How ‘Injectrode’ Could Change Treatment of Chronic Pain

By Pat Anson, PNN Editor

An experimental “injectrode” is showing potential as a new neuromodulation treatment for chronic pain, after the first human clinical trial demonstrated the device’s safety and effectiveness in stimulating nerves in the lower back.

The injectrode is a thin and flexible lead wire that is injected by a needle through the skin and placed near an injured nerve. The wire can then be charged by an externally worn stimulator that sends mild electrical impulses to the nerve to block pain signals.

The injectrode is being developed by Cleveland-based Neuronoff, Inc. as a treatment for many types of chronic pain, such as peripheral nerve pain, phantom limb pain and lower back pain. It all depends on the nerve being targeted.

“You can treat knee pain, shoulder pain, lower back pain by stimulating nerve fibers that are providing proprioceptive input sensory input into the spine and thereby help with a reduction of pain perception,” said Manfred Franke, CEO of Neuronoff, who compares the injectrode wire to a Slinky, a toy once popular with Baby Boomers.

“It’s like a spring, like a Slinky, that’s stuck inside a needle,“ he told PNN. “And when that Slinky comes out of the needle, it folds over and it can conform to the anatomy. If you want to take out the injectrode, all you have to do is pull at any point along its length and then the entire injectrode will come out. Nothing is at risk of being left behind.”

This video produced by Neuronoff demonstrates how the device is injected:

Because the injectrode is easy to install in an out-patient procedure, it could potentially be a low-cost competitor to more invasive neuromodulation devices, such as spinal cord stimulators, and reduce the need for pain medication, steroid injections and procedures such as nerve ablation.

“The injectrode represents a paradigm shift in the field of neuromodulation. Its unique flexible design allows for optimal customization to the patient's anatomy and has the potential to be both a temporary and permanent solution without an internal pulse generator,” said Hesham Elsharkawy, MD, an anesthesiologist and clinical advisor to Neuronoff. “The entire procedure takes just 5-10 minutes, making it highly efficient and accessible for patients seeking relief from chronic pain."

In the investigational pilot study, 10 healthy volunteers had injectrodes placed in their lower back and tested. After 30 days, there were no serious adverse events and the injectrodes were removed without analgesics or sutures.

Because the injectrodes work similarly to transcutaneous electrical nerve stimulators (TENS) already on the market, Franke is hopeful the devices will be cleared by the FDA for marketing without more clinical trials, perhaps as soon as early 2025. The key will being getting insurers to cover the injectrodes, which will cost a few thousand dollars, far less than spinal cord stimulators.

“Which is an advantage to the insurance company. And any advantage that you can provide to the insurance company is a benefit for the patient because you're more likely to be receiving prior approval,” Franke said. “The goal is to be cost efficient enough to the insurance companies, so you can replace repeat drug injections or nerve ablations.”   

In addition to pain, Franke says the electrodes have the potential to treat other medical conditions, such as overactive bladders and hypertension. In tests on animals, the devices significantly lowered blood pressure when they stimulated nerves in the neck.

‘Injectrode’ Could Revolutionize Neuromodulation Pain Treatment

By Pat Anson, PNN Editor

A team of scientists and engineers has developed a flexible electrode that can be injected into the body to stimulate damaged nerves, relieve chronic pain and treat other conditions.

The so-called “injectrode” could revolutionize neuromodulation therapy by eliminating the need for invasive spinal cord stimulators and other surgically implanted medical devices.

Researchers used a liquid silicone base -- similar to surgical glue – and mixed it with small metal particles to make it electrically conductive.

When injected around a nerve and allowed to cure, the injectrode performs much like a metal wire, but remains flexible.

Current neuromodulation treatments often rely on rigid implanted devices that can cost hundreds of thousands of dollars, require complex surgeries to install, and often fail or need to be replaced.

IMAGE COURTESY OF NEURONOFF

"Typical implants are really stiff, and so as the body moves, they wear and tear and break down. Our liquid cures, and the result is much closer to the normal elasticity of tissue. You can actually stretch it and increase its size 150 percent to 200 percent without losing its conductivity," says co-author Kip Ludwig, PhD, a professor of biomedical engineering and neurological surgery at University of Wisconsin-Madison.

“By virtue of its simplicity, the Injectrode has the potential to be less invasive, more robust, and more cost‐effective than traditional electrode designs, which could increase the adoption of neuromodulation therapies for existing and new indications.”

Ludwig and his colleagues reported their findings in the journal Advanced Healthcare Materials.

The injectrode has been tested on laboratory animals to stimulate their nervous systems. It was used in pigs to induce heart rate changes by stimulating the vagus nerve in the neck, an approach that's shown promise for treating heart failure, hypertension, lupus and cluster headaches.

"We essentially went through the standard repertoire of electrochemical tests to show this acts like a standard wire electrode that could be used to stimulate the nerve," says co-author James Trevathan, PhD, a postdoctoral fellow in Ludwig's lab.

Ludwig co-founded Neuronoff, a company based on the injectrode, with Case Western Reserve University biomedical engineering professor Andrew Shoffstall, PhD, and Neuronoff CEO Manfred Franke, PhD. Neuronoff recently secured a $2.1 million grant from the National Institutes of Health to further develop the injectrode to stimulate spinal nerves as a treatment for chronic back pain.

The researchers are testing a scheme in which they inject the fluid around the nerve, then extrude a thin insulated string of the material back to just underneath the surface of the skin, where they inject more of the composite material. Then they can use a basic transcutaneous electrical nerve stimulation (TENS) unit to stimulate the nerve from the surface of the skin.

"We're making a bypass from the surface of the skin to the location we want to stimulate," says Ludwig, who envisions using a robotic surgical system to install the injectrode in a procedure similar to getting a tattoo.

"As we learn more and more about how to interface with the nervous system, we're not limited to what we've implanted through an invasive surgical procedure. We can actually change how we stimulate, how we talk to the nerve, because we're essentially just routing our connection to this deep nerve back to the surface of the skin."

Spinal cord stimulators have some of the worst safety records among medical devices, according to a 2018 report by investigative journalists. Stimulators are often touted as safer alternatives to opioid pain medication, but a review of FDA data found over 500 deaths and 80,000 injuries involving stimulators since 2008. Patients reported being shocked or burned by the devices and many had them removed.