Ulnar-sided wrist pain due to radial bifurcation of the extensor digiti minimi tendon: A case report and literature review.

Stenosing tenosynovitis of the extensor digiti minimi (EDM) without trauma is very rare. We report a 21-year-old woman who presented with dorsoulnar wrist pain during palmar wrist flexion and soft tissue mass at the site of pain. Ultrasonography and magnetic resonance imaging showed a round mass radial to the EDM tendon. Conservative treatment for 3 months failed to improve the patient's pain levels. Intraoperative findings revealed smaller radial slip of the EDM tendon, and bifurcation of these was under the distal portion of the extensor retinaculum (ER). Surgical release of the ER, resection of the smaller slip of the EDM tendon, and tenosynovectomy were performed. Histological examination showed tenosynovitis. At the final follow-up 1 year postoperatively, she was asymptomatic. A literature review suggested that stenosing tenosynovitis of the EDM tendon might be caused by frequent use of the hand with a background history of bifurcation of the EDM tendon.