Medical implants are man-made devices that are designed to mimic or support natural organs and tissues of the body. One common use of medical implants is for the heart. A pacemaker is a device that sends electrical impulses to help the heart maintain a natural rhythm. An implantable cardioverter defibrillator (ICD) can provide an electrical shock to the heart muscle when the heart can’t stop beating in an abnormal rhythm. A left ventricular assist device (LVAD) helps a weak heart pump blood to the body.

Some implantable medical devices are drug delivery systems. These devices provide a predetermined amount of medication to the body, for purposes like easing pain, controlling diabetes or reducing spasticity. Medical implants, called stimulators, may be used to treat neurological conditions (like deep brain stimulation for Parkinson’s) or control muscle function (like urinary or fecal incontinence).

Some medical implants contain no electronic components. The orthopedic industry has been making artificial joints for many years. Intraocular lenses are commonly used to replace the eye’s natural lens for patients with cataracts. Medical implants are also used in some types of cosmetic and reconstructive surgery.

Medical implants play an important role in restoring or maintaining health and function for many Americans. The research organization, Freedonia Group, estimates sales of medical implants in the U.S. are currently about $23 billion. The demand for the devices is expected to grow by more than 10 percent through 2009.

“Micro-sizing” Medical Implants

Researchers are looking for ways to make medical devices smaller (down to a miniature scale), yet still functional. Bruce Towe, Ph.D., Bioengineering Professor at Arizona State University, says the goal is to develop devices that are small enough to fit inside the needle of a syringe, so they can be injected into the body. He is working on a microstimulator chip, a tiny device that would be implanted near the spinal nerves. An electrode placed on the skin would convert sound energy into electrical impulses, which could stimulate nerves or block nerve impulses. The device may be helpful to control pain, stimulate muscles for rehabilitation, or control neurological conditions, like epilepsy or Parkinson’s disease.

Towe is also working on miniature transmitters. The transmitters would act like medical sensors and be powered by a remote device placed over the body (like a wand). He envisions the development of devices that could internally monitor functions like blood pressure, heart rate and body temperature. The information could be “read” by a hand-held device placed over the skin in the area of the sensor. Patients may be able to monitor many of their own body functions at home. Doctors or emergency medical personnel could also quickly obtain important vital signs from the patient.

Towe says privacy is a concern for some people. However, implantable sensors would only be able to activated and read by a wand placed directly over the body or at a very short distance.

For general information on medical devices, visit the website of the FDA’s Center for Devices and Radiological Health at http://www.fda.gov/cdrh/index.html.