Case reports of similar patients treated conservatively demonstrate high morbidity, and, therefore, open reduction and ulnar osteotomy seemed justified. However, this study underlines the importance of minimizing the delay between injury and ulnar osteotomy. If surgery is performed within 40 months after injury, good to fair long-term radiographic results can be obtained. Open reduction and ulnar osteotomy were performed because patients treated conservatively demonstrate high morbidity.