As carpal tunnel syndrome becomes increasingly common in the developed world, doctors are trying to find more effective methods to diagnose the syndrome. Carpal tunnel syndrome occurs when the medial nerve, the nerve that runs down the arm, through the wrist and into the hand, becomes inflamed or irritated, usually due to pressure or rubbing from repetitive actions.
In the early 1900s, a doctor named Paul Hoffman discovered that if you tap lightly over superficial nerves, you could cause a pins-and-needles sensation in the area fed by the nerve. This was shown by tapping the so-called funny bone, the ulnar. Other researchers followed and used the technique, but some felt that using it could tell them that there were problems with the nerves, as did Jules Tinel in 1915. He not only noted the results of tapping on the area, but he felt it was important that doctors tell the difference between the tingling sensation and actual pain. Throughout the years, this test became known as Tinel’s test and it became widely used in diagnosing carpal tunnel syndrome after G.S. Phalen did so in the 1950s.
Despite Phalen’s enthusiastic use and promotion of Tinel’s test to diagnose carpal tunnel syndrome, recent studies are questioning how effective it really is, with varying sensitivity rates. One possible reason for this is there exists no standard for the test. Some people use a pencil (eraser end) or their middle finger to tap on the end part of the nerve on the wrist, while others use a tendon hammer on the other side of the wrist. To understand how the accuracy of the testing can vary according to the different techniques, the authors of this study measured the force applied by several doctors while performing the Timel’s test, using three different techniques.
The researchers tested nine doctors: three who were experienced hand and nerve surgeons, three who had only been in practice for three years, and three who were in the latter stages of their training. The subjects were told to use their usual strength and techniques when performing the tests, doing three sets of five strikes per technique. Using specialized machines the researchers measured the striking load of the dominant hand middle finger, striking with the dominant hand index and middle finger together, and the thumb of the dominant hand.
After the researchers compiled the data from the recordings of the Tinel’s tests, they found a wide variety in the findings, depending on which technique was being used among all doctors. According to the article, “All three senior surgeons and one subject from each of the two other groups preferred the single-finger strike.” The others preferred the double-finger strike. The practiced surgeons were most consistent with how much force they used when tapping, coming in at about two pounds of force.
In conclusion, the authors state that there are no standards when it comes to performing the Tinel’s sign and this leads to a great variability in how it is performed, causing significant differences in its accuracy in diagnosing carpal tunnel syndrome.