Trigger finger, and also trigger thumb, occurs when a lump forms on the tendon which catches causing a clicking, or triggering, to occur.
There a several stages to trigger finger or thumb. It can start where there is actually not clicking/triggering at all. This is described as pain and nodularity. It is tender over the distal palmar crease (see anatomy section). This pain can be worse on gripping. The nodularity (lumpiness) will move when the finger is moved as the lump is on the tendon which moves. If it doesn’t move it is likely something else.
The stage beyond this is when the tendon actually starts to catch and cause the triggering. This looks like a catch, where the finger jumps when the finger is straghtened. After this stage the finger sticks down and the patient has to try extra hard to straighten it. The final stage is where it’s so stuck that the other hand is used to force the finger straight which is sore!
As such, it is common for people to hold their finger a bit bent so that the lump/nodule on the tendon doesn’t get caught. Unfortunately this can then cause some irreversible stiffness of the Proximal Interphalangeal joint (PIPJ – see anatomy section). This needs to be treated with hand therapy to try and recover the position (get it straight again).
It is often misperceived by sufferers of trigger thumb that the thumb is dislocating at the Interphalangeal Joint (IPJ – see anatomy) – that is the first joint underneath the thumb nail. The problem is actually occuring at the next joint along (further up the arm) but the action of this problem is seen and felt at the IPJ.
Why does it happen?
A nodule / lump forms on the tendon as it goes from the open space in the palm, to the tunnel it runs up in the finger or thumb. The tendons are held up against the bone by pulleys, which are like belt loops. The nodule gets caught on these belt loop like structures and cause the clicking and catching.
Certain groups of patients with problems that thicken the lining of the tendon tunnel have an increased problem with trigger fingers – these include pateints with Diabetes, Rheumatoid arthritis and Gout.
There is no evidence that splints or anti-inflammatories/NSAIDs make a significant difference to the outcome of trigger fingers/thumbs.
Steroid Injections – this involves one injection at the base of the digit of steroid. As an injection into the palm it is unsurprisingly sore. However there is around a 70% cure rate with one injection. This increases to 85% with a second (if the first fails). I don’t give a third as the evidence would imply that it only improves in 5% of people.
The success rates of steroid injections are much lower in diabetics and there is the significant risk of increasing blood sugars with the injection of steroids.
Surgery – this is a local anaesthetic case which takes about 10 minutes of operating. There is a scar in the palm after the surgery and this can take a good 4 months to become managable. There is also a risk of incomplete release, damage to the nerve to the finger of the vessel. There is also the usual risk of bleeding, infection, tender scar, complex regional pain syndrome, initiation of scar tissue in the palm (Dupuytrens type tissue can proliferate after this surgery for some reason).
I don’t personally perform percutaneous trigger release, though the technique is described.