Primary objective : Assessment of the performance of an automatic measurement of vertebral bone mineral density (BMD) on routine abdominal scans for the prediction of fractures (necessitating hospitalization) over 3 years.
Secondary objective :
* Assessment of the performance of an automatic measurement of lumbar vertebral bone density on routine abdominal scans (performed for other medical indications) for the prediction of fractures (necessitating hospitalization) over 3 years according to the location of fracture (spine, hip, non- spine-non-hip).
* Assessment of the performance of an automatic measurement of lumbar vertebral bone density on routine abdominal scans (performed for other medical indications) for the prediction of fractures (necessitating hospitalization) over 3 years according to age (\>= 75 vs \< 75) and sex.
* Assessment of the impact of a preventive treatment of patients at high risk of fracture in terms of number of avoided fractures (simulation study)
* Assessment of classical risk factors of fracture (using SNDS database) and added value of the automatic bone density measurement on fracture risk estimation.
* Prevalence estimation of vertebral fractures (as assessed automatically by the Zebra algorithm) in the population at index date
* Assessment of the impact of IV contrast on the values of the measurements provided by the Zebra algorithm.
* To establish mean values for zebra parameters according to age and gender in subjects without fracture.
The study is based on the patients of the Paris University Hospitals / Assistance Publique - Hôpitaux de Paris (AP-HP), the largest hospital entity in Europe, who had, whatever the medical indication, an abdominal CT; the CT related data (metadata and data issued from the analysis of abdominal CT with the Zebra software) and images are stored in the PACS workstation (available since 2007), and are available through the AP-HP Clinical Data Repository (CDR). After legal authorizations, data from the CDR will be merged with data from the national Programme de Médicalisation des Systèmes d'Information (PMSI) database within the national system of health data SNDS (Système National des Données de Santé), which records all discharge summaries of public and private hospitals in France (i.e. the national PMSI (Programme de Médicalisation des Systèmes d'Information) database) and reimbursed outpatient care (i.e. the DCIR database).
Each summary of the PMSI contains the age and sex of the patient, the motive of admission, described through the diagnosis codes from the International Statistical Classification of Diseases, 10th Revision (ICD-10) and secondary diagnosis, allowing to identify fractures and, among them, neoplastic (on bone metastasis or primary bone cancer) will not be considered as event of interest.
* All legible abdominal scans performed between 2007 and 2014 at AP-HP in subjects of 60 years and older (i.e. those at a priori higher risk of fragility fractures) during a hospital stay and stored on PACS workstation will be used. If a subject performed several abdominal scans, only the first one will be used.
* Vertebral BMD will be calculated automatically with a validated algorithm (in Hounsfield Unit - HU), with the lower attenuation (lower HU) representing less dense bone (i.e. more fragile), at each vertebra from L1 to L4. The algorithm automatically segments the L1-L4 vertebrae, and extracts their overall density based on a number of features extracted. The analysis of abdominal CT with the Zebra software will also identify vertebral fractures.
* Clinical data of APHP patients are available in the CDR.
* Incident fractures will be identified in the national PMSI database within the SNDS (2007-2017). An event will be defined by the occurrence of an incident fracture (excluding polytraumatic fractures and neoplastic fractures) necessitating hospitalization, within 3 years after the abdominal scan.
* Prediction of the occurrence of incident fracture (as defined above) by vertebral BMD will be assessed.
The source population will be patients 60 years and older (i.e. those at a priori higher risk of fragility fractures because of age) who had abdominal QCT with images stored centrally in the Picture Archiving and Communication System (PACS) of our institution (Assistance Publique Hôpitaux de Paris, AP-HP). AP-HP is the largest university hospital entity in Europe (Greater Paris University Hospitals, 39 hospitals, 23 of which are for acute care, 20,700 beds including 11700 beds for acute care, more than 7 million patients treated and 1.2 million hospitalizations each year in acute care). The PACS has been implemented in 2007, and stores all the images acquired in the AP-HP institution and related data. These data are available in the CDR.
After legal authorizations, data from the CDR will be merged with data from the SNDS (Système National des Données de Santé) which includes data from the national Programme de Médicalisation des Systèmes d'Information (PMSI).
