TRIGGER FINGER AND THUMB
Tendons on the flexor [palm] side of each digit transmit movement from the forearm muscles to the digit tips. To prevent ‘bowstringing’ they are restrained by a fibrous tunnel. The mouth of the tunnel, at the base of the fingers and thumb, may be subject to innocent thickening and narrowing, which causes blocked movement.
This name is given to the same tendon sheath disorder affecting the thumb [radial] side of the wrist. The symptoms are similar to those of trigger digit.
Blocked movement and pain are the key features of this disorder.
Blocked movement may be partial or complete. Commonly the finger/thumb will bend towards the palm with difficulty and pain, together with a catching sensation. It may become momentarily fixed in this position, only regaining a straight posture if forcibly stretched by the other hand, usually with a more severe sensation of release, jumping or clicking and associated pain.
Symptoms are often worse in the morning or after rest.
With a complete block to movement the finger/thumb may be fixed, either fully flexed or fully extended, and will not yield to forcible stretching by the other hand.
Observation of the affected finger/thumb movement may reveal the catching movement or a fixed posture. Feeling the palm side of the finger base will reveal a thickened nodular and tender point, and the bumping movement may be detected.
The patient history and examination finding are usually diagnostic. Special tests are rarely required.
Alternative possibilities need to be considered. Rheumatoid arthritis can give tendon nodules that block movement. Osteoarthritis can cause joint clicking. Dupuytrens’ disease can cause nodules and fixed finger posture. Other features of these conditions will normally be clear to the trained eye.
Keeping the hand and finger / thumb moving is important to prevent a fixed position developing. Wearing a ‘splint’ to rest the finger is usually not indicated.
Steroid injection into the tendon sheath usually gives benefit especially in modest cases. Often, further treatment will not be needed but a proportion of cases recur and benefit from a further injection or surgery.
Surgery to decompress the tendon sheath relieves symptoms and the disorder. It is done for recurrent or severe cases that are persistent.
This is done under local anaesthetic as a ‘day-case’. Pain on insertion of the anaesthetic injection is modest, and the surgical procedure will be painless.
The narrow part of the tendon sheath is opened. Releasing it causes no harm.
After surgery pain is minimal. Light use and movement exercise are performed from the day of surgery, allowing essential functions to continue.
Discomfort and weakness is usual following surgery but reduces progressively, quickly at first, and often continuing for a few months to a minor degree. Temporary inability to fully bend and straighten the finger is a common sequel to this operation for one to two months.