With a prevalence of 2 to 3%, trigger finger, also known as trigger finger, snapping finger or stenosing tenosynovitis, is a common hand condition. Diabetics have a 10-fold higher risk of developing trigger finger. Amyloidosis, mucopolysaccharidosis, hypothyroidism, gout, renal insufficiency and rheumatoid arthritis are other predisposing conditions [1, 2, 3].
An imbalance between the diameter of the annular ligament and the diameter of the flexor tendon including its tendon sheath is the most common cause of the trigger phenomenon. The condition occurs most frequently in women (75%) between the ages of 52 and 62, with the thumb and ring finger predominantly affected [1, 3].
Stenosing tenosynovitis can be recognized as an occupational disease and occurs frequently when the flexors of the hand are overloaded (e.g., pianists, athletes, craftsmen, intensive PC work).
Repeated microtraumas cause small injuries to the flexor tendons, resulting in an inflammatory reaction and leading to palpable tendon nodules. Once the nodules reach a certain size, the affected flexor tendon can no longer glide through the A1 annular ligament (ligamentum anulare) and gets caught. Patients complain of pain and exhibit the typical snapping phenomenon, catching and/or loss of active movement of the affected finger [1, 3, 4].
Tumors in the tendons or ganglia can be additional, albeit rare causes of trigger finger. In the vast majority of cases, trigger finger is the result of repetitive overuse.
The diagnosis is made clinically. At the level of the A1 annular ligament, a nodular, usually tender thickening of the flexor tendon is palpable. The painful snapping phenomenon occurs when the affected finger is flexed and extended. An ultrasound examination can be performed additionally. If a tumorous change is suspected, an MRI examination is helpful; X-ray images are generally dispensable.
Anti-inflammatory drugs, extension splints [4, 5], physical therapy, trigger point treatment, mobilization and stretching exercises, iontophoresis and shock wave therapy [1, 6, 7, 8] as well as infiltration of the tendon sheath with corticosteroids are considered conservative measures. Triggering factors such as playing instruments, sports and manual activities should be avoided until the symptoms no longer occur. When practicing a musical instrument, modifying the practice techniques under the guidance of an experienced (music) therapist represents another conservative treatment option.
In 1953, Bunnell first reported on a corticosteroid injection for the treatment of trigger finger [9]. During infiltration, a mixture of a local anesthetic and a corticosteroid is carefully instilled into the tendon sheath under sterile conditions (not into the tendon!).
In up to 90% of patients, a 1–2-time infiltration treatment can solve the problem in the long term. One week after the infiltration, patients already notice a reduction in pain, and the snapping phenomenon often subsides after 3 weeks [8, 10].
If the conservative therapy regimen does not lead to success, a surgical annular ligament release under local anesthesia, with or without tourniquet, may be necessary [11]. The success rates of open procedures are 99% [9], with recurrence-free survival at 14.3 years [3].
A minimally invasive percutaneous operation with a special needle was recently published; long-term results are not available as expected [12].