Chronic Medial Dislocation of the Proximal Ulna: A Rare Delayed Complication of a Supracondylar Fracture of the Humerus in Children.

Osteonecrosis of the humeral trochlea is an uncommon but challenging complication of pediatric elbow fractures. We herein report a case of osteonecrosis of the trochlea, a rare and delayed complication of a supracondylar humerus fracture that led to a chronic dislocation of the ulna. A five-year-old boy arrived at the Emergency Room following a fall from a tree on an outstretched hand with an extended elbow. Radiographic studies of the right elbow confirmed the diagnosis of right supracondylar fracture. Open reduction and internal fixation by two Kirschner wires was carried out, followed by immobilization with a long arm cast for six weeks. Five years following surgery, the patient presented with cubitus varus deformity, with no pain or limitation of movement. Radiographic studies showed the presence of osteonecrosis of the humeral trochlea. At the 11-year follow-up consultation, the patient had no complaints, and physical examination of the right elbow showed a limited range of motion for flexion-extension. Radiographic studies showed a medial dislocation of the ulna. The patient was placed on long-term clinical and radiographic follow-up to monitor for secondary osteoarthritis. Our case emphasizes the importance of considering osteonecrosis of the trochlea and ulnar dislocation as delayed complications that can happen following supracondylar humerus fracture in the pediatric population. Clinical and radiologic follow-up are indispensable for diagnosing such a complication at an early stage.