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Figure 1. Tendons & pulleys in hand.
Tendons are the rope-like extension of muscles. They slide in a well-defined channel and attach to a bone to cause joint motion. There are specific sites along the course of a tendon where it is restrained by pulleys to prevent it from "bow stringing." Pulleys are tight bands beneath which the flexor tendons must glide. There is a sheath in between the pulley and the tendon itself. This is a very thin, hollow tube constituting a self-lubricating system. The A-1 pulley can be sacrificed in each finger without side effects because there are 4 more to hold the tendon (Figures 1-3). In fact, only 2 of the 5 in each finger and 2 of the 3 in the thumb are needed for normal function. The thumb has 3 pulleys but only needs 2 for normal motion. The A-1 pulley at the base of the thumb, the metacarpo-phalangeal joint level (MCP), and the A-1 pulley to each of the fingers are overwhelmingly the main location of the problem "trigger finger."
Trigger finger was first described in 1850. Tightening (stenosis) of the first extensor compartment of the wrist was described by Felix de Quervain, a Swiss surgeon, in 1895. This problem is almost identical and more painful. These are among the most common pain-causing conditions of the hand in adults aside.
Careful evaluation of tissue taken from the pulley at the time of surgery for trigger digit reveals that the cause is cellular change (metaplasia) of the pulley. The tendon sheath narrows due to pulley thickening thus reducing the passage diameter. The narrowing causes localized tendon enlargement. This restricts the gliding of the flexor tendon, resulting in the snapping phenomenon, i.e. triggering (Figure 2 & 3). It is unclear whether frequency or the force applied to the tendon contributes to development of a trigger digit. It mostly occurs after age 30. Age and genetics seem to play the greatest role in development. Frequent activity of fingers has not been proven to influence the onset.
At the onset, a patient with trigger finger typically experiences localized discomfort in the palm of the hand at the palmar crease (knuckle level). Local tenderness and sometimes a nodule may be felt if the palm is pressed firmly. In most patients the involved finger or thumb feels swollen. Visible swelling, however, is the exception rather than the rule. One of the most common complaints of trigger digit is stiffness in the morning, which must be separated from possible arthritis. As the day wears on, the feeling of stiffness usually resolves. As the condition progresses, it becomes more painful, ultimately resulting in obvious snapping, getting to a point where one may have to manually straighten or bend the snapping finger with the other functioning hand. It can become too painful to move it through its own normal range of motion.
Trigger Finger Before Treatment
Trigger Finger Surgical Procedure
Triggering or Snapping
The most common triggering occurs in the thumb, second most commonly in the long finger. It can occur in all five digits, either simultaneously or one after the other. Actual triggering or snapping occurs due to the size difference between a tendon and its sheath (Figures 2 & 3).
Trigger thumb occurs in 1 in 1000 infants. Due to an infant's tendency to clasp his thumb in a fist, congenital triggering is not usually picked up until after the sixth month of life. The majority of patients presenting with trigger finger are in their forties or fifties, and about 19% (1 out of 5) of patients have multiple digit involvement. Most adults with trigger digit have or have had carpal tunnel syndrome.
The duration of symptoms prior to receiving any treatment has been shown to effect the rate of success in treatment. It was once thought that this could be treated within a few weeks of onset with a splint limiting MP joint motion, but splinting is ineffective. The problem is not caused by motion. Early treatment with cortisone injection gives variable results though and some can experience lasting relief. How cortisone helps is unknown.
In patients with symptoms for more than a few months duration or patients with severe triggering, and in diabetic patients, cortisone injections are less likely to be effective. Minor sugery is often necessary in this group of patients. Patients with marked triggering and multiple involved digits have a higher rate of failure of non-operative treatment in both groups. Treatment for trigger finger with an injection causes some minor discomfort, it is given into a very sensitive area of the hand, however only one injection is often necessary if it's going to work.
Dr. Ichtertz performs A-1 pulley release almost painlessly on an outpatient basis. There is no blood loss and little risk encountered. Risks include: a rare chance of infection, persistent local tenderness, or pain that may be of greater magnitude than the triggering of the finger (extremely rare). With percutaneous A-1 pulley release for thumb trigger digit, there is a slight chance of nerve injury, thus some may opt for open release of the thumb. Nerve injury with percutaneous finger A-1 release has not been reported.
|Diagram of Percutaneous
A-1 Pulley Release
|Diagram of Flexor Tendon Pulleys|
Some trigger digit patients seen go on to recover without need for surgery. When surgery is undertaken, prognosis is very good. A very small percentage of patients will continue to complain of local tenderness or pain.