Trigger Finger: Causes, Diagnosis, and Treatment Options
Locking of a finger is characteristic of ‘trigger finger’, also termed stenosing tenosynovitis, which is a benign entity that is treated with corticosteroid injection for symptom resolution. Patients complaining of a snapping finger are typically diagnosed with a trigger finger. These common entities tend to occur more in diabetic patients (2). The incidence of a trigger finger in non-diabetics is 2-3% and rises to 10% in diabetics (2). Hyperglycemia can cause crosslinks to form between the collagen molecules of the flexor tendon leading to the development of a trigger finger (2). Being a female and age greater than 60 years old are also risk factors for developing a trigger finger (5).
A trigger finger is also known as a stenosing tenosynovitis (3). The snapping that occurs with a trigger finger is due to impingement of a hypertrophied flexor tendon sheath as it glides under the A1 pulley (3).
A) Right hand dominant
B) History of diabetes mellitus type II
The diagnosis of a trigger finger is typically a clinical diagnosis. Patients will complain of a painful or stiff finger that may lock with finger flexion (2). Providers should palpate over the A1 pulley at the level of the MCP joint to evaluate for a palpable nodule. Ultrasound can also be used to evaluate the quality of the flexor tendon and pulley. Ultrasound findings seen with a trigger finger include increased flexor tendon thickness, fluid overlying the tendon sheath, thickening of the A1 pulley, and tendon sheath cyst (4).
Figure 1. Thickened tendon (left image) and fluid around the tendon sheath (right image) (4)
The criteria used to describe a trigger finger is called the Quinnell criteria (5). Type 0 is normal movement, Type 1 is uneven movement, Type 2 is actively correctable movement, Type 3 is passively correctable movement, and Type 4 is a fixed deformity (5).
First line treatment for a trigger finger is the use of a nocturnal splint that keeps the MCP joint in extension to 0 degrees (6). If the conservative approach fails, patients are then candidates for corticosteroid injections. Studies have shown that corticosteroid injections provide significant improvement until they plateau at 5 years (1). The success with one injection ranges from 60-80% at one year (8). In patients that fail one injection, a second and third injection are sometimes tried. A study published in The Journal of Hand Surgery looked at the effectiveness of repeat corticosteroid injections. In a cohort of 284 patients, they found that a second injection was only successful in 39% of the patients (1). The remaining patients who required a third injection led to a success rate of 82% with three total injections (1).
Side effects of corticosteroid injections for trigger fingers include hyperglycemia, subcutaneous fat atrophy, cellulitis, and tendon rupture (2). A study done in Hand also looked at outcomes in injections that include cortisone with lidocaine and cortisone alone. They found that both injections had similar outcomes, but the group that did not contain the lidocaine experienced less overall pain (3).
Patients who fail conservative measures are candidates for release of the A1 pulley (2). This can be done via an open procedure or an ultrasound guided release of the A1 pulley (7).
Figure 2. Ultrasound image of the A1 pulley and flexor tendon (7)
A trigger finger, or stenosing tenosynovitis, is a locking or stiffness experienced with finger flexion. Patients should be first treated with a corticosteroid injection due to its low morbidity and possibly second injection if needed. Those patients who fail conservative measures are candidates for A1 pulley release, which has very good outcomes.
By: Gregory Rubin, DO @ rubinsportsmed.com
1) Dardas, Agnes Z., et al. “Long-Term Effectiveness of Repeat Corticosteroid Injections for Trigger Finger.” The Journal of Hand Surgery, vol. 42, no. 4, Apr. 2017, pp. 227–35. PubMed, doi:10.1016/j.jhsa.2017.02.001.
2) Kuczmarski, Alexander S., et al. “Management of Diabetic Trigger Finger.” The Journal of Hand Surgery, vol. 44, no. 2, Feb. 2019, pp. 150–53. PubMed, doi:10.1016/j.jhsa.2018.03.045.
3) Patrinely, J. Randall, et al. “Trigger Finger Corticosteroid Injection With and Without Local Anesthetic: A Randomized, Double-Blind Controlled Trial.” Hand (New York, N.Y.), Nov. 2019, p. 1558944719884663. PubMed, doi:10.1177/1558944719884663.
4) Kim, Hae-Rim, and Sang-Heon Lee. “Ultrasonographic Assessment of Clinically Diagnosed Trigger Fingers.” Rheumatology International, vol. 30, no. 11, Sept. 2010, pp. 1455–58. PubMed, doi:10.1007/s00296-009-1165-3.
5) Sato, Edson S., et al. “Treatment of Trigger Finger: Randomized Clinical Trial Comparing the Methods of Corticosteroid Injection, Percutaneous Release and Open Surgery.” Rheumatology (Oxford, England), vol. 51, no. 1, Jan. 2012, pp. 93–99. PubMed, doi:10.1093/rheumatology/ker315.
6) Huisstede, Bionka M. A., et al. “Multidisciplinary Consensus Guideline for Managing Trigger Finger: Results from the European HANDGUIDE Study.” Physical Therapy, vol. 94, no. 10, Oct. 2014, pp. 1421–33. PubMed, doi:10.2522/ptj.20130135
7) Lapègue, Franck, et al. “US-Guided Percutaneous Release of the Trigger Finger by Using a 21-Gauge Needle: A Prospective Study of 60 Cases.” Radiology, vol. 280, no. 2, Aug. 2016, pp. 493–99. PubMed, doi:10.1148/radiol.2016151886.
8) Wojahn, Robert D., et al. “Long-Term Outcomes Following a Single Corticosteroid Injection for Trigger Finger.” The Journal of Bone and Joint Surgery. American Volume, vol. 96, no. 22, Nov. 2014, pp. 1849–54. PubMed, doi:10.2106/JBJS.N.00004.