The clinical case refers to a male patient, 34 years old, admitted at the Emergency Department after a fall of 2 meters. Of that trauma, resulted an exposed Monteggia fracture type III – Gustillo & Anderson IIA – on his left arm. With this work, the authors intend to describe the evolution of the patient's clinical condition, as well as the surgical procedures he was submitted to. The authors used the patient's records from Hospital's archives, namely from the Emergency Department, Operating Room, Infirmary and Consultation, and also the diagnostic exams performed throughout the patient's clinical evolution. The clinical case began in December 2011, when the patient suffered a fall of 2 meters in his workplace. From the evaluation in the Emergency Department, it was concluded that the patient presented, at the left forearm, an exposed Monteggia type III fracture – Gustillo & Anderson IIA – combined with a comminuted fracture of the radial head. At the admission day, the wound site was thoroughly rinsed, the fracture was reduced and immobilized with an above-the-elbow cast, and antibiotics were initiated. Six days after admission, the patient was submitted to open reduction with internal fixation with plate and screws of the fracture of the ulna and radial head arthroplasty. The postoperative period was uneventful. Two months after the surgical procedure, inflammatory signals appeared with purulent secretion in the ulnar suture. Accordingly, the patient was submitted to fistulectomy, rinsing of the surgical site and a cycle of antibiotics with Vancomycin, directed to the S. aureus isolated from the purulent secretion. The clinical evolution was unfavorable, leading to the appearance of a metaphyseal pseudarthrosis or the ulna and dislocation of the radial head prosthesis. The previously implanted material was therefore removed, 4 months after the traumatic event; at the same time an external fixation device was applied and the first part of a Masquelet Technique was conducted. The second part of the aforementioned procedure was carried out in December 2012. The patient was discharged from the consultation after a 2 years follow-up, with a range of motion of the left elbow acceptable for his daily living activities. In spite of the multiple surgical rinsing procedures and directed antibiotics, the development of a metaphyseal pseudarthrosis of the ulna was inevitable. This clinical case illustrates how the Masquelet Technique presents itself as a good solution for the cases of non-union of fractures in the context of infection.