Accessory Extensor Pollicis Longus Spanning the Fourth Dorsal Compartment of the Wrist: A Case Report.

Introduction: Variations of the extensor pollicis longus (EPL) tendon of the hand are not uncommon. Yet, this anatomic structure exhibits the least variations among the extensors of the upper extremity. Case Report: This article highlights the presence of an accessory EPL tendon in the fourth dorsal compartment, which was presented as an incidental finding during an elective wrist arthrodesis in a woman in her 40s. Conclusion: Knowledge of this anatomic variation can guide surgical planning and mitigate iatrogenic injury by anticipating potential challenges.