Hip shape may predict fracture risk
MedWire News: US researchers have shown that the size and shape of the femoral head and neck are important predictors of incident hip fractures.
These findings "suggest that incorporation of geometric measures of hip shape may improve the predictive accuracy of fracture-prediction tools," remark Nancy Lane (University of California-Davis, Sacramento) and colleagues.
The researchers explain that the ability to determine proximal femur shape has been advanced by the development of active shape modeling (ASM). "ASM is a technique [that provides] an average shape for the object being examined as well as principal modes of variation from that shape within the population of interest," they say.
In the current study, Lane and team used ASM to evaluate the relationship between proximal femoral geometry and incident hip fracture among participants of the Study of Osteoporotic Fractures (SOF).
The researchers used ASM of digitized hip radiographs from 168 women who experienced hip fracture during the mean 8.3-year SOF follow-up period and from 231 fracture-free controls, to generate 10 independent "modes of variation" in proximal femur shape.
Taken together, the 10 modes of variation accounted for 95% of the variance in proximal femur shape.
After controlling for age and body mass index (BMI), ASM-derived hip shape demonstrated higher discriminative ability for incident hip fractures than the femoral neck or intertrochanteric bone mineral density (BMD), with area under receiver operating characteristic curve (AUC) values of 0.81, 0.68, and 0.65, respectively.
The best discriminatory ability was obtained by combining ASM hip shape with femoral neck or intertrochanteric BMD to give respective AUCs of 0.84 and 0.83.
Logistic regression modeling of each individual ASM mode showed that hips with more extreme values in ASM mode 4 had the highest risk for incident hip fracture (odds ratio=2.48). This mode was characterized by increased femoral neck length relative to a smaller femoral head size and a narrower femoral neck width and shaft width, note Lane et al.
They conclude in the Journal of Bone and Mineral Research that "the contribution of hip shape to prediction models of fracture is in concordance with several previous studies, highlighting the idea that fracture likelihood depends on a combination of bone mass and bone geometry."
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By Laura Dean