This retrospective case series reviewed 9 men and 4 women (mean age, 41 years) with severe post-traumatic elbow arthrosis treated with interposition arthroplasty and temporary hinged external fixation. In 2 patients, treatment was considered to have failed because of early postoperative instability, and their results were classified as poor. The remaining 11 were followed up for a mean of 4 years (range, 1-11 years). The mean arc of flexion improved from 48 degrees before surgery to 110 degrees after surgery. The mean postoperative Broberg-Morrey score was 77 points, reflecting a mean improvement of 41 points (range, 13-68 points) and corresponding with 1 excellent, 4 good, 4 fair, and 4 poor results. Four patients had severe instability associated with bone loss of the distal humerus or trochlear notch. Interposition arthroplasty can improve elbow motion and function but at the expense of elbow stability despite hinged external fixation.