A reliable method to treat post-amputation pain remains elusive, but a new Northwestern Medicine study conducted in collaboration with Ukrainian physicians suggests that hydro dissection -- a simple procedure that injects fluid around nerves -- may reduce residual limb pain and opioid dependence.

The study is the first to evaluate hydro dissection for post-amputation pain, a condition affecting millions worldwide that is notoriously difficult to treat.

It will be published on Wednesday (Feb. 19) in Regional Anesthesia & Pain Medicine.

"Adding hydro dissection to opioid treatment for post-amputation pain not only appears to improve pain outcomes but also shows mental-health benefits," said senior study author Dr. Steven P. Cohen, a professor of anesthesiology and the vice chair of research and pain medicine at Northwestern University Feinberg School of Medicine.

For young veterans, finding safer alternatives to opioids is especially crucial, said Cohen, a retired U.S. Army colonel who travelled to Ukraine to help set up the study. Many face a high risk of opioid dependence due to severe psychological trauma.

How the study was conducted

Scientists followed 74 Ukrainian soldiers and civilians who had undergone traumatic limb amputations due to war injuries. Thirty-eight patients received hydro dissection alongside opioid therapy within six months of amputation, while 36 received opioids alone.

The study showed that hydro dissection combined with opioids provided better pain relief and reduced opioid use. On a 0-10 pain scale, the hydro dissection group reported an average pain reduction of 4 points, compared to 3 points for those on opioids alone -- a significant difference considered clinically meaningful in most studies.

Additionally, nearly two-thirds of patients in the hydrodissection group reduced their opioid use, while only about one-third of the opioid-only group did. Patients receiving hydrodissection also reported lower anxiety levels. However, its effects on phantom limb pain and chronic pain were more limited.

Findings are 'highly relevant to Americans'

Post-amputation pain is a major challenge for both veterans and civilians worldwide, often preventing amputees from using prosthetics and reducing their quality of life.

An estimated 100,000 Ukrainians have suffered war-related amputations since Russia's full-scale invasion of Ukraine. In the U.S., more than 2 million people live with limb loss, a number that is expected to rise sharply due to ageing populations and increasing rates of diabetes and vascular disease.

"This research is highly relevant to Americans," Cohen said. "Trauma is the leading cause of upper-extremity amputations worldwide, and post-amputation pain affects most amputees, limiting their reintegration into society."

Hydro dissection is remarkably simple

Hydro dissection is an ultrasound-guided procedure where fluid is injected into scar tissues around nerves to relieve pressure, reduce inflammation and promote healing. While the technique has shown promise for acute and neuropathic pain, its effectiveness for post-amputation pain, specifically, had not been previously studied.

"It's remarkable how simple and accessible this technique is -- requiring just an ultrasound and a needle. It can be easily adopted by most community hospitals in the U.S.," said Cohen.

Returning to Ukraine

Given the challenges of conducting research during wartime, the study was exploratory, not controlled. Still, Cohen intends to return to Ukraine this spring to launch new randomised trials focused on novel treatments for post-amputation pain, traumatic brain injury, and PTSD -- undeterred by the dangers of working in a conflict zone.

A veteran of four overseas tours in support of military operations and a father to a son currently serving in the infantry, Cohen is also analysing data on botulinum toxin injections for amputees and examining how mental health factors, such as depression and anxiety, impact phantom limb pain and recovery outcomes.

The other study authors are Dr. Dmytro Dmytriiev who is a pioneer on the use of hydrodissection for postamputation pain, Winnie L. Liu, Dr. Maksym Barsa, Dr. Andreii Khomenko, Dr. Andreii Strokan and Dr. Paul F. Pasquina. This research was partly supported by the U.S. Dept. of Defense and Uniformed Services University, Department of Physical Medicine & Rehabilitation.