Department of Spine Surgery, Spine Center, Orthopaedic Hospital Speising, Speisinger Str. 109, 1130, Vienna, Austria. Claudia.Eder@oss.at. Department of Spine Surgery, Spine Center, Orthopaedic Hospital Speising, Speisinger Str. 109, 1130, Vienna, Austria. University of Applied Sciences, Vienna, Austria. Karl Franzens University Graz, Graz, Styria, Austria.