Abstract
Prevalent vertebral fractures indicate a high risk of subsequent fractures, which makes fracture identification play a key role in the management of osteoporosis. Dual-energy X-ray absorptiometry can provide images for assessment of vertebral morphometry (MXA) with a much lower radiaton dose than conventional radiography, but it is still uncertain wether the resolution of MXA is adequate for vertebral morphometry. The aim of the study was to compare the number and level of agreement of quantitative morphometry of the vertebrae on lateral views of the spine using conventional X-ray (MRX) and using a dual X-ray absorbtiometry device (DXA/MXA)) in determining if there is a fracture of the vertebrae, and the degree of fracture in patients with osteoporosis. In order to test for concordance between spine fracture identification on conventional lateral X-ray and lateral X-rays obtained from DXA scans we investigated 74 patients with osteoporosis, who underwent DXA to acquire single-energy morphometric X-ray absorptiometry (MXA) scans and conventional lateral radiography (MRX) of the thoracic and lumbar spine. Adequate images were obtained in 99,2 % of the 1258 vertebrae by MRX and 77,7 % by MXA when vertebrae T1 to L5 were counted. Poor image quality was mostly found at T1-T4 and L4-L5 by MXA, and incident fractures of vertebra T5 were excluded from analysis because of poor image quality due to overlap of the ilium. Vertebral anterior and posterior heights were measured and the anterior/posterior (AP)-ratio was calculated. MRX and MXA showed concordant results with respect to presence of fracture in 94,9 % of vertebrae examined. Concordance with respect to fracture severity (SQ grade) was 94,1 %. MXA graded 21 vertebrae (2,2 %) to be one SQ level higher than corresponding vertebrae on MRX images, while only 15 vertebrae (1,6 %) were graded as one SQ level higher using MRX. This represents a difference of 6 vertebrae (0,6 %). 7 vertebrae (0,7 %) were graded to be two SQ levels higher in MXA images than for MRX images, while this is the case in 4 vertebrae (0,4 %) in MRX images compared to MXA. This represents a difference of 3 vertebrae (0,3 %). Both MRX and MXA measurement graded one vertebrae (0,1 %) to be three fracture degrees higher. In conclusion we have demonstrated acceptable concordance between conventional X-ray readings and readings obtained from lateral X-rays from DXA scanners. Both techniques agreed on the presence of fractures in 95 % of cases and on fracture severity in 94 % of cases. This makes MXA well suited for assessment of spine fracture status in routine clinical practice. As the presence of spine fractures are major determinants of future fracture risk, but clinically silent in 80 % of cases the routine use of MXA should be expanded.