Trigger finger, also known as stenosing tenosynovitis, occurs when the motion of the tendon that opens and closes the finger is limited, causing the finger to lock or catch as the finger is extended. Symptoms of trigger finger develop when either the ring, middle, or index finger attempts to flex closed while gripping. Instead of a smooth, continual closure, the digit stutters then snaps closed. The closure is frequently associated with pain at the base of the digit on the palm of the hand. Trigger finger can affect the thumb.
The tendons that move the fingers are held in place on the bones by a series of ligaments called pulleys. These ligaments form an arch on the surface of the bone that creates a sort of tunnel for the tendon to run in along the bone. To keep the tendons moving smoothly under the ligaments, the tendons are wrapped in a slippery coating called tenosynovium. The tenosynovium reduces the friction and allows the flexor tendons to glide through the tunnel formed by the pulleys as the hand is used to grasp objects.
The tendon can become irritated as it slips through the tunnel. As it becomes more and more irritated, the tendon may thicken, making its passage through the tunnel more difficult. The tissues that hold the tendon in place may thicken, causing the opening of the tunnel to become smaller. The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create a nodule. Rheumatoid arthritis, partial tendon lacerations, repeated trauma from pistol-gripped power tools, or long hours grasping a steering wheel can cause triggering. Infection or damage to the synovium causes a rounded swelling (the nodule) to form in the tendon. As a result, the tendon becomes momentarily stuck at the mouth of the tunnel as the finger is extended. A pop may be felt as the tendon slips past the tight area. This why pain and catching may be felt as the finger is moved.
Trigger finger is caused by local swelling from inflammation or scarring around the tendons that normally pull the affected digit inward toward the palm (flexion). Usually trigger finger occurs as an isolated condition. Sometimes trigger finger is an associated condition resulting from an underlying illness that causes inflammation of tissues of the hand, such as rheumatoid arthritis. In fact, data presented at the 2005 American College of Rheumatology national meeting suggests that a majority of patients with rheumatoid arthritis have inflammation around the tendons of the palm of the hand that could develop into trigger finger.
Trigger fingers are more common in women than men. They occur most frequently in people who are between the ages of 40 and 60 years of age. Symptoms of trigger finger usually start without any injury. Sometimes, one or more fingers are be involved. The symptoms of trigger finger or thumb include pain and a funny clicking sensation when the finger or thumb is bent. Pain usually occurs when the finger or thumb is bent and straightened. Tenderness usually occurs over the area of the nodule–at the bottom of the finger or thumb. The clicking sensation occurs when the nodule moves through the tunnel formed by the pulley ligaments. With the finger straight, the nodule is at the far edge of the surrounding ligament. When the finger is flexed, the nodule passes under the ligament and causes the clicking sensation. If the nodule becomes too large it may pass under the ligament, but becomes stuck at the near edge. The nodule cannot move back through the tunnel, and the finger is locked in the flexed trigger position.
Stiffness and catching tend to be worse after inactivity, such as when the patient wakes in the morning. Often, finger movement will loosen up with activity. Sometimes, when the tendon breaks free, it may feel like the finger joint is dislocating. In severe cases, the finger cannot be straightened, even with help. Patients with diabetes can have several fingers involved, for example.
The diagnosis of trigger finger and thumb is usually quite obvious on physical examination. Usually a palpable click can be felt as the nodule snaps under the first finger pulley. If the condition is allowed to progress, the nodule may swell to the point where it gets caught and the finger is locked in a bent, or flexed position. No special tests or X-rays are required.
If symptoms are mild, resting the finger may be enough to resolve the problem. Over-the-counter pain medications can be used to relieve the pain. Splints are sometimes used to rest the finger.
A physician may choose to inject a corticosteroid. Sometimes, the improvement is temporary and more than one injection may be needed. Injections are less likely to provide permanent relief when the triggering has been present for a long time, or if when there is an associated medical problem like diabetes.
Trigger finger is not a dangerous condition. The decision whether to proceed with surgery is a personal one, based on how severe the symptoms are. If the finger is stuck in a bent position, surgery may be recommended to prevent permanent stiffness. Surgery will open the pulley that is obstructing the nodule and keeping the tendon from sliding smoothly. This surgery can usually be done as an outpatient procedure.
The surgery can be done using a general anesthetic or a regional anesthetic. A regional anesthetic blocks the nerves going to only a portion of the body. Injection of medications similar to novocaine are used to block the nerves for several hours. This type of anesthesia could be an axillary block (only the arm is asleep) or a wrist block (only the hand is asleep). The surgery can also be performed by simply injecting novocaine around the area of the incision. Then, the skin and fascia are separated so the doctor can see the tendon pulley. Special care is taken not to damage the nearby nerves and blood vessels. The surgeon carefully divides the tendon pulley. Once the tendon pulley has been separated, the skin is sewn together with fine stitches. Usually, the fingers can be moved immediately after surgery.
Most patients won’t need to participate in a formal rehabilitation program unless the finger or thumb was locked for a while before surgery. In these cases, the finger or thumb may not straighten out right away after the surgery. A physical therapist may apply a special brace to get the finger or thumb to straighten. The therapist may also apply heat treatments, soft-tissue massage, and hands-on stretching to help with the range of motion. Physical therapy exercises might be prescribed that will help strengthen and stabilize the muscles and joints in the hand. Other exercises are used to improve fine motor control and dexterity.