The most common cause of proximal radioulnar synostosis in adults is traumatic, usually after forearm fractures. Disabling complications are mainly loss of rotatory movements of the forearm. Various surgical procedures have been described in the literature to end up in forearm synostosis as a complication. We here presented a rare case of proximal forearm synostosis following a common but improper surgical technique for an olecranon fracture complicated by implant infection. The synostosis was treated by resection and fascia lata interposition graft.