The DHD was established in 2003. Every department in Denmark, public as well as private,
register all diagnoses, operations and co-operations in the National Patient Registry (NPR). In relation to the NPR every patients are registered with a unique ten-digit number that follows each person throughout life. Detailed information about patient related characteristics, details about different specific operation methods and use of antibiotics, thrombotic prophylactics and tranexamic acid are registered directly in the NPR. Furthermore, any readmission, reoperations or complications, are also registered in NPR, so there are no losses to follow-up. Every year, each department make a local audit of their registered complications, and a larger validation study are currently ongoing in 2015.