Common Hand Disorders in Diabetes
Thickening of tissues in palms and fingers can inhibit movement
Just look at your hands. Go ahead. There's a lot going on down there. The hands are an awesome example of biology at its best: an elaborate biomechanical machine capable of gripping, grabbing, pulling, threading a needle, wielding chopsticks, playing Mozart, and innumerable other delicate procedures.
With all those moving parts—each hand has at least 27 bones (the number can vary among people) and even more joints, plus over 100 ligaments—there's a lot that can go wrong. In the 1950s, researchers first began to recognize that people with diabetes seem to be particularly prone to a constellation of hand disorders. Since then, doctors have learned plenty about these conditions and how to treat them, but there's still much we don't know.
Under the Skin
The most common hand maladies in people with diabetes are carpal tunnel syndrome, trigger finger (stenosing tenosynovitis), limited joint mobility, and Dupuytren's disease (contracture). These conditions are sometimes referred to collectively as cheiroarthropathy. Some experts object to this name, however, because the prefix "cheiro" refers to the hand and these disorders may also affect the shoulder (see "The Shoulder, Too," below).
Each of these four conditions is also found in people without diabetes, but to a lesser extent. According to Arnold-Peter Weiss, MD, professor of orthopedics at Brown University, people with type 1 diabetes are at greater risk for these conditions than those with type 2. Research also suggests that the longer you have diabetes, the greater your risk of developing a hand disorder. At the 2013 American Diabetes Association Scientific Sessions, researchers reported that hand and shoulder disorders affected 2 out of 3 participants in a large study that included people who'd had type 1 diabetes at least 30 years.
Scientists still aren't sure why diabetes increases the risk for hand problems, but there are some theories. The conditions all appear to be related to the overproduction of collagen, a fibrous protein that makes up tendons, joints, ligaments, and other connective tissues in the hand and elsewhere in the body. "One of the best-known problems in diabetes is called collagen glycation," says David Gorman, MSc, PhD, assistant professor of biochemistry and surgery at Western University in London, Ontario, Canada. "In people with diabetes, the collagen can get covered in glucose molecules, which some suspect causes a thickening of the tissue." As you'll see, thickening tissue may be a common thread that links these hand disorders.
Carpal Tunnel Syndrome
Forget what you think you know about office work and carpal tunnel syndrome. "That's a big misconception," says Weiss. "Typing doesn't actually increase the incidence of carpal tunnel syndrome." The condition is caused by a constriction of the hand's central nerve by a ligament that runs across the palm. Diabetes may account for between 5 and 16 percent of all cases of carpal tunnel syndrome. The link between diabetes and carpal tunnel syndrome, according to Weiss, could be that the ligament becomes thickened in response to collagen glycation so that it presses upon the nerve. Another possibility is that diabetic neuropathy—nerve disease—damages the nerves in the hand, making them more susceptible to carpal tunnel syndrome.
Most people with carpal tunnel syndrome have normal use of their hands and fingers, says Weiss. The hallmark of the condition is that people wake up in the middle of the night with numbness or tingling in their fingers, he says, a sensation similar to when a limb "falls asleep." The symptoms occur at night because there is less blood flow to the hand during sleep, and that starves the constricted nerve of nutrients. As the disease progresses, any type of activity that involves holding the hand still for long periods of time, such as driving or talking on a cell phone, can trigger the tingles. Shaking the hand out, to get the blood flowing again, can sometimes reverse the symptoms. Stretching and strengthening exercises may also be helpful; consult a physical therapist. "You can always fix it with surgery. If you get it early enough, steroids and a wrist splint may work, too," says Weiss. He notes, however, that people with diabetes "have a higher failure rate. They end up in surgery a lot more often."
This condition is characterized by a thumb, finger, or fingers that lock in a bent position. The finger straightens with a snap, like a trigger being pulled. It can be painful and, in severe cases, the finger won't straighten at all. The underlying cause of trigger finger is a thickening of the joint at the base of the affected finger, called the A-1 pulley, which is made of collagen. As the A-1 pulley thickens, the tendon has a harder and harder time slipping through it. Eventually it's like "trying to get a 12-foot train through a 10-foot tunnel," says Weiss. The tendon gets stuck, which is why snapping occurs when the finger straightens.
In some people, a steroid injection can solve the problem. Surgery can be effective, too. "You can remove the pulley, which fixes it," says Weiss, adding that people don't really need the A-1 pulley. Some of his patients with diabetes have had that pulley removed from every finger. Again, researchers suspect that collagen glycation drives the thickening of the A-1 pulley.
Limited Joint Mobility
In 1974, Arlan Rosenbloom, MD, now professor emeritus of pediatrics at the University of Florida College of Medicine, described a painless hand condition that he had observed in children between 7 and 18 years old at diabetes camps. Basically, the kids had stiff joints and a permanent bend in the fingers. Today, limited joint mobility is typically screened for by asking patients (children and adults alike) to bring their hands together in a prayer position and spread their fingers. Another screening tool is to see if a person can place palm and fingers, spread wide, flat against a table top. If a bend in the fingers persists, the diagnosis may be limited joint mobility.
A lot has changed in diabetes care since 1974, and Rosenbloom has documented a significant drop in limited joint mobility that correlates with improvements in blood glucose levels. "It's a very solid relationship," says Rosenbloom. The condition is now rare in children. Limited joint mobility is found more often in people with retinopathy and neuropathy, Rosenbloom adds, "so it's not surprising that it's related to [blood glucose] control." Treating limited joint mobility is possible but may not be necessary, as the condition rarely causes a big problem. "There is a surgery, but you'd have to do it in every joint of every finger," says Weiss. "It's not worth the surgery."
Under the skin of the palm is a layer of connective tissue that is extra bouncy. "Because we impact lots of things with our hands … you need a tensioned tissue to protect the underlying tissues," says Gorman. In people with Dupuytren's disease, this tissue begins to thicken. "It resembles scarring," says Gorman, who studies the condition's underlying biological mechanisms. Again, the thickening may be related to an overproduction of collagen because of glycation. There is a genetic component, too. While the affected gene has yet to be identified, Gorman says the condition tends to run in families.
The first sign of Dupuytren's is a "little palpable lump in the hand," says Gorman. "It slowly spreads over the years until it becomes a linear cord that may eventually spread up into the fingers." The condition can be debilitating, leaving a person unable to drive a car or use a knife and fork. The disease is very hard to treat, according to Gorman. "You can have surgery … but recurrence rates are very high." Gorman is working to develop medications to prevent post-surgery recurrence.
As scientists study diabetes-related hand conditions, they may discover new details about how diabetes affects the body more generally. That would be one more reason to thank your hands.
The Shoulder, Too
The union between shoulder and arm, in anatomical terms, is similar to a finger joint. People with diabetes are prone to a disorder of the shoulder joint—called either shoulder-hand syndrome or frozen shoulder—that makes it difficult for the arm to make a full rotation. The condition is similar to hand disorders in which connective tissue thickens and restricts mobility. The connection to diabetes, as with the hand disorders, is believed to be an overproduction of collagen triggered by glycation (attachment of glucose molecules to the tissue).
The hand houses a whopping 27 or more bones. Each finger is animated by an elaborate pulley system consisting of ropelike tendons that snake through eight joints from the palm to the tip of a finger. Having so many joints is what gives us such fine control over the movement of each digit. The tendons are fixed to the underside of the rigid finger bones, so when the hand muscles pull a tendon through the joints, the bones move and the finger bends. Woven throughout the hand is an intricate web of nerves and blood vessels supplying sensation and sustenance to all its moving parts.