Terri Bryant was working at a cheese factory in 2000 when she injured the delicate, rubbery discs between her spinal bones. That was the start of her chronic pain. Two years later, she had back surgery and started regularly taking fentanyl, a powerful prescription opioid medication. Her pain persisted even after a second surgery in 2009.

In 2012, Bryant enrolled in a clinical trial for a device known as a spinal cord stimulator, designed to alleviate back pain. The experimental device was implanted under the skin at the base of her spine. When turned on, it sends pulses of a mild electric current to the nerve fibers in her spinal cord.

The therapy is known as neuromodulation or neurostimulation, and scientists think it works by interrupting the pain signals that are carried from the nerves to the brain. The idea has been around since the 1960s, but in recent years the technology has undergone rapid innovation. While drug developers are trying to discover new nonaddictive medicine to treat pain, medical device manufacturers are racing to develop smaller, more comfortable implants as well as external devices that don’t require surgery. The stimulator Bryant got, called the Senza System, is one of a growing number of medical devices to treat pain.

Despite Americans’ overall pain remaining the same, the amount of opioids prescribed per person was three times higher in 2015 than in 1999, according to the Centers for Disease Control and Prevention. Meanwhile, an estimated two million people in the U.S. abused prescription opioid pain relievers in 2015. As the use of opioids in the U.S. skyrockets, new medical devices could be a drug-free alternative for some patients. For others already addicted to opioids, this technology may instead help alleviate the pain of withdrawal.

Michael Leong, a pain specialist at the Stanford University School of Medicine, says the benefit of these devices is that when patients use them, they’re able to take fewer drugs or no painkillers at all. That’s appealing to both doctors and patients.

“People are afraid of opioids right now. There’s a stigma. Patients don’t want to be on opioids,” he says.

Bryant, now 52, was one of those patients. She used to worry all the time about getting addicted to opioids, which she took for more than 10 years. “I struggled mentally with taking such high doses of pain medicine,” she says. After getting the spinal cord stimulator, her pain decreased almost immediately and she stopped taking fentanyl.

Before the implant, Bryant’s pain was debilitating. Now, she walks regularly and hardly ever misses work. This summer she traveled to Europe, something she says she wouldn’t have been able to do with her severe back pain.

The first spinal cord stimulator was approved by the U.S. Food and Drug Administration in 1989, and since then, medical device giants Medtronic, Boston Scientific, and St. Jude Medical have dominated the neuromodulation market. Patients use an external remote control to adjust or turn off the stimulation. Over time, these devices have gotten smaller and more comfortable for patients, but they're known to cause a tingling sensation called paresthesia, says Leong.

The device Bryant got is manufactured by a new competitor on the market, California-based Nevro, and gained FDA approval in 2015. In contrast to older spinal cord stimulators, it delivers high-frequency stimulation that can’t be felt by the patient. A two-year study of 198 patients published last year found that the Nevro device was better at relieving back and leg pain compared with traditional spinal cord stimulation devices.

Nagy Mekhail, a pain physician at the Cleveland Clinic, says since these implanted devices require surgery, they have typically been prescribed to patients who have exhausted other types of treatment—like physical therapy, medication, and surgery. “It should not be a last-resort therapy. In some patients, it should be the first choice,” he says.

Patients with chronic pain caused by nerve damage, called neuropathic pain, are most likely to benefit from these devices, Mekhail says. According to Boston Scientific, roughly 50,000 to 60,000 patients in the U.S. get spinal cord stimulators every year.