Background Distal radius fracture (fx) is one of the most common osteoporotic fx. Osteoporosis defined as T-score ≤-2.5 SD at spine and/or hip assessed by Dual Energy X-ray (DXA) has been identified as an independent risk factor for distal radius fx . However, a large proportion of fragility distal radius fx occur in patients (∼68%) with T-score > -2.5 . Assessment of bone structure e.g. cortical porosity may improve identification of individuals at high risk of fx . Digital X-ray Radiogrammetry (DXR) used for quantitative measurement of metacarpal cortical hand bone mineral density (BMD) has been shown to predict distal radius fx . This method also provides a quantitative measure of porosity.
Objectives To explore the association between increased cortical hand porosity assessed by DXR and risk of distal radius fx in elderly women.
Methods In this prospective case control study, women with distal radius fx (>50 years) were consecutively recruited from a community hospital. Age-matched controls were randomly identified in the national registry for the same catchment area and invited by mail. A hand radiograph from the non-dominant arm was used for DXR assessment and measurements included: BMD, porosity, cortical thickness and bone width. BMD at lumbar spine (L2-4) and femoral neck was measured by DXA. Statistical tests were applied using SPSS.
Results No significant difference was observed between the 114 distal radius fx patients and the 156 controls for age (67.7 vs 67.2 years, p=0.7), height (164.9 vs 163.8cm, p=0.1) or weight (68.9 vs 71.5 kg, p=0.1) nor for smoking, exercise, use of vitamin-D, bisphosphonates, estrogen or glucocorticoids.
BMD was significantly reduced in fx patients compared with controls both in femoral neck (0.793 vs 0.838 g/cm2, p=0.005) and spine (1.031 vs 1.099 g/cm2, p=0.003) and for DXR hand (0.495 vs 0.522, p=0.003). For the individual components from which DXR BMD is calculated, a significant difference was seen for porosity (0.0124 vs 0.0109, p<0.001) and cortical thickness (0.149 vs 0.160, p=0.002), but not for bone width (0.822 vs 0.811, p=0.055). In univariate regression analysis, expressed as odds ratio (OR), a reduction in the following variables were found to be significantly associated with a distal radius fx: DXR BMD (OR 1.005 per mg, p=0.004), DXA BMD (femoral neck OR 1.003 per mg, p=0.006, spine OR 1.002 per mg, p=0.004) and cortical thickness (OR 1.013 per mm, p=0.002), whereas an increase in porosity was found to be associated with an increased risk of distal radius fx (OR 7.3 per % point increase, p<0.000).
In a multivariate regression model including variables with p<0.2 in the univariate analysis, (DXR BMD and cortical thickness exluded due to linearity) porosity remained significantly associated with distal radius fx (OR 10.08 per % point increase, p=0.001).
Conclusions Our results suggest cortical bone porosity, a measure of bone structure, to play a major role in increasing distal fracture risk in elderly women.
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Oyen et al. Osteoporosis Int 2009
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Disclosure of Interest None Declared