With a prevalence of 2 to 3%, trigger finger, also known as stenosing tenosynovitis, is a common hand disorder. Diabetics have a 10-fold higher risk of developing a 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%) aged 52 to 62 years, with the thumb and ring finger predominantly affected [1, 3].
Stenosing tenosynovitis can be recognized as an occupational disease and often occurs when the hand flexors are overstrained (e.g., pianists, athletes, craftsmen, intensive computer work).
Repeated microtrauma causes 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 pulley (annular ligament) and becomes stuck. Patients complain of pain and exhibit the typical snapping phenomenon, locking, and/or loss of active movement of the affected finger [1, 3, 4].
Tumors in the tendons or ganglia can be other, albeit rare, causes of trigger finger. In the majority of cases, trigger finger is the result of repetitive overuse.
The diagnosis is made clinically. A nodular, usually pressure-sensitive thickening of the flexor tendon is palpable at the level of the A1 pulley. The painful snapping phenomenon occurs when the affected finger is flexed and extended. An ultrasound examination can be performed additionally. In case of suspected tumorous change, an MRI examination is helpful, while X-rays are generally unnecessary.
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 the 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 symptoms no longer occur. Modifying practice techniques under the guidance of an experienced (music) therapist represents another conservative treatment option when practicing a musical instrument.
In 1953, Bunnell first reported on 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 long-term. One week after infiltration, patients already notice a reduction in pain, and the snapping phenomenon often subsides after 3 weeks [8, 10].
If the conservative treatment regimen is unsuccessful, surgical release of the annular ligament under local anesthesia, with or without a tourniquet, may be necessary [11]. The success rates of open procedures are 99% [9], with recurrence-free periods of 14.3 years [3].
A minimally invasive percutaneous operation with a special needle was recently published, and long-term results are understandably not yet available [12].