The Auxilium Pharmaceuticals treatment, which is awaiting approval by the US Food and Drug Administration, avoids the need for hand surgery and the long rehabilitation that follows.
"It's going to mean they have an option to have this cared for without an operation, and that's never been available before," said Dr Lawrence Hurst of the State University of New York at Stony Brook, whose study appears in the New England Journal of Medicine.
The progressive condition, caused by a growth of collagen nodules in the palm and fingers, afflicts as many as 6% of whites, most of them older, male and often from northern Europe. As the collagen thickens, it can pull a finger into a bent position.
How the test was done
Pennsylvania-based Auxilium paid for the study and analysed the data. Hurst and other study authors have financial ties to the company.
He said the success rate of the enzyme, which has a brand name of Xiaflex, is comparable to surgery. The treatment will be evaluated by an FDA advisory panel later this month.
In the test, the team gave patients up to three treatments, one month apart, to the cord-like obstruction that keeps a finger from straightening.
"The material acts as an enzymatic knife, weakening the collagen of the cord. The next day you come in, and I pull on your finger and break the cord," Hurst said. "The pop can actually be audible sometimes."
It worked in 64% of the joints, compared with 9% of the joints where a placebo was injected instead. Most -- 85% -- of the treated joints showed at least some improvement, versus 12% injected with a placebo.
The pulling was usually done without anaesthesia to see how the treatment worked.
"In the future, I believe we will offer a local (anaesthetic) injection just to make people more comfortable. It is painful, but it is not cruel and inhumane treatment."
The test did not examine whether the problem is likely to recur.
What the tests showed
The technique sometimes produced side effects such as swelling, pain, bruising and, in a few cases, a tear in the skin. There were two cases of tendon ruptures among the 308 volunteers. There were no nerve injuries.
"Joints with less severe contractures were more likely to respond to treatment with collagenase than were joints with more severe contractures, indicating that early intervention may be the most effective treatment approach," the researchers wrote.
Although an operation is now the best treatment, many patients cannot undergo surgery because of their age, a coexisting condition, or both, they said.
Other patients, especially those with early-stage disease, delay surgery or are unwilling to undergo surgery because its risks, the long recovery period and need for physical therapy.
The company is also studying Xiaflex as a treatment for breaking apart collagen deposits that cause penises to bend, a condition known as Peyronie's disease, and for frozen shoulder syndrome.
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