Going Out on a Limb
Nerve surgeon Susan Mackinnon has new ways to save arms and legs
Stand up. Step forward. Bend an elbow. Button your shirt. Feed yourself. They are simple commands, carried from the brain to the legs, arms, and hands by thin white fibers, nerves no thicker than a piece of yarn, impossibly delicate yet incredibly important. Cut them, break them, shred them--a car crash or a sharp piece of broken glass will do it--and a limb hangs helpless.
Don't count on most orthopedic surgeons for help--they'll fix broken bones but not broken nerves. Neurosurgeons? They like to work on the brain and spinal cord. "Peripheral nerves, the ones in the extremities, are orphans in medicine," says Susan Mackinnon, chief of plastic and reconstructive surgery at the School of Medicine at Washington University in St. Louis. "A lot of specialists dabble, but nerves belong to no one."
Actually, they belong to Mackinnon. The 56-year-old surgeon performed the first nerve transplant in 1988, using nerves from a cadaver to restore feeling and movement to a boy's crippled leg, and has devoted her career to nerve repair. It's a huge problem: There are an estimated 360,000 nerve injuries to arms, hands, and shoulders every year, from car and motorcycle accidents, mishaps with power tools and lawnmowers, and even from surgeons setting bones who get a little too close to the vital fibers. (Numbers on leg and foot injuries are not as firm, but doctors think it's well over 100,000.) Often, surgeons recommend amputation to patients with dangling limbs. Yet Mackinnon has worked out ways of not just transplanting nerves from a donor but also rerouting a patient's own healthy nerves into areas left paralyzed by damaged ones. "I can simply take one of their own nerves and move it a little bit to a new place, and let the brain do the rest," she says.
There are now fewer than a dozen surgeons in the United States who mend nerves in this fashion, and "Mackinnon was certainly one of the pioneers," says Andrew Elkwood, chief of plastic and reconstructive surgery at Monmouth Medical Center in New Jersey, who has done nine donor nerve transplants, building on Mackinnon's work. "She's one of the few people who do all kinds of nerve repair, everything from soup to nuts."
Hanging there. The real compliments come from patients. "She's a miracle worker," says Tom Lynn, a 59-year-old print shop owner from Olathe, Kan. Last summer, Lynn was at his lake cottage, grinding down old nails, which were sticking out of boards, using a power drill that had a sharp grinding disk. The disk split. "I clapped my hand to my right shoulder, and four fingers went into a hole," says Lynn. Blood was pouring out. The disk had flown at him, slicing through a major artery and most of the nerves controlling his right arm.
Lynn remembers preparing to die and has vague memories of a helicopter evacuation. Waking up after emergency surgery, "I saw that I still had an arm. But it was just hanging there." Then the pain started: unbelievable, excruciating jolts of agony. Lynn's nerves were shorting and sparking like cut electrical wires. A doctor who knew of Mackinnon's expertise called her for help. Two weeks later she met Lynn. "I honestly didn't know if I could fix it," she says. "It was such a big, ragged injury. But Mr. Lynn looked so awful that I thought we had to try."
Lynn was in surgery the next day. First, there was a patch job. Mackinnon took pieces of a nerve from the back of Lynn's leg--it carries sensation from the back of the heel, something Lynn was willing to sacrifice--and laid them into the gap between the cut nerves in his shoulder. Acting like a trellis, the leg nerve provided support and direction for Lynn's own nerves to regrow from the shoulder back down to the remnants in the arm.
Mackinnon also did some rewiring in Lynn's arm, called a nerve transfer. "It's a tricky idea," she says. "It's like having a broken wire for your kitchen light, but instead of bringing a new wire to it from some central junction box, you run an extension cord in from the nearby pantry, where the wiring still works." For instance, if the nerve that bends the elbow is broken up high, near the shoulder, there's a way around it. There's another nerve nearby that makes a complete run down to the hand. Delicately, Mackinnon can divide that nerve, take a branch, and sew it into the elbow nerve. It takes a while, but the brain eventually learns that the nerve, which used to lead to one muscle, now has branches that lead to two, and it can select which branch to signal. Then it can clench the hand, and also bend the elbow. Surgeons have done transfers for many years, but Mackinnon has come up with new splices, particularly in the upper arm. All Lynn knows is "she gave me my arm back."
That kind of restoration is what Mackinnon has always wanted to do. "I got interested in nerves when I was a med student in Canada studying neurology, back in the 1970s," she says. "Figuring out what was wrong with them was a fabulous intellectual challenge." But diagnosis was a long way from treatment. "We couldn't really do anything for patients," says Mackinnon. "So I switched from neurology to something that had more 'doing': general surgery." That led her to a job at a hospital in Toronto, where she met a neurosurgeon named Alan Hudson who was interested in nerve regrowth. He pushed her to solve the problem. "So I came full circle, back to peripheral nerves. But this time," says Mackinnon, "I could actually do something." It was with Hudson that she did the first nerve transplant.
Excellent results. While transplants get the headlines, "nerve transfers are really where it's at," Mackinnon says. "With transplants, I have to put my patients on immunosuppressive drugs for years so they don't reject the donor nerves, and that's scary. There's too much risk of infection." Hoping to avoid these drugs, Mackinnon runs a lab funded by the National Institutes of Health--one of only a few surgeons to get such support--that's developing methods to neutralize donor nerves so the recipient's immune system doesn't react to them. She does about one donor transplant per year, when a patient doesn't have enough nerve left for any other procedure. But she's much happier doing grafts and transfers. She has performed such transfers on nearly 350 patients over the past decade. "And they have excellent results almost all the time. I'd like to say 'all the time,' but surgeons don't like to jinx themselves," she says. "These people recover normal movement, regain strength, and can use their arms and hands."
But the larger medical community--filled with surgeons who specialize in everything except nerves--has been slow to pick up on this. "The classic teaching is that nerve repairs don't work. Most doctors don't even know new techniques exist," says Elkwood. That ignorance means there are a lot of needless amputations, adds Allan Belzberg, a neurosurgeon and director of peripheral nerve surgery at Johns Hopkins Hospital in Baltimore. "We can save many of these limbs. If I have a message for general surgeons, it's please don't sit on these injuries. Get them to people who can help."
Most often, it's the patients who refuse to be written off who get this aid, says Renata Weber, a plastic and reconstructive surgeon at Montefiore Medical Center in New York City who learned the craft from Mackinnon. "A lot of people do their own searches on the Internet, and they find Susan because she's got an international reputation," she says. Or they find former students like Weber, or Belzberg and the handful of other surgeons who work in this area.
That's not enough for Mackinnon, though. "What we really need is a peripheral nerve center, at a hospital, with a concentration of experts," she says. Weber has come up with a name for the place: the Mackinnon Institute. "But she's too old-school. She's against self-promotion," says Weber. "So the rest of us will have to promote it for her!"
Born: Jan. 31, 1950, in Canada. Education: M.D., Queen's University, Ontario; residencies in general and plastic surgery; fellowships in neurosurgery and hand surgery. Family: married; four children. Books piled near desk: The Mutilated Hand; Hand Surgery, Volume 1; Moo by Jane Smiley
This story appears in the May 8, 2006 print edition of U.S. News & World Report.