A new Northwestern Medicine study exploring the benefits of targeted muscle reinnervation (TMR) – a series of nerve transfers that permits intuitive control of upper-limb prostheses – could change the way surgical amputations are performed in the future.
The $2.5 million project led by Gregory Dumanian, MD, chief of Plastic Surgery, builds upon his recently published work in Clinical Orthopaedics and Related Research. In that investigation, Dr. Dumanian revealed that 14 of 15 patients suffering from neuroma pain experienced complete resolution of discomfort after TMR. The remaining patient’s pain was improved but not resolved. In several subjects, phantom discomfort from limb loss also improved.
“It was long hypothesized that nerve ends must be sewn together perfectly for any chance of nerve regeneration,” said Dr. Dumanian, professor of Plastic Surgery, Neurological Surgery and Orthopaedic Surgery. “TMR nerves are of greatly different sizes, and so standard nerve surgery wisdom would predict painful neuromas at the coaptation sites. Rather than create more pain for these patients, we discovered that it was improved.”
Post-amputation neuroma pain is somewhat common, affecting up to 25 percent of amputees, and can prevent comfortable prosthesis wear. There aren’t currently any available treatments proven to be consistently effective.
Dr. Dumanian developed the TMR approach in 2002 with Todd A Kuiken, MD, PhD, associate dean for Hospital Academic Affairs at the Rehabilitation Institute of Chicago and a professor of Physical Medicine and Rehabilitation.
“With millions of surgical amputations done each year, painful neuromas are obviously a huge problem,” Dr. Dumanian said. “Pain in an amputated limb is a much bigger problem than improving prosthetic control, as the painful cut nerve endings often prevent effective fitting and use of even the most rudimentary prosthesis.”
The multimillion-dollar surgical trial involves four centers – Walter Reed, San Antonio Military Medical Center, the University of Washington and Northwestern Medicine.
Although Dr. Dumanian’s clinical experience suggests TMR may serve as an effective therapy for post-amputation neuroma pain, this is the first large-scale effort to explicitly study it.
The project will help scientists determine the best way to treat the cut nerve endings in a major limb amputation and simultaneously assess the degree of both chronic local pain from neuromas and phantom discomfort experienced by both upper and lower extremity amputees.
The collaborative effort will rely on a broad-based internet survey, the Patient-Reported Outcomes Measurement Information System (PROMIS), developed by David Cella, PhD, chair of Medical Social Sciences, to compare patient pain perception after standard end-nerve treatments – burying nerve endings deep in surrounding tissue – with perceptions following nerve transfers performed in targeted reinnervation.
“Our findings could influence how every major surgical amputation is performed,” said Dr. Dumanian. “If cut nerve endings in amputees are treated with targeted reinnervation style nerve transfers, and if we can prove that this surgical technique decreases long-term discomfort, then every patient undergoing an amputation may be eligible to undergo this additional procedure at the time of amputation to improve their future quality of life and decrease pain.”
The study is funded by the U.S. Army Medical Research and Materiel Command.