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. 2025 May;15(4):2218-2225.
doi: 10.1177/21925682241291519. Epub 2024 Oct 13.

The Association Between Hounsfield Units and Mechanical Failure in ASD Patients

Martin Heegaard  1 , Kristin Ingadottir  1 , Lærke Ragborg  1 , Benny Dahl  1 , Lars Valentin Hansen  1 , Søren Ohrt-Nissen  1 , Martin Gehrchen  1
Affiliations

The Association Between Hounsfield Units and Mechanical Failure in ASD Patients

Martin Heegaard et al. Global Spine J. 2025 May.

Abstract

Study designRetrospective Cohort Study.ObjectivesLow bone mineral density (BMD) is a known risk factor for revision surgery in patients with adult spinal deformity (ASD). Hounsfield units (HUs) on CT scans have been suggested as a proxy for assessing BMD. This study aimed to determine HUs in the lumbar region and their association with mechanical failure in patients undergoing ASD surgery.MethodsWe included ASD patients undergoing surgery from 2010-2020 with minimum 2-year follow-up. We excluded patients without preoperative CT scans, or a CT scan more than 1 year before surgery. Mechanical failure was defined as proximal junctional failure, pseudarthrosis, or implant failure requiring revision surgery. On preoperative CT scans, HUs were measured on 3 axial slices on each vertebra from L1-L5 and, if available, at UIV and UIV + 1.ResultsWe included 170 patients, mean age 63 (±12) years, with 108 (64%) females, and 13 [IQR 10-16] instrumented levels. Mechanical failure occurred in 27% (n = 46) of patients at 2-year follow-up. Mean lumbar HUs were 146 (±51) in the mechanical failure group and 135 (±52) in those without revision (P = .232). Area under the curve was 0.58 (95% CI: 0.48-0.68), corresponding to no to low discriminatory power in predicting mechanical failure using lumbar HUs. Univariate logistic regression revealed no significant difference between mechanical failure and lumbar HUs (OR = 1.00, 95% CI: 1.00-1.01, P = .239).ConclusionsWe found no association between mechanical failure and HUs on preoperative CT scans in ASD patients. Thus, we cannot recommend using HUs to predict mechanical failure in these patients.

Keywords: CT; adult spinal deformity; hounsfield units; mechanical failure; revision surgery.

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Conflict of interest statement

Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: MG: Institutional grants from Cerapedics, institutional grants from NuVasive, institutional grants from Stryker; BD: Stryker (consultancy), supported by The Alfred Benzon Foundation; the remaining authors report no conflicts of interest.

Figures

Figure 1.
Figure 1.
Illustration of Hounsfield units assessment. Hounsfield units were measured on 3 axial slices from L1 to L5 and, if available, at UIV and UIV + 1 (B–D). In cases of previous instrumented surgery, the Hounsfield units were measured on 1 axial slice either above or below the pedicle screw (A).
Figure 2.
Figure 2.
Lumbar Hounsfield units to predict mechanical failure using a receiver operating characteristics curve to determine area under the curve.
See this image and copyright information in PMC

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