Proximal humerus cortical bone thickness correlates with bone mineral density and can clinically rule out osteoporosis
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BACKGROUND: Bone mineral density measurements with dual-energy x-ray absorptiometry (DXA) are commonly used to diagnose osteoporosis and assess fracture risk. This study describes the association between radiographic measures of proximal humeral cortical bone thickness and bone mineral density measured by DXA. The study also assesses the discriminative capability of clinical cortical bone thickness measurements at the proximal humerus to differentiate patients with osteoporosis. METHODS: Patients (N = 108) with shoulder radiographs and DXA studies were evaluated. Cortical bone thickness was assessed with 2 techniques, the gauge method and the average method. Pearson correlations were used to describe the relationship between cortical bone thickness measurement techniques and femoral and lumbar DXA. Sensitivity, specificity, and negative predictive value for predicting osteoporosis were determined for several cortical bone thickness thresholds. Rater reliability of measures was assessed with intraclass correlation coefficients. RESULTS: The intra-rater and inter-rater reliability of measures was excellent (intraclass correlation coefficient > 0.85). Average cortical bone thickness measurements at the proximal humerus strongly correlated with DXA femur measurements (r = 0.64, P < .0001) and moderately correlated with DXA lumbar measurements (r = 0.49, P < .0001). Gauge cortical thickness measurements also correlated with DXA femur measurements (R = 0.53, P < .0001) and DXA lumbar measurements (R = 0.35, P < .001). An average proximal humerus cortical thickness measurement of 6 mm was identified as a potential threshold value for predicting osteoporosis, with a sensitivity of 93%, specificity of 52%, and negative predictive value of 95%. CONCLUSIONS: Average cortical bone thickness measurements obtained from standard anteroposterior shoulder radiographs are correlated with DXA. Furthermore, they provide a clinically relevant, rapid, sensitive, and inexpensive method for ruling out osteoporosis.
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