[Ulnar sesamoid bone of the small finger causing painful trigger finger].

We report on a 38-year-old woman suffering from painful trigger finger. Contrary to the expected intraoperative finding of a simple stenosing pulley and ganglion cyst on a thickened flexor tendon sheath, we found fibrotic cords between an abnormal ulnar sesamoid bone at the fifth finger and the A1-pulley to be responsible for distortion of the tendon sheath and a consecutive "klicking"-phenomenon. A coherence between sesamoid bones and trigger finger has repeatedly been found on the thumb but there is no such description regarding the long fingers.