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

Samuel Davidson, Alison Vecellio, Ilexa R Flagstad, Kenneth Holton, Angela S Bruzina, Paul A Lender, Susanne Trost, David Polly

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)677-683
Number of pages7
JournalSpine Deformity
Issue number3
StatePublished - May 2023

Bibliographical note

Funding Information:
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.

Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Scoliosis Research Society.


  • Bone mineral density (BMD)
  • Computed tomography (CT)
  • Dual-energy X-ray absorptiometry (DXA)

PubMed: MeSH publication types

  • Journal Article


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