A patient in his late adolescence was referred for evaluation of low and apparently declining spinal bone density on dual-energy X-ray absorptiometry (DXA). Review of the DXA images revealed normal bone mineral density at other body sites but exceedingly low lumbar spine Z-scores which appeared to get progressively lower over time. The DXA result was explained by congenital spinal dysraphism with absent posterior spinous elements, rather than true low bone mineral content. Recognition of this structural artefact prevented unnecessary interventions. The case underscores the importance of correlating DXA scan results with clinical context and anatomic variations of bone structure, and of direct image review by the interpreting clinician. Understanding the technical principles and limitations of DXA, including artefact recognition, is essential to avoid misdiagnosis.
Wang et al. (Mon,) studied this question.