Hannan is a consultant shoulder surgeon in Dublin at the Sports Surgery Clinic, Beaumont Hospital, Cappagh National Orthopaedic Hospital and Blackrock clinic since 2005. He routinely treats elite and professional athletes with particular interest in injuries in Rugby ,Gaelic football and other sports.
He is a founder member of the Irish Shoulder and Elbow society and past president of the society .He was co-president SECEC congress Dublin 2022.
He is an Clinical Associate Professor at RCSI University of Medicine and Health Sciences, Dublin.
He is a member of many international societies including the American Shoulder & Elbow surgery Society, European Shoulder & Elbow Society, German Shoulder & Elbow Society and British Shoulder & Elbow Society .His main research interest currently is in outcomes of shoulder instability treatment particularly in collision athletes. He has over 150 publications in peer reviewed publications. He has completed a PhD thesis on the role of the Latarjet procedure in the athletic population.
He lives in Dublin with his wife and four daughters .