Cadaver-based nerve grafts help reduce wound trauma
Last Updated: 87 days ago
SAN FRANCISCO - Christopher Schardt thought he would show off by hopping over a fence at his daughter's day care center last July. But his wedding ring caught on the wire fence, shearing the flesh off his left ring finger as he dropped.
"I looked down at my finger and I could see my bone with the tendons still attached," said Schardt, 49, of Oakland, Calif.
He tested it and found that he could still move it, and then "I grabbed what was left of my finger and went and washed it off, and someone called an ambulance."
Schardt and his exposed finger bone wound up at San Francisco's Buncke Clinic. There, surgeons took a skin graft from his wrist to reconstruct his finger. They also took a vein from the wrist and retrofitted it to function as an artery, bringing in fresh blood to the finger.
But instead of transferring another nerve of Schardt's to rebuild the finger's nerve, they took nerve tissue from a cadaver out of the freezer and inserted that.
The cadaver-based nerve grafts are called allografts, and in some surgeries to repair damaged or severed nerves, they are replacing autografts -- nerve grafts taken directly from a patient, most often from the leg or foot.
Autografts have been used for decades and remain the gold standard for repairing peripheral nerves, doctors said. But allografts are increasingly finding their way into patients' limbs and digits. Most often they help re-grow sensory nerves, but they have been used to repair nerves that control motor function as well.
Allografts, which are provided by a Florida company called AxoGen, come in a variety of sizes up to 7 centimeters and are kept frozen until needed in an operation. The cadavers' cells are removed from the grafts, leaving a protein scaffold to guide the patients' nerves as they re-grow roughly an inch a month.
"With allografts, I get to take the exact size I want," said Dr. Bauback Safa, a surgeon at the Buncke Clinic who worked on Schardt's case. "Within two minutes it's thawed, and I just sew it in."
Other advantages of allografts include avoiding a second surgery in the leg or foot, which can lead to scarring and sensory troubles there. Plus, if the nerve graft gets infected in any way, surgeons can replace the graft and will not have wasted the patient's own nerve tissue.
Researchers have been working to determine whether allografts restore the same level of sensory and motor function as autografts. At this point they have not studied enough patients to show conclusive results.
Questions have been raised about whether allografts are as effective when it comes to motor function as autografts. But a recent study that included Buncke Clinic patients found that allografts up to 5 centimeters produced results similar to autografts.
"Allograft has not been done in enough patients to say that it's the same as autografts, but there are advantages if it ends up being equal," said Dr. Ed Akelman, an orthopedic hand surgeon at Rhode Island Hospital and chairman of the council on education at the American Academy of Orthopaedic Surgeons.
Synthetic conduits do not work as well as human tissue, research has found.
Dr. Gregory Buncke, the director of the Buncke Clinic, said he has seen more and more surgeons embrace allografts since they premiered in 2007. The clinic has been using them since 2008, including on many injuries like Schardt's, which are called ring avulsions.
Buncke said rings are the second most common cause of finger traumas that send patients to the clinic, after saws.
Schardt, a computer programmer who also builds kinetic metal sculptures, got his wedding ring back the day after the fence-jumping attempt, but his finger remains enlarged enough that he cannot slip the ring on.
He has a pin in his finger to help repair a fracture and still has some physical therapy to do to restore flexibility. But in his months of recovery, he has regained feeling in about half of his finger, he said, and is hoping that by July sensation will return all the way to his fingertip.
"In general, my life is not slowed down at all," he said.
(Drew Joseph is a San Francisco Chronicle staff writer. E-mail: firstname.lastname@example.org Twitter: @drewqjoseph)
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