[The Spanish National Hip Fractures Registry (RNFC) and the Minimum Basic Data Set (CMBD) are useful for research on hip fractures: comparison of two registries.]

Objective: National hip fracture registries have been established in several countries and recent publications show that the care process has been audited inspecting the representativeness according to quality standards. The aim of this study was to analyse if the Spanish National Hip Fracture Registry (RNFC) represents the Spanish population aged 75 and older admitted for hip fractures, and to compare its results regarding the care process with the national average, according to the National Inpatient register (Minimum Basic Dataset, CMBD).

Methods: The 2017-2018 National Minimum Basic Dataset (Conjunto Mínimo Básico de Datos, CMBD) was used as reference. For analysis, we included 83,110 cases from the CMBD and 21,130 from the RNFC. Eight common variables of both registries were selected for comparison.

Results: No significant differences were observed in the patient-related common variables (age, sex, type of fracture and fracture side), but statistically significant differences were found in the variables describing the care process (proportion of patients operated, deceased, surgical procedures and postoperative length of stay).

Conclusions: The RNFC, designed as a convenience sample, is also representative of the population of patients aged 75 and older treated for hip fractures in Spain. However, there is a participation bias related to the professionals and the hospitals interested in voluntarily participating in a quality improvement program, which would explain the better results observed in the care process, compared to the national average as collected by the CMBD.