Trigger Finger

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Trigger Finger

Authors, Editors, Case Information Author: Laura Mattson, DO Affiliation: Mayo Clinic Jacksonville Co Author(s): Raul Rosario-Concepcion, MD Senior Editor: Raul Rosario-Concepcion, MD Clinical Vignette: A 73-year-old right-hand-dominant female presented for months of intermittent triggering and locking of the right fourth finger. Dynamic triggering of the digit was appreciated on exam with active flexion and extension. Type of Probe Used: 3-16 MHz linear hockey-stick transducer Unlabeled Short Axis View of the FDS and FDP Tendons at the MCP Joint Unlabeled short axis view of the of the right 4th flexor digitorum superficialis and flexor digitorum profundus tendons at the level of the metacarpophalangeal joint. Labeled Short Axis View of the FDS and FDP Tendons at the MCP Joint Labeled short axis view of the of the right 4th flexor digitorum superficialis and flexor digitorum profundus tendons at the level of the metacarpophalangeal joint. The A1 pulley is seen in long axis and is indicated by the arrows; the maximal A1 pulley thickness measured 0.75mm (see measuring line for reference on where to measure). Unlabeled Long Axis View of the FDS and FDP Tendons Unlabeled long axis view of the right 4th flexor tendons, short axis view of the A1 pulley. Labeled Long Axis View of the FDS and FDP Tendons Labeled long axis view of the flexor digitorum superficialis and flexor digitorum profundus tendons at the level of the metacarpophalangeal joint. The A1 pulley is seen in short axis and is indicated by the arrows. #5 - Video View Video The flexor tendons of the fourth finger are scanned in short axis from mid palm to the level of the mid-shaft of the proximal phalanx. The flexor digitorum superficialis (FDS) begins volar to the flexor digitorum profundus (FDP) in the midpalm. Immediately distal to the MCPJ, the FDS tendon divides into two but remains volar to the FDP tendon. Thereafter, the FDS tendon slips begin to dive dorsal to the FDP tendon and finally (not pictured) attach to the middle phalanx just distal to the proximal interphalangeal joint. #6 - Video View Video Dynamic imaging of the fourth digit is performed at the level of the metacarpophalangeal joint with passive flexion and extension. The flexor digitorum superficialis (volar) and flexor digitorum profundus (dorsal) tendons are seen in long axis. There is selective hypoechogenicity and thickening of the flexor digitorum superficialis tendon just distal to the region of the A1 pulley. The flexor digitorum profundus tendon appears normal. The flexor tendons have difficulty passing under the A1 pulley with dynamic motion. #7 - Video View Video The flexor tendons of the fourth finger are scanned in long axis at the level of the metacarpophalangeal joint (MCPJ). The A1 pulley lies just volar to the flexor tendons at the level of the MCPJ. A needle is seen traversing distal to proximal to penetrate the flexor tendon sheath, where a mixture of local anesthetic and corticosteroid is injected with excellent intra-sheath flow. Interpretation Image Interpretation: The FDS and FDP tendons are intact from mid palm to distal insertion. The FDS tendon in particular is thickened and hypoechoic just distal to the A1 pulley. With dynamic imaging of flexion and extension of the digit, the tendons, in particular those of the FDS, have difficulty passing under the A1 pulley. The A1 pulley was thickened at 0.75mm. These findings are consistent with stenosing tenosynovitis. Additional dynamic imaging is seen of the therapeutic flexor tendon sheath corticosteroid injection, with excellent intra-sheath flow Teaching Pearl: The A1 pulley can be measured by ultrasound, and thickening supports the diagnosis of trigger finger when paired with clinical catching or locking with finger flexion. The pulley is best assessed in long axis over the metacarpal head while also evaluating for flexor tendon thickening, tenosynovitis, and tendon gliding. A maximal A1 pulley thickness above approximately 0.62 mm has been described as abnormal in sonographic studies. Dynamic imaging during flexion and extension can confirm impaired passage of the FDS/FDP tendons beneath the pulley. References: 1. Spirig A, Juon B, Banz Y, Rieben R, Vogelin E. Correlation between sonographic and in vivo measurement of A1 pulleys in trigger fingers. Ultrasound Med Biol. 2016;42(7):1482-1490. doi:10.1016/j.ultrasmedbio.2016.02.017 2. Guerini H, Pessis E, Theumann N, et al. Sonographic appearance of trigger fingers. J Ultrasound Med. 2008;27(10):1407-1413. doi:10.7863/jum.2008.27.10.1407 3. Bianchi S, Gitto S, Draghi F. Ultrasound features of trigger finger: review of the literature. J Ultrasound Med. 2019;38(12):3141-3154. doi:10.1002/jum.15025
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Authors, Editors, Case Information

Unlabeled Short Axis View of the FDS and FDP Tendons at the MCP Joint

Labeled Short Axis View of the FDS and FDP Tendons at the MCP Joint

Unlabeled Long Axis View of the FDS and FDP Tendons

Labeled Long Axis View of the FDS and FDP Tendons

#5 - Video

#6 - Video

#7 - Video

Interpretation

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