Trigger Finger
Part I
What is trigger finger or trigger thumb?
Trigger finger and trigger thumb are some most common conditions I treat. It is due to a swollen part of the tendon at the base of the digit. It can cause a painful popping and clicking in the finger or thumb as the patient flexes or extends the digit. It is very common for this to occur just when you wake up in the morning. If the condition is not treated, it will commonly worsen to the point that you cannot fully straighten the finger (or sometimes cannot flex, although that is less common). The painful popping and clicking is called "triggering" (this is where the name comes from) and the inability to fully straighten is called "locking". To better understand how this happens, look at the illustration below.
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The Palm of the Hand
This is a view of the palm side of the hand. The tendons, shown in white, pass into the finger inside a tendon sheath. This sheath functions to keep the synovial fluid (the "tendon oil") around the tendon. The synovial fluid lubricates the tendon as it moves back and forth in the finger. The beginning of the sheath is called the A1 pulley. Note the digital (finger) artery and nerve. They are very close to the pullies. The illustration below shows an enlarged view of the pulley system. |
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Enlarged View of the Pulley System
This illustration shows the tendon sheath, and shows how it has some thicker regions that are divided into regions. The A1 region is the one that gets involved in trigger finger. There is a similar division, but much simpler, in the thumb.
The purpose of the pullies is to keep the tendons close to the bone (see the smaller illustration above, to the left). As the finger bends (flexes), the pullies prevent the tendons from sagging away from the bone.
In trigger finger, there is some swelling of the tendon, due to a variety of factors, mostly processes of aging. The swollen part of the tendon "pops" under the A1 pulley, causing the finger to "pop" or not bend smoothly. Often the patient thinks it is the joint that is popping, but it is the tendon that moves that joint that is popping. |
Continued on Page 2
Revised 10/7/09
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