are lengthy procedures which expose the body to potentially infectious agents, and excessive blood loss can be an issue due to the necessity of a larger incision to remove the first implant. Second implants tend to have a less-secure attachment, therefore are more likely to shift, loosen or break an adjacent bone. Revision surgery generally requires a longer recovery time, leading to patients who are by necessity more sedentary and more likely to develop deep vein thrombosis. Dislocation is also much more common in a revision surgery than in the original implant surgery which can significantly impede subsequent physical therapy efforts.

Author: Sullo & Sullo Attorneys

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