Atypical Trigger Finger Associated With Proximal Flexor Digitorum Superficialis Dynamic Instability Diagnosed With...

Trigger finger is classically attributed to stenosing pathology at the first annular pulley, and the standard diagnostic and therapeutic approach is largely based on that model. However, some patients present with typical triggering symptoms despite normal distal pulley findings on physical examination and static ultrasonography. We report the case of a 25-year-old female cook with painful triggering of the left third and fourth digits. Examination demonstrated reproducible digital catching without focal tenderness over the involved A1 pulleys, whereas focal tenderness was present at the medial elbow near the proximal flexor-pronator region. Plain radiographs were unremarkable. Static ultrasound of the hand showed normal A1 pulleys and no evidence of tendon nodularity or tenosynovitis. Because of the discordance between symptoms and distal imaging, a systematic dynamic ultrasound examination was extended proximally from the hand to the forearm and medial elbow. This examination demonstrated abnormal motion involving the flexor digitorum superficialis near its proximal origin, with a reproducible snap or shift that coincided with the patient's triggering sensation. Ultrasound-guided hydrodissection with 20 mL of 5% dextrose in water was then performed at the site of the dynamic abnormality. Immediate postprocedure dynamic imaging showed smoother tendon excursion and the absence of the previously observed snap or shift, accompanied by prompt symptomatic improvement. At six weeks, the patient had complete resolution of pain, stiffness, and triggering; had returned to full work duties and recreational rock climbing; and repeat dynamic ultrasound showed persistently normalized tendon motion. This case suggests that, in selected patients with clinically typical trigger finger but normal A1 pulley findings, the symptomatic abnormality may be proximal and dynamic rather than distal and stenotic. Dynamic ultrasound may therefore be useful for evaluating atypical trigger finger presentations and guiding targeted, minimally invasive treatment.