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Discrepancy between DXA and CT-based assessment of spine bone mineral density

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Abstract

Purpose

Adequate bone mineral density (BMD) is necessary for success in spine surgery. Dual-energy X-ray absorptiometry (DXA) is the gold standard in determining BMD but may give spuriously high values. Hounsfield units (HU) from computed tomography (CT) may provide a more accurate depiction of the focal BMD encountered during spine surgery. Our objective is to determine the discrepancy rate between DXA and CT BMD determinations and how often DXA overestimates BMD compared to CT.

Methods

We retrospectively reviewed 93 patients with both DXA and CT within 6 months. DXA lumbar spine and overall T scores were classified as osteoporotic (T Score  ≤ − 2.5) or non-osteoporotic (T Score > −2.5). L1 vertebral body HU were classified as osteoporotic or non-osteoporotic using cutoff thresholds of either ≤ 135 HU or ≤ 110 HU. Corresponding DXA and HU classifications were compared to determine disagreement and overestimation rates.

Results

Using lumbar T scores, the CT vs DXA disagreement rate was 40–54% depending on the HU threshold. DXA overestimated BMD 97–100% of the time compared to CT. Using overall DXA T scores, the disagreement rate was 33–47% with DXA greater than CT 74–87% of the time. In the sub-cohort of 10 patients with very low HU (HU < 80), DXA overestimated BMD compared to CT in every instance.

Conclusions

There is a large discrepancy between DXA and CT BMD determinations. DXA frequently overestimates regional BMD encountered during spine surgery compared with CT. While DXA remains the gold standard in determining BMD, CT may play an important role in defining the focal BMD pertinent to spine surgery.

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Data availability

Data sharing is unavailable for this dataset as the research data is confidential.

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Funding

The authors did not receive support from any organization for the submitted work.

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Authors and Affiliations

  1. The Department of Orthopedic Surgery, University of Minnesota, 2512 South 7th Street, Suite R200, Minneapolis, MN, 55455, USA

    Samuel Davidson, Alison Vecellio, Ilexa Flagstad, Kenneth Holton, Angela Bruzina, Paul Lender & David Polly Jr

  2. The Department of Medicine, University of Minnesota, 2512 South 7th Street, Suite R200, Minneapolis, MN, 55455, USA

    Susanne Trost

  3. The Department of Neurosurgery, University of Minnesota, 2512 South 7th Street, Suite R200, Minneapolis, MN, 55455, USA

    David Polly Jr

Authors
  1. Samuel Davidson
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  2. Alison Vecellio
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Contributions

SD: Made substantial contributions to the conception and design of the work, and the acquisition, analysis, and interpretation of data. Drafted the work and revised it critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AV: Made substantial contributions to the acquisition, analysis, and interpretation of data. Drafted the work and revised it critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. IF: Made substantial contributions to the conception and design of the work, and the acquisition, analysis, and interpretation of data. Drafted the work and revised it critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. KH: Made substantial contributions to the conception and design of the work, and the acquisition, analysis, and interpretation of data. Revised the work critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AB: Made substantial contributions to the analysis and interpretation of data. Revised the work critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. PL: Made substantial contributions to the analysis and interpretation of data. Revised the work critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. ST: Made substantial contributions to the conception and design of the work, and the acquisition, analysis, and interpretation of data. Revised the work critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. DP Jr.: Made substantial contributions to the conception and design of the work, and the acquisition, analysis, and interpretation of data. Revised the work critically for important intellectual content. Approved the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Corresponding author

Correspondence to Samuel Davidson.

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Conflict of interest

SD, AV, IF, KH, AB, PL, and ST declare no financial conflicts. DP declares consulting fees from Globus Medical; institutional grant/research support from Medtronic and MizuhoOSI; consulting fees, royalties, and honoraria from SI-BONE, Inc; and royalties/other financial or material support from Springer. No authors disclose financial or non-financial interests directly or indirectly related to the work submitted.

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Institutional review board (IRB) approval for this project was obtained from the University of Minnesota IRB.

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Davidson, S., Vecellio, A., Flagstad, I. et al. Discrepancy between DXA and CT-based assessment of spine bone mineral density. Spine Deform 11, 677–683 (2023). https://doi.org/10.1007/s43390-023-00646-5

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