Morphometric X-ray absorptiometry and morphometric radiography of the spine: A comparison of prevalent vertebral deformity identification

Prevalent vertebral deformities are associated with a substantially increas ed risk of subsequent vertebral and nonvertebral fractures. Knowledge of ve rtebral fracture status is an important component in the prediction of furt her fractures in patients with osteoporosis. This study reports a compariso n of the quantitative identification of vertebral deformities on morphometr ic X-ray absorptiometry (MXA) scans and conventional radiographs (MRX) in 1 61 postmenopausal women (mean age +/- SD, 64 +/- 7.1 years) recruited from patients referred by their family doctor for bone density measurement (n = 119) and osteoporotic subjects with known vertebral deformities attending a n osteoporosis clinic (n = 42). Each subject Bad MXA scans and MRXs of the thoracolumbar spine, to image the vertebrae from T4-L4, at a single visit. The scans and radiographs were analyzed by two trained observers using six points to quantify the shape of each vertebral body. From these points, thr ee vertebral heights were measured: anterior, middle, and posterior. Verteb ral deformities were identified using the algorithms proposed by Eastell an d by McCloskey, Generally good to excellent agreement (per vertebra, kappa = 0.87-0.93; per subject, kappa = 0.81-0.91) was observed between the two a lgorithms used for quantitative vertebral deformity identification using MX A or MRX. More moderate agreement (per vertebra, K = 0.70-0.79; per subject , K = 0.67-0.75) was seen when comparing the same algorithm between MXA and MRX. Agreement between MXA and MRX for the McCloskey: algorithm was better than for the Eastell algorithm, largely because of the lower number of fal se positives produced by the McCloskey methodology. Deformity identificatio n by MXA was limited because of poor image quality, primarily in the upper thoracic spine. One in six MRX deformities were missed by MXA as they occur red in vertebrae not visualized sufficiently for analysis on the MXA scans. Deformity identification was poorer in the upper thoracic spine fn analyza ble vertebrae with a sensitivity of 50.0 % for MXA in terms of MRX using th e Eastell algorithm for the vertebral levels T4-T7, compared with 80.6% for L1-L4. MXA proved to be more effective at identifying moderate to severe M RX deformities producing a sensitivity of 22.0 % for MXA in Germs of identi fying MRX grade 1 deformities using the Eastell algorithm, compared with 81 .6% for grade 2 deformities. Although MXA image quality is inferior to that of conventional radiographs, MXA has distinct advantages such as a substan tially reduced effective dose to the patient and acquisition of a single im age of the spine. MXA is: a potentially useful, relatively fast, low-radiat ion technique to identify prevalent vertebral deformities, particularly mod erate to severe deformities in the middle/lower thoracic and lumbar spine, in conjunction with morphometric radiography in some patients.