Friederike Schömig1, Jaspaul Gogia2, John Caridi3. 1. Center for Musculoskeletal Surgery, Charité - University Medicine Berlin, Berlin, Germany. 2. Department of Orthopedics, Kaiser Permanente San Jose Medical Center, San Jose, CA, USA. 3. Departments of Neurosurgery and Orthopedics, Mount Sinai Hospital, New York, NY, USA.