Abstract
To determine the prevalence of significant left-right differences in hip bone mineral density (BMD), and the impact of this difference on osteoporosis diagnosis, we measured bilateral proximal femora using dual energy X-ray absorptiometry (DXA) in 3481 subjects (608 males, 2873 females). The difference between left and right hip was considered significant if it exceeded the smallest detectable difference (SDD) for any of the three hip subregions. Contralateral femoral BMD was highly correlated at all measuring sites (r = 0.92–0.95). However, significant left-right differences in BMD were common: the difference exceeded the SDD for 54% of patients at total hip, 52.1% at femoral neck, and 57.7% at trochanter. The prevalence of left-right differences was greater in participants >65 years. For 1169 participants with normal spines, 22 (1.9%) had discordant left-right hips in which one hip was osteoporotic; for 1349 patients with osteopenic spines, 94 (7%) had osteoporosis in one hip. Participants with BMI < 20 kg/m2 were more likely to show major T-score discordance (osteoporosis in one hip and normal BMD in the other). Multiple regression analysis showed that the only significant statically parameter that persists after adjusting for all potential confounding parameters were age over 65 years.
Highlights
Dual-energy X-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) accurately and reproducibly
The aim of our study was to measure the prevalence of significant left-right differences in hip BMD, and to determine how it impacted the classification of bone status as normal, osteopenia, or osteoporosis
(ii) Thereafter, we focused on cases, in which a diagnosis of osteoporosis would be dependent on bone status of the hip, and those cases in which one side was osteoporotic but not the contralateral side
Summary
Dual-energy X-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) accurately and reproducibly. BMD of the femoral neck is a stronger predictor of hip fractures than measurement of the spine or radius and bone experts emphasize bone mineral area density (BMD in g/cm2) measurements of the proximal femur and spine, where trabecular bone loss is accelerated and where fractures occur [4]. T-score discordance between the lumbar spine and hip testing sites is a commonly observed phenomenon in densitometry [5, 6]. T-score discordance is the observation that the T-score of an individual patient varies from one key measurement site to another. Artifacts such as osteoarthritis and osteophytic calcifications of the lumbar spine influence spine BMD measurements [7]. Liu et al [9] found that in individuals older than 60 yr of age, 75% of women and 61% of men had some evidence of osteophytes
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