Identification of vertebral deformities in women: comparison of radiological assessment and quantitative morphometry using morphometric radiography and morphometric X-ray absorptiometry.

Abstract

Our aim was to compare normal vertebral reference values for morphometric radiography (MRX) and morphometric X-ray absorptiometry (MXA) and to compare these methods for the identification of vertebral deformities. We calculated MXA reference values (Hologic QDR 4500 A) for 327 women (ages 22-88 years) randomly selected from local General Practice lists in Sheffield, U.K. MRX reference values were calculated from spinal radiographs for 123 of these subjects (ages 56-88 years). We used these reference values to identify deformities in the MRX and MXA reference populations and in 83 women with osteoporosis (ages 49-87 years). We observed differences in mean deformity of vertebral height ratios measured by MRX and MXA, especially for the mid-to-posterior ratio. We compared agreement between quantitative methods (MRX and MXA) and qualitative radiological assessment. Severity of deformity was defined by semiquantitative (SQ) assessment. Agreement was moderate for MRX (k = 0.59; 95% CI = 0.43-0.77) and for MXA (k = 0.47; 95% CI = 0.29-0.66) in the reference population. Agreement was good for MRX (k = 0.86; 95% CI = 0.82-0.89) and MXA (k = 0.71; 95% CI = 0.66-0.75) in the osteoporotic population. MRX and MXA correctly identified a greater proportion of moderate or severe deformities compared with mild deformities. Sensitivity, specificity, predictive values, and accuracy were slightly better for MRX than for MXA. Although MXA agrees well with qualitative radiological assessment, the large proportion of vertebrae excluded from analysis because of poor image quality limits the diagnostic value of the technique. Reference intervals should be technique specific.