Italian preliminary reference data of normal vertebral dimensions for morphometric X-ray absorptiometry (MXA): Normal morphometric dexa (NORMODEXA) study

Accurate identification of vertebral fractures both for epidemiological studies and clinical practice depends on comparison to dimensions among normal (non fractured) vertebrae. Aim of this multicentric study is to defining Italian reference values of normal vertebral dimensions for morphometric X-ray absorptiometry. Design of the study: according to Black method¹, we included both women with and without vertebral fractures. Assuming that values of heights ratios of no fractured vertebrae follows a Gaussian distribution and that almost all the values of fractured vertebrae are in the tail of the distribution, we trimmed the highest and lowest 10% of the values. Each centre recruited a sample of women within eight 5-years age bands: fertile women <44 aged and postmenopausal women aged 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, >74 years. The centers as far as here (up till now) participating in the study were six across Italy (Ancona, Catania (2), Imola, Roma, Verona ) involving a total of 1000 women. All women enrolled had MXA of vertebrae T4-L4, two centers using the Hologic QDR4500A four centers using the GE Lunar Prodigy. Both systems acquired spine images with dual-energy (high-definition). MXA images were sent to Rome for centralized analysis by an experienced radiologist (D.D.). Results. Intra-operator precision was found to be similar on the two systems, Hologic and GE Lunar: the coefficient of variation (CV%) was 1.7% for the posterior height and 2.2% for the anterior height, resulting relatively higher in the whole upper thoracic. The age stratificated mean and standard deviation of the three vertebral heights and their ratios for all vertebral levels were calculated for both systems. No statistically significant relationship was found between vertebral heights and age in premenopausal women. Whereas, in postmenopausal women, was observed a significant inverse relationship with age (r=0.6, p<0.001) between age and mean vertebral heights and their ratios, that showed the major decrement for anterior height at T6-T8 level. Vertebral heights significantly correlated with years since menopause (r=0.5, p<0.001) decreasing much more in the first 5 years after the menopause. Conclusions: these preliminary results indicates the usefulness also for MXA of normal values stratified for age and for years since menopause. ¹ DM Black et al. A new approach to defining normal vertebral dimensions. JBMR 1991;6:883-892.