Case Presentation

A 49-year-old right hand-dominant man with no significant medical history presented to the emergency department (ED) with severe right thumb pain. The patient sustained a laceration to the palmar surface of his right thumb 2 days prior to presentation; he did not seek care at that time because the laceration appeared superficial, bleeding was easily controlled and pain was minimal. The patient subsequently developed worsening pain and swelling of his thumb with pain radiating to his right forearm. His pain was exacerbated by any passive or active range of motion of the digit. He took naproxen at home with minimal pain relief, and at the time of presentation to the ED was unable to continue working due to pain. He endorsed subjective fevers and chills but denied any associated neurovascular symptoms, nausea or vomiting.

On examination, the patient held the right thumb in slight flexion, with significant swelling of the entire digit extending to the right thenar eminence. There was minimal associated erythema and no proximal lymphangitic spread. There was a well-healed linear laceration on the medial aspect of the right thumb without any associated discharge, bleeding or dehiscence. There was no palpable crepitus. The range of motion was significantly limited by pain, and the patient had marked tenderness to palpation diffusely, including over his flexor tendon sheath.

X-ray of the right hand showed mild soft tissue swelling around the right thumb but was otherwise unremarkable. Laboratory workup was notable for leucocytosis, with a white blood cell count of 14.4×10⁹/L, and elevated inflammatory markers, with an erythrocyte sedimentation rate of 26 mm/hour (reference range, 0–10 mm/hour) and C reactive protein of 109.5 mg/L (reference range, <7.5 mg/L).

ED point-of-care ultrasound (POCUS) performed by the ED resident and attending physicians showed oedema surrounding the flexor pollicis longus (FPL) tendon, demonstrated by a hypoechoic fluid …