Peripheral Nerve Stimulator Implants a New Therapy For Knees

When knee pain persists even following total joint replacement, what's the next step? If stronger drugs and higher doses don't take the edge off the discomfort, are patients left simply having to learn to live with the pain and the limitations it causes in everyday life?

Perhaps not. A therapy that has proven effective in relieving back pain is now bringing a new avenue of relief to patients who suffer from chronic knee pain.

Ty Thomas, MD, of Alabama Pain Physicians, is among the first in the state to implant peripheral nerve stimulators in patients with chronic knee pain who have been unable to find relief in other therapies.

"Knee replacement improves stability, but in some patients, the pain persists," Thomas said. "In the past, we've achieved good results with spinal cord stimulators to ease back pain. This therapy takes a similar approach to knee pain."

Electrodes implanted in the knee near the damaged nerve send pulses of energy to block pain pathways between the nerve and the brain.

"In phase one, we do nerve conduction tests and use an external power source for three to five days as a trial to make sure this therapy can relieve the patient's pain. In some cases, simply breaking the feedback loop has been enough to help patients begin to recover," Thomas said.

"After we see that nerve stimulation is successfully blocking pain signals, we proceed to phase two, where we place the permanent implant through a half-inch incision that is about two centimeters deep. The implant is about the size of a silver dollar, so it is small enough that it usually isn't visible in most patients unless they are unusually thin. The device is similar in some ways to a defibrillator implanted in patients with heart disease.

"The energy source can be recharged through the skin once a week, and patients should continue to get eight to ten years of good use out of it before it needs to be replaced," Thomas said.

For patients with chronic pain, peripheral nerve stimulation offers a strong potential for relief with a relatively low risk of complications and few disadvantages.

"As with any surgery, we have to take care to avoid infection around the incision," Thomas said. "The device may or may not trigger airport scanners, but most people would find that a minor consideration compared to the freedom of being able to go about their lives without the limitations of the kind of pain they experienced before."

Thomas sees treatment possibilities for peripheral nerve stimulation in a growing list of pain syndromes and conditions as the technology develops.

"In addition to spinal cord stimulation for back pain, it can help used to treat hip pain, shoulder pain, and now there's talk of developing an implant for the back of the neck as a possible treatment for fibromyalgia," Thomas said. "That could be a big game changer for a lot of people who are suffering now."

Thomas has already received numerous referrals from primary physicians and orthopaedic surgeons for evaluation of persistent knee pain at his office near Trinity Hospital on Montclair Road. In addition to helping patients after knee replacement surgery, he feels there are additional roles the therapy could play in relieving knee pain.

"It could help patients who need to postpone surgery, and could bring relief to others who aren't good candidates for knee replacement."

As a pain specialist, Thomas see patients with a wide range of conditions causing discomfort that is difficult to resolve through other types of treatment.

"First, we try to identify the pain generator and any amplifiers that are making it worse. In some cases, treatment is straightforward, and we can simply zap the area with a radio frequency ablation or injection. Other times, the source of the pain can be harder to track down, and we may need to try different approaches to resolve it. I like to have every tool available in my tool box to help patients. Peripheral nerve stimulation is an effective tool." Thomas said. "We don't understand everything about how it works to relieve pain. But it works.