Bone mineral density in the proximal femur and hip fracture type in the elderly

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Abstract
Bone mineral density (BMD) in the contralateral proximal femur in 100 female elderly patients with hip fracture and the 35 controls without hip fracture were investigated using dual-photon absorptiometry. The hip fracture patients were divided into intracapsular fracture (n = 53) and extracapsular fracture (n = 47) groups, and these two groups were further divided into five subgroups according to fracture site: intracapsular fracture type 1 (transcervical fracture, n = 29) and type 2 (subcapital fracture, n = 24); extracapsular fracture type 1 (intertrochanteric line fracture, n = 13), type 2 (pertrochanteric fracture, n = 28), and type 3 (combined type of pertrochanteric and subtrochanteric fracture, n = 6). The intracapsular fracture group showed BMD values similar to those of controls; the extracapsular fracture group showed significantly lower BMD values than controls. When these two were subclassified into five subgroups, different results were seen in terms of BMD value in the proximal femur and fracture types; intracapsular fracture type 1 showed BMD values equivalent to those of controls; on the other hand, type 2 showed significantly lower BMD value than controls, and the BMD distribution in the proximal femur among the extracapsular fracture subgroups 1–3 differed, although all of them showed significantly lower BMD values than controls. The degree of trauma causing the fractures was also assessed according to available anamnestic data, but no significant difference was found in trauma tendency between the intra- and the extracapsular fracture group or among the subgroups in each group. Based on these results, it is suggested that BMD distribution in the proximal femur is involved in determining hip fracture type in the elderly.