Navel Jewelry Artifacts and Intravertebral Variation in Spine Bone Densitometry in Adolescents and Young Women

Non-removable navel jewelry can increase the measured bone density of the underlying vertebra. We measured lumbar spine bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) in an observational study of 727 adolescents and young women aged 14–30yr. We evaluated several methods of correcting BMD: manually erasing a small area, eliminating 1 or 2 vertebrae, estimating the BMD from 1 or 2 vertebrae using data from remaining vertebrae, and estimating the BMD using T-scores of the remaining vertebrae. Ten percent (n=71) of the subjects were wearing navel jewelry. The areal BMD by DXA of L1 and L2 was similar in those with jewels as in controls without jewels, but L3–L4 showed higher bone density in those with jewelry, and the spine BMD of L1–L4 was significantly higher in the bejeweled women (1.043±0.011 vs 1.006±0.004g/cm2, p=0.01). The estimated errors in accuracy (g/cm2) were 0.034 due to the jewels; 0.005 from erasing a small area; 0.019 from eliminating L4; 0.044 from eliminating both L3 and L4; 0.016 from predicting BMD using L1–L3; and 0.028 using L1–L2. The T-scores using the Hologic database were progressively lower in the caudal vertebrae, even in 96 local women aged 30–35yr, whose average T-score was 0.35 at L1 but −0.26 at L4. Thus, we found significant errors due to intravertebral variability. We suggest the optimal method of correcting for small artifacts is to erase the area under the artifact.