Delayed Rupture of the Extensor Pollicis Longus Tendon following Dorsal Plating of a Distal Radius Fracture in a Rheumatoid Arthritis Patient with Differing Ultrasonographic Findings: A Case Report.

INTRODUCTION: Delayed rupture of the extensor pollicis longus (EPL) tendon is an uncommon but disabling complication following distal radius fracture fixation. The risk is increased in patients with systemic conditions such as rheumatoid arthritis and diabetes mellitus. Although ultrasonography is commonly used for diagnosis, imaging findings may not always correlate with intraoperative observations. CASE REPORT: A 49-year-old female with rheumatoid arthritis and type 2 diabetes mellitus presented with inability to actively extend her left thumb 18 months after dorsal plate fixation of a distal radius fracture. Radiographs demonstrated a united fracture with dorsal plate prominence. Ultrasonography suggested degenerative changes and tenosynovitis of the EPL tendon without clearly demonstrating complete rupture. Owing to persistent clinical suspicion, surgical exploration was undertaken. Intraoperatively, a complete EPL tendon rupture at the level of the extensor retinaculum was identified, with the proximal tendon end not amenable to primary repair. Implant removal followed by extensor indicis proprius (EIP) to EPL tendon transfer using the Pulvertaft weave technique was performed. Following structured post-operative rehabilitation, the patient regained satisfactory thumb extension and hand function by 8 weeks. CONCLUSION: Delayed EPL tendon rupture should be considered in patients presenting with loss of thumb extension after distal radius fracture fixation, particularly in the presence of rheumatoid arthritis or diabetes mellitus. Clinical examination remains paramount, as ultrasonographic findings may underestimate the extent of tendon injury. Timely surgical exploration with implant removal and EIP tendon transfer provides reliable restoration of thumb function.