Visual identification of vertebral fractures in osteoporosis using morphometric X-ray absorptiometry

Abstract

Visual identification of vertebral fractures from spinal radiographs (visual XR) makes use of the reader's expertise in ruling out non-fracture deformities or normal variants. Scan images of the spine acquired by DXA may be analyzed quantitatively (morphometric X-ray absorptiometry [quantitative MXA]) or visually (visual MXA). The aims of this study were to compare visual and quantitative MXA with visual XR for the identification of vertebral fractures. Spinal radiographs and MXA scans were acquired at baseline and 1 year in 70 women referred with osteoporosis. These were assessed visually by two expert readers (observer A, a radiologist; observer B, a physician with expertise in osteoporosis) for evidence of prevalent and incident vertebral fractures. Observer C (a radiographer with expertise in vertebral morphometry) performed visual and quantitative assessments of the MXA scans. Visual assessment of spinal radiographs by observer A was used as the gold standard for comparison of methods. Sensitivity for the identification of prevalent fractures by MXA was best for visual MXA by observer A (92%), whereas quantitative MXA had the lowest sensitivity (82%). Specificity was >90% for both visual and quantitative MXA. Kappa scores for agreement for identification of prevalent fractures between visual XR (observer A) and visual MXA (all three observers), and between visual XR and visual MXA performed by reader B were similar (kappa = 0.85-0.87). Agreement with visual XR performed by observer A was slightly lower for quantitative MXA (kappa = 0.77). Interobserver agreement between the two expert readers (observers A and B) was the same for both visual XR and visual MXA (kappa = 0.86). Seven incident vertebral fractures were identified in four patients at follow-up. All four patients were identified by visual MXA, and three patients were identified by quantitative MXA. Observers A and B identified all seven incident fractures by visual MXA, and observer C missed one fracture that was also missed by quantitative MXA. An incident fracture of vertebra T6 was excluded from analysis by quantitative MXA because of poor image quality. We conclude that visual identification of vertebral fractures from MXA scans is superior to quantitative assessment. Used as a screening tool for conventional radiography, this approach could help reduce the radiation dose to the patient in the diagnosis and monitoring of osteoporosis.