Trigger finger and thumb is a condition affecting the movement of the tendons as they bend the fingers or thumb toward the palm of the hand. This movement is called flexion.

Anatomy

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 top of the bone that creates a tunnel of sorts 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.

Causes

Triggering is usually the result of a thickening in the tendon that forms a nodule. There may also be thickening of the pulley ligament as well. The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create the 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 (nodule) to form in the tendon. Triggering can also be caused by a congenital defect that forms a nodule in the tendon. In this situation, the condition is not usually noticeable until an infant begins to use his or her hands.

Symptoms

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 become stuck at the near edge. The nodule cannot move back through the tunnel, and the finger stays locked in the flexed trigger position.

Diagnosis

The diagnosis of trigger finger and thumb is usually quite obvious on physical examination. Usually there is a palpable click that 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 tests or x-rays are required.

Prevention/Treatments

Unfortunately, there is very little that can be done by the physical therapist once a finger or the thumb has developed triggering. A cortisone injection into the sheath may decrease the inflammation and shrink the nodule to relieve the triggering, but it will probably be short lived.

The usual solution for treating a trigger digit is surgery to open the pulley that is obstructing the nodule and keeping the tendon from sliding smoothly.

This surgery can usually be done on an outpatient basis. The surgery uses either a general anesthetic (where you are put to sleep) or some type of regional anesthetic.

A regional anesthetic is a type of anesthesia where the nerves going to only a portion of the body are blocked. Injections of medications similar to novocaine are used to block the nerves for several hours. This type of anesthesia could be an axillary block (where the arm is asleep) or a wrist block (where only the hand is asleep). The surgery can also be performed by simply injecting novocaine around the area of the incision.

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