It appears that hand exercises might have some effect, too, but the evidence is less solid, according to the review, which was published online January 10th in Arthritis Care and Research.
Dr Ingvild Kjeken and her colleagues at Diakonhjemmet Hospital in Oslo, Norway, had noticed that patients in their clinic found significant pain relief from thumb splints. They were also aware of accumulating research evaluating such splints.
So they decided to summarise the evidence to get a better idea of what might best "reduce symptoms and enhance function in people with hand osteoarthritis," Dr Kjeken told. The researchers identified 12 studies with a total of nearly 500 patients, each testing the effects of hand splints, exercises or a combination of the two.
While "striking" differences in the splints and exercise programs limited the comparisons they could make, Dr Kjeken said they were still able to get some idea of what worked.
Short and rigid day splints, for example, cut hand pain in half after six months of use, according to one high-quality study. Similarly, another study found that hand pain was halved for patients who wore a long and rigid splint every night for one year. Just one month of night use lessened pain by a quarter, Dr Kjeken said.
However, the splints usually didn't improve hand function or strength.
Dr Kjerken said the findings mean that splints have about the same effect on pain as anti-inflammatory drugs. The devices range widely in cost, from about $25 for a prefabricated version to over $100 if it is custom made. Ibuprofen, the most commonly used drug by people with osteoarthritis, runs about $10 a month.
"Whether this is an incremental improvement on the top of what drugs do, or if splinting is enough to keep someone from having to take drugs, is an interesting question which warrants further testing," she added.
It's not clear just how splints reduce pain, although it's possible they act by providing support to inflamed joints or a slowing the development of deformities.
"There is strong evidence that splints reduce hand pain," said Dr Kjeken. "A small splint for pain relief during the day combined with a custom-made and rigid splint for prevention of deformities at night may be an optimal regimen."
Unable to estimate
On the other hand, data on exercises was not as good, leaving the team unable to estimate how well exercise might decrease pain or increase function.
Some weak studies did hint at a potential benefit, and Dr Kjeken highlighted existing recommendations that patients should do repetitions of different exercises to increase both joint mobility and grip strength for a minimum of 20 minutes three times a week.
"Due to the risk of developing deformities in the thumb base joint, one should probably avoid excessive exercises to improve pinch or key grip strength," she said, "and rather include exercises aimed at strengthening the muscles involved in opening the hand to be able to grip larger objects."
"It is important that these treatments are individualised and closely monitored," added Dr Kjeken, "especially in the beginning of the treatment period."
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