TUESDAY, Sept. 18, 2001 (HealthDayNews) -- Researchers think there's hope for a new way to treat painful osteoarthritis of the knee, but don't expect a traditional tablet or exercise regimen.
Instead, the therapy is brownish-black and three-inches long with suckers on both ends and is better known as Hirudo medicinalis, or the medicinal leech.
German scientists report that in a small pilot study of patients with knee osteoarthritis, leech therapy appeared to substantially reduce pain. Their findings appear In the October issue of the Annals of the Rheumatic Diseases.
"The effect that we have seen, despite the small sample size, is surprisingly clear and very rapid," says lead author Dr. Andreas Michalsen, a senior internist at the Essen-Mitte Clinic in Essen, Germany.
Michalsen enrolled 16 patients, all with knee pain for more than six months. Six declined to be treated with leeches and acted as controls.
Specially trained doctors applied four leeches to the painful knee of the remaining 10 men and women. The leeches were allowed to feed for 80 minutes, during which time they swelled to roughly 5 inches in length.
Although the patients reported the initial bite by the leeches' star-shaped feeding sucker was slightly painful, they had no other side effects or infections.
Patients treated with leeches said their pain began to decline three days after the treatment, falling by day six to an average of 3.4 on a scale ranging from zero to 10, with zero indicating no pain. The pain declined to 1.0 by day 28. Before treatment, the patients rated their pain at 7.
"Compared with other treatments that we do here in our clinic, like aspirin or special physiotherapy, we were very surprised about how intensively this therapy influenced the pain," says Michalsen.
Michalsen says there are two competing theories about what causes the pain of osteoarthritis. Some specialists believe that joint cartilage is responsible, while others suspect that nearby tendons and muscles play a role.
"The leech won't change the joint cartilage -- there's no possibility for that," says Michalsen. "So the leech must influence the structures that are involved in the pain genesis."
He says that the key could be the leeches' saliva. "The leech saliva contains a variety of antiphlogistic [anti-inflammatory] substances," says Michalsen. Nearly 100 such substances have been identified, but which of these may be having an effect is not known, he says.
"The substances can go deep into the tissue," he says.
Sherwin Desser, a professor of parasitology at the University of Toronto, says, "There are a whole series of chemicals released" when a leech bites, including anti-clotting drugs and chemicals that cause the expansion of blood vessels in the area of the bite.
He says evidence indicates that some of the compounds can reduce inflammation.
Michalsen says that while each leech removes about 10 milliliters of blood and lymph per treatment, that effect is minor and not likely the cause of any relief.
But he says there may also be a placebo effect at work. Although initially anxious, patients generally were "delighted" with the procedure, he says.
The enthusiastic response of the patients, many of whom appeared to feel some relief after just a few minutes, has prompted the researchers to plan to measure endorphin levels in subsequent studies to see if these substances, the body's natural painkillers, are responsible for any effect.
Or, he says something called "counter-irritation" might be at work. As with acupuncture, he says a second, minor pain produced at the site of pain overrides the other pain.
However, Michalsen says because the effect appeared to be delayed, a pure drug-related effect might not be involved.
"The effect is stable after four weeks," says Michalsen. The researchers says after initial relief, patients tended to exercise and attend physiotherapy, which may have produced the lasting effects.
Marie Bonazinga, the president Leeches USA, Ltd., of Westbury, N.Y., a major supplier of leeches, says little research has been done on the anti-inflammatory properties of leech therapy. "In the United States, the recognized use for leeches is in plastic surgery and in the reattachment of limbs," she says. The therapy is used for those procedures in case blood doesn't drain properly, she says.
Michalsen says that immune-compromised patients and those with severe Type I diabetes should not be considered for the treatment because they could face a risk of local infections. Also, she says patients with bleeding disorders or those taking anti-coagulant drugs should not undergo the treatment.
The leeches were used only once to prevent the risk of infection. In the past, they generally were destroyed after use, but now, Michalsen says they are shipped to a German biologist who operates a retirement community for medicinal leeches.
What To Do
Leeches have been used to "let out bad blood" for centuries, though the practice fell into disfavor by the mid-19th century.
BioPharm Leeches publishes this FAQ on medicinal leeches. For more detailed information, check the University of Michigan.
If you're not squeamish, check this picture of a medicinal leech feeding on a patient's arm from the University of Paisley.
