Real frequency of ordinary and atypical sub-trochanteric and diaphyseal fractures in France based on X-rays and medical file analysis

PurposeAtypical sub-trochanteric and femoral shaft fractures have been reported in patients treated with bisphosphonates. Their incidence has been determined from registered data analysis using international codes. Therefore, the aim of our study was to estimate the real frequency of typical and atypical sub-trochanteric or diaphyseal fractures, based on radiological and clinical data compared to registered data.MethodsIn the registers of three large French University Hospitals, patients identified with International Classification of Diseases, 10th Revision diagnosis codes for sub-trochanteric or diaphyseal fracture were selected. Frequencies of ordinary and atypical fractures were calculated after both registered data, radiological and clinical files analysis.ResultsAmong the 4592 patients hospitalized for a femoral fracture over 5 years, 574 were identified to have had a sub-trochanteric or femoral shaft fracture. 47.7% of the sub-trochanteric and femoral shaft fractures were misclassified, predominantly in the sub-trochanteric fractures subset. 12 patients had an atypical fracture (4% of the sub-trochanteric and femoral shaft fractures) and 11 fractures presented radiological features of atypical fractures, whereas clinical files analysis revealed they were pathological or traumatic fractures.ConclusionAtypical fractures frequency is very low. Because of their low frequency and the unreliability of registered databases, the risk of atypical fractures is very difficult to estimate retrospectively. A prospective study is needed to clarify the risk factors associated with these fractures.