Association of bone mineral density with deformity of the distal radius in low-energy Colles' fractures in Japanese women above 50 years of age

Purpose To investigate whether the degree of radiographically observed pretreatment radius deformity of low-energy Colles' type distal radius fractures resulting from falls is associated with the degree of bone fragility as measured by bone mineral density (BMD) of the lumbar spine in Japanese women above 50 years of age. Methods The study subjects were 125 consecutive Japanese women older than 50 years of age with Colles' type (AO type A and Q dorsally angulated distal radius fractures caused by falls. Fractures due to high-energy injuries such as traffic accidents were excluded. Radius deformity was assessed on anteroposterior and lateral radiographs by measuring ulnar variance, radial inclination, and dorsal angulation at initial examination before manual repositioning of the bone. Bone mineral density of the lumbar spine was also measured by dual energy x-ray absorptiometry at the follow-up visit. Results There were significant differences in the respective values of ulnar variance, radial inclination, and dorsal angulation between patients with BMD values <70% of the mean value of young adults and those with BMD values >= 70%. Radius deformity was significantly greater for all parameters in the former group relative to the latter. The respective values of increased ulnar variance, decreased radial inclination, and increased dorsal angulation significantly correlated with lower BMD. Stepwise regression analysis of data of all subjects identified that ulnar variance was significantly associated with dorsal angulation, BMD, and radial inclination. The addition of body height, body weight, body mass index, and urinary type I collagen cross-linked N-telopeptides (bone resorption marker) to the regression analysis of data of a subset of patients confirmed that ulnar variance was significantly associated with BMD and radial inclination. Conclusions There is a significant association between BMD of the lumbar spine and radiographic radius deformity seen in low-energy Colles' type distal radius fractures resulting from falls in Japanese women above 50 years of age.