Susan Mackinnon, MD, is a
Washington University nerve
repair specialist and chief of
plastic and reconstructive surgery at
Barnes-Jewish Hospital. And she is
considered an international authority
on nerve regeneration, nerve transfer
and nerve transplant. Mackinnon says,
“When I started my own practice in
1982, I asked a single question:
“How can we improve
results for patients with
nerve injuries?’”
Recently, the answer to that question
came in the form of an innovative
nerve-transfer procedure she
performed that restored some hand
function to a quadriplegic patient.
The patient had sustained spinal cord
injury at the C7 vertebra, the lowest
bone in the neck. Instead of operating
on the spine itself, Mackinnon and a
team of surgeons rerouted working
nerves in the upper arms.
Ida Fox, MD, assistant professor of
plastic and reconstructive surgery at
Washington University, explains the
technique this way: “This procedure
is unusual for treating quadriplegia
because we do not attempt to go
back into the spinal cord where the
injury is. Instead, we go out to where
we know things work—in this case
the elbow—so that we can borrow
nerves there and reroute them to
give hand function.”
Although patients with spinal cord
injuries at the C6 and C7 vertebrae
have no hand function, they do have
shoulder, elbow and some wrist
function because the associated nerves
attach to the spinal cord above the
injury and connect, or “talk,” to the
brain. Since the surgeon must tap into
these working nerves, the procedure
will not benefit patients who have
lost all arm function due to higher
injuries—in vertebrae C1 through C5.
This particular
technique
was originally
developed by
Mackinnon for
patients with arm
injuries specifically damaging the
nerves related to flexion of the thumb
and index finger. This is the first time
she has used nerve transfer to return
limb function after a spinal-cord injury.
Following surgery and a year of
intensive physical therapy, the patient
regained the ability to pinch his
thumb and index finger together.
As a result, he can now feed himself
bite-size pieces of food and write
with assistance. Mackinnon cautions
that the technique does not achieve
instantaneous results. The brain must
be trained to understand that nerves
once used to bend the elbow are now
being called upon to do something
quite different.
Laying the Groundwork
Treatment for nerve injuries has
changed dramatically in the past
30 years. Traditional repair involved
either joining the two severed ends
of the nerve, called direct repair, or
shortening limbs to bring the nerves
together. These techniques put tension
on the nerves, caused scarring and
often yielded poor results.
In the early 1980s, nerve grafting,
using nerves from cadavers, became a
viable option. At that time, Mackinnon
began training with a pioneer in this
procedure: Alan Hudson, MD, chair
of neurosurgery at the University of
Toronto. She spent 10 years perfecting
nerve-graft techniques. “While the
outcomes were better than direct
repair, I was still frustrated by the
results,” she says. “But I learned a lot
in that time and established a great
lab with great people.”
Informed by her research, Mackinnon
began performing her nerve-transfer
technique—a novel procedure for
the time—in 1991. “I received a
lot of push-back from the medical
establishment initially, but I worked
hard and collaborated,” she says.
“As a result, the medical community
around the world has embraced nerve
transfer. It’s now mainstream—but
it’s taken us decades to get here.”
Mackinnon also is one of only a few
surgeons in the United States who
performs brachial plexus surgery,
which involves the complex labyrinth
of nerves branching off the spine at
the base of the neck to the chest.
Currently, Mackinnon is working on
a technique to treat patients with
partial nerve injury. Treatment options
for these patients have been limited
for many years. This promising new
procedure, called supercharge end-toside
transfer (SETS), encourages nerve
regeneration and increases function.
Mackinnon says, “Throughout my
career, I’ve taken the knowledge I
gained from lab research into the
clinic with patients and then from the
clinic back to the lab. This back-andforth
over the years helped me come
up with answers and changed the way
we manage nerve injuries today.”
Sharing Knowledge
Despite advances in treatment,
Mackinnon continues to worry that
many believe not much can be done
for nerve injuries. “We’re just on the
other side of a big shift, but we have a
lot of education to do with doctors and
patients,” she says.
That need for education resulted
in a website designed to train other
physicians in nerve-repair surgery.
“I want all surgeons to get superior
results for their patients, no matter
where they live,” she says.
The still-evolving site, developed by
Ida Fox, MD, and senior research
assistant Andrew Yee, was originally
intended to train military surgeons
who treat the nerve injuries of
American soldiers in Iraq and
Afghanistan. Since its inception, the
website has grown to one that can
help any surgeon anywhere learn the
techniques Mackinnon has pioneered.
Career Highlights
In March, Mackinnon was one of
three physicians in the United States to be honored with the Clinical
Excellence Award by Castle Connolly
Medical Ltd., which publishes
“America’s Top Doctors” and other
guides. Mackinnon says she is most
humbled by being named the recipient
of the 2013 Jacobson Innovation
Award from the American College of
Surgeons. This honor acknowledges
surgeons who have been innovators
of a new development or technique
in surgery. In Mackinnon’s case, it
recognizes her leadership in the field
of nerve regeneration and peripheral
nerve surgery.