Low-energy diaphyseal femoral fractures associated with bisphosphonate use and severe curved femur: a case series

Recent reports have raised concerns about low-energy subtrochanteric and diaphyseal femoral fractures after long-term bisphosphonate treatment, which may be associated with severely suppressed bone turnover (SSBT). However, diaphyseal femoral fractures without bisphosphonate treatment have also been reported in patients with severely curved femur, which are commonplace in the elderly. The purpose of this study was therefore to investigate associations between occurrence of such fractures, bisphosphonate use, and curvature of the femur. Nine consecutive elderly patients treated for low-energy diaphyseal femoral fractures between 2005 and 2010 were retrospectively reviewed. Three patients sustained bilateral fractures. Eight patients were administered bisphosphonates and one patient was administered raloxifene. Duration of osteoporosis treatment, type of fractures, surgical procedure, cortical thickness and curvature of opposite femur were evaluated. The cortical thickness and femoral curvature were further compared with those of 24 control subjects without fractures. The mean duration of drug administration was 3.6 years. All fractures showed similar X-ray patterns of simple transverse fracture with medial spike. Only one femur showed thickening of the femoral cortex. One case was treated with locking plate fixation, while the other cases were operated with intramedullary nails (9 antegrade nails, 2 retrograde nails). One femur treated with retrograde nail showed delayed bone union. The femoral curvature was significantly higher in the low-energy fracture group than the control group (P < 0.01); however, cortical thickness did not show a significant difference between the groups. In addition to SSBT, increased femoral curvature might be a causative factor for low-energy diaphyseal femoral fracture in the elderly.