Proximal extensor mechanism reconstruction: modern principles in zone IX injuries: a case report

Abstract

Zone IX extensor tendon injuries of the forearm are uncommon but complex lesions involving the musculotendinous unit and, frequently, the posterior interosseous nerve, resulting in significant functional impairment despite limited external injury. We present the case of a 27-year-old woman with a sharp laceration to the proximal dorsal forearm causing complete loss of active extension of the second through fifth digits. Surgical exploration confirmed complete transection of the extensor digitorum communis tendons with proximal retraction, which were repaired primarily using U-shaped 3-0 absorbable Vicryl sutures, followed by postoperative immobilization in a functional extension position. A narrative review of the current literature addressing epidemiology, anatomy, imaging, surgical management, suture biomechanics, and rehabilitation of zone IX extensor injuries was also performed. This case highlights that successful management requires comprehensive anatomical assessment, evaluation of posterior interosseous nerve integrity, stable primary repair with appropriate tension, and structured rehabilitation. It also emphasizes the limited evidence available for these injuries and the need for further research on zone-specific epidemiology, rehabilitation protocols, and biological augmentation strategies to optimize functional outcomes.