Surgical skin excisions can create wounds that become distorted by the activity of underlying musculature. This is especially relevant for the animated skin of the neck and face. Traumatic lacerations, including those from car accidents and dog bites, are even more prone to untoward muscle pull.
"Traumatic lacerations usually cross wrinkle lines or relaxed skin tension lines. And these types of wounds are known to heal with less favorable cosmetic results," says the study's lead author, Holger G. Gassner, M.D., an otolaryngologist and a fellow in facial plastic surgery at the University of Washington, Seattle. "A variety of techniques and methods have been used in an attempt to reduce the pull of the underlying musculature, which ultimately distorts the wound."Immobilize
Dr. Gassner, who conducted the study while he was at the Mayo Clinic, Rochester, Minn., relates that he and colleagues believed that the only way to eliminate the negative effect of muscle activity on wound healing would be to stop the muscle from functioning.
"That is where the botulinum toxin came into play," he says. "We looked at (its application) first in an animal model using primates and basically performed symmetric excisions on either side of their foreheads. In this blinded study, we treated one side of their forehead with the botulinum toxin and the other side with saline.
"That showed us that we can immobilize the muscle completely with the botulinum toxin, so that the wound would be physically immobilized and not distorted. It also showed that the botulinum toxin-treated wounds in the primates healed better. The animals were comfortable during the procedure and did not need to be sacrificed at the end of the study."
In the human trial, published in the August 2006 Mayo Clinic Proceedings, Dr. Gassner and colleagues recruited 31 patients with forehead wounds from trauma, such as auto accidents, or from surgery, such as skin cancer excision. They randomly selected patients to receive botulinum toxin type A or saline injections and photographed the patients' wounds at the time of the initial treatment and injection and again six months after initial treatment.
In a blinded fashion, two experienced facial plastic surgeons rated the wounds' appearance on a scale of zero to 10, with 10 being the best outcome.
The researchers averaged the ratings of the two surgeons for a final scar appearance score for each patient's wound and found that the median scores for wounds injected with botulinum toxin type A were 8.9, versus 7.1 for those injected with saline.
Side effects were minimal with the botulinum toxin type A injections, including injection site bruising. The largest potential risk in injecting this botulinum toxin type A in the facial area would be transient paralysis at the injection site.
Cosmetic vs. healing dose
"The technique for injecting traumatic lacerations is similar to the one that we use for cosmetic Botox injections. But that applies to the forehead, mainly," Dr. Gassner says. "Preliminary data show that once you start treating wounds in the lower third of the face (say, around the lips), you need higher dosages of the Botox than what you would use for cosmetic injections."
"That will actually give some weakness around the lip that is transient and well-accepted by the patients who understand the mechanism."
The researchers used a technique where they fanned out from the wound and injected dosages of botulinum toxin type A similar to what they would use to treat wrinkles. For the excisional wounds, they injected the botulinum toxin type A under direct vision into the musculature and treated a diameter of about 2 cm around the wound.
Doctors should be aware of treating these patients if their wounds are in functionally important areas, Dr. Gassner says.