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Hip anatomy linked with atypical hip fracture risk in long-term BP users
DOI:10.1038/bonekey.2014.123
Bisphosphonate (BP) use has long been associated with atypical fractures of the femur; in this study Taormina et al. compared patients on long-term BP therapy who had no hip fracture (n=43), an atypical hip fracture (n=53) or an intertrochanteric hip fracture (n= 64). All patients had a similar duration of BP therapy.
Previous radiographs of the patients were examined to measure the hip-axis length, the neck-shaft angle and the center-edge angle to find possible correlation with fracture risk.
Compared to asymptomatic BP users and BP users with an intertrochanteric hip fracture, those with atypical fractures had a more acute neck-shaft angle (P<0.001), a narrower center-edge angle (P<0.01) and a shorter hip-axis length (P<0.01). Analysis using a logistic regression model using a grouped sample of patients with atypical or intertrochanteric fracture showed a significant association between fracture development and a narrower center-edge angle (OR=0.89, 95% CI=0.80–0.99; P=0.03) and a more acute neck-shaft angle (OR=0.89, 95% CI=0.81–0.97; P=0.01).
Increasing body mass index was also identified as a risk factor for the development of either type of fracture (OR=1.15, 95% CI=1.02–1.31; P=0.03).
Editor’s comment: This is the first controlled study to examine X-ray hip geometry prior to atypical fractures. The results support the hypothesis that the biomechanical loading pattern is different for atypical and intertrochanteric fractures. Unfortunately, bone mineral density data were not reported.
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