Hounsfield Units (HU) derived from CT scans are a promising bone mineral density surrogate in pediatrics, yet their reliability in patients with scoliosis and significant lumbar tilt remains unknown. We investigated the reliability of HU measurements in adolescent idiopathic scoliosis (AIS), particularly addressing the impact of spinal tilt.
Methods
We retrospectively reviewed lumbar CT images of 11- to 19-year-old AIS patients who underwent posterior spinal fusion (July 2007-March 2024). HU values and lumbar tilt were measured at L1, L3, and L5. Reliability was assessed using intra-rater (N = 36), inter-rater (N = 30), and equivalence datasets (N = 62) comparing standard pelvis-parallel images versus images reconstructed parallel to the vertebral body.
Results
Both intra-rater (ICC(1,1) > 0.95) and inter-rater (ICC(2,1) > 0.80) reliability were excellent. Measurements from standard pelvis-parallel images and reconstructed images showed stable overall equivalence (ICC(3,1) = 0.96). However, the percentage of cases with an HU value difference of 20 or more was 11.3% when the lumbar tilt angle was 10 degrees or greater, compared to 5.6% when the tilt angle was below 9 degrees.
Conclusion
Our analyses for AIS patients showed that vertebral HU measurements are reliable when using vertebral-parallel reconstructed images but standard pelvis-parallel images lose reliability with significant tilt. While our findings do not promote routine CT usage, our validated methodology provides a baseline technique that could potentially be applied to complex, high-risk cases where osteoporosis is prevalent and critical for surgical planning.
BACKGROUND
Osteoporotic vertebral compression fractures (OVCFs) are prevalent but frequently remain unrecognized. While bone mineral density (BMD) is the primary assessment tool, MRI-based parameters associated with bone and muscle quality may offer additional value, yet sex-specific analyses are limited, despite sex differences in incidence and hormones.
PURPOSE
To explore the associations between MRI-based vertebral bone quality (VBQ) score, psoas muscle index (PMI), and paravertebral muscle fat infiltration (FI) fraction with OVCFs, and to assess the potential diagnostic performance of MRI parameters across sexes.
STUDY TYPE
Retrospective.
POPULATION
260 subjects (≥ 50 years); 130 OVCF patients (73.0 years (67.0-80.0), 89 females) and 130 non-fracture (NF) patients (64.5 years (58.0-73.0), 76 females).
FIELD STRENGTH AND SEQUENCES
3 T and 1.5 T. T1-weighted TSE and T2-weighted TSE (Siemens) and T1-weighted FSE and T2-weighted FSE (United Imaging).
ASSESSMENT
VBQ was calculated on sagittal T1-weighted MRI; PMI and FI were quantified on axial T2-weighted MRI at the L3 endplate by ImageJ. BMD was derived from CT using QCT PRO software. Two trained observers, blinded to clinical data, performed all MRI measurements.
STATISTICAL TESTS
Significance level was set at p < 0.05. t-test/Mann-Whitney U test, chi-squared test (χ2), Spearman's rank correlation coefficient, multivariate logistic regression, receiver operating characteristic (ROC) curve analysis with area under the curve (AUC). Bootstrap resampling (1000 iterations) for internal validation.
RESULTS
The OVCF group exhibited significantly elevated VBQ (3.71 ± 0.55 vs. 3.25 ± 0.58) and FI (24.11% (21.66-28.92) vs. 20.31% (18.90-22.14)), while PMI (3.42 ± 1.02 vs. 4.08 ± 1.14) and BMD (55.82 mg/cm3 (38.75-70.90) vs. 89.24 mg/cm3 (67.80-110.00)) were reduced. FI was independently associated with OVCFs exclusively in females (OR = 1.566). The combined MRI model (VBQ + FI + PMI) yielded a significantly higher AUC in females (AUC = 0.896) than in males (AUC = 0.720).
DATA CONCLUSION
VBQ, PMI, and FI reveal significant sex-specific correlations with OVCFs. The multi-parametric MRI model shows considerable potential as a diagnostic aid for OVCFs in individuals aged over 50, particularly in females.
LEVEL OF EVIDENCE: 4
TECHNICAL EFFICACY STAGE
2 (Diagnostic Accuracy).
Meng Sun, Wanling Jiang, Haoyu Wang et al.· Journal of Magnetic Resonanc...· 1 citation
OBJECTIVE
This study aimed to compare the efficacy of endplate Hounsfield unit (HU) values and endplate bone quality (EBQ) scores in predicting cage subsidence (CS) after posterior lumbar interbody fusion (PLIF) in older patients and identify the most discriminative bone mineral density (BMD) assessment indicator.
METHODS
This retrospective analysis included consecutive patients who underwent PLIF at the authors' institution between January 2016 and February 2024. Clinical data were collected for all patients. Propensity scores were used to match patients with and without CS, and the matched cohort was subjected to conditional logistic regression to investigate the association between radiographic factors and CS. L1 and endplate HU values were derived from CT scans, whereas vertebral bone quality (VBQ) and EBQ scores were derived from MR images. Receiver operating characteristic curve analysis was conducted to assess the predictive value of endplate HU values and EBQ scores for CS and further compare their predictive value with that of L1 HU values and VBQ scores.
RESULTS
This study included 130 matched patients. The CS group demonstrated lower L1 (p < 0.001) and endplate HU (p < 0.001) values and higher VBQ (p = 0.002) and EBQ (p < 0.001) scores compared with the non-CS group. The conditional logistic regression analysis identified L1 HU value (OR 0.99, 95% CI 0.97-0.99; p = 0.036), endplate HU value (OR 0.99, 95% CI 0.98-0.99; p = 0.044), VBQ score (OR 2.40, 95% CI 1.34-4.32; p = 0.038), and EBQ score (OR 4.46, 95% CI 2.16-9.18; p = 0.003) as independent predictors of CS, demonstrating areas under the curve of 0.722, 0.815, 0.648, and 0.782, respectively. The optimal cutoff for the endplate HU value in predicting CS was 262.11 (sensitivity 83.08%, specificity 73.85%).
CONCLUSIONS
Endplate HU values indicated a relatively higher predictive performance for CS compared with EBQ scores and served as the most discriminative BMD indicator in patients who underwent PLIF. Measuring the endplate HU value preoperatively helps surgeons select a more appropriate surgical plan and is expected to improve patient outcomes.
Peng Du, Minghui Liang, Ruiyuan Chen et al.· Journal of Neurosurgery : Sp...· 0 citations
RATIONALE AND OBJECTIVES
Evaluating and Comparing the Predictive Ability of computed tomography (CT)-based Hounsfield units (HU), Magnetic resonance imaging (MRI)-based vertebral bone quality score (VBQ) and modified VBQ scores for pedicle screw loosening (PSL) in patients with lumbar degenerative diseases.
MATERIALS AND METHODS
Retrospective study of patients undergoing transforaminal lumbar interbody fusion (TLIF) for degenerative diseases (Dec 2019 - Jan 2021). Screw loosening was assessed using 12-month postoperative lumbar radiographs and defined by a ≥1 mm radiolucent halo surrounding the screw. Various VBQ scores and HU value were measured using preoperative MRI and CT, respectively. Predictive performance was evaluated using receiver operating characteristic (ROC) curve analysis.
RESULTS
Among all patients (n = 185), several modified VBQ scores showed higher areas under the curve (AUCs) than the VBQ score (0.776, 95% CI: 0.701-0.851) and CT HU value (0.770, 95% CI: 0.684-0.857), without statistical significance (PAUC>0.05). No significant differences were observed in lumbar disc herniation (LDH) or spondylolisthesis (LS) subgroups. In lumbar spinal stenosis (LSS) patients, the AUC of T1-VBQFAT (0.876, 95% CI: 0.788-0.965) was significantly higher than that of CT HU value (0.718, 95% CI: 0.583-0.852) (PAUC=0.040).
CONCLUSION
In the overall cohort and other subgroups, HU values and several modified VBQ scores showed numerically higher AUCs without statistical significance (PAUC>0.05). In the LSS subgroup, T1-VBQFAT demonstrated superior predictive performance compared with HU values (PAUC=0.040); notably, this finding did not remain statistically significant after correction for multiple comparisons (PAUC>0.0026). These exploratory results suggest that T1-VBQFAT may serve as a potential adjunct for predicting PSL in patients with LSS.
Haoxiang Yang, Yichao Mao, Wu Ye et al.· Academic Radiology· 0 citations
Pedicle screw loosening is a common and clinically significant complication of instrumented lumbar fusion and is reported in 15%-30% of screws in osteoporotic patients. Dual-energy X-ray absorptiometry (DEXA)-based bone mineral density (BMD) has long served as the standard preoperative assessment tool; however, its well-recognized limitations in the degenerative spine and its modest correlations with fixation strength have prompted growing interest in computed tomography (CT)-derived bone quality metrics as complementary alternatives. This study aims to synthesize the current evidence based on CT-derived Hounsfield unit (HU) measurements as preoperative predictors of pedicle screw insertional torque and postoperative screw loosening in degenerative lumbar fusion surgery, with a specific focus on trajectory-specific techniques. A narrative review of studies indexed in PubMed and MEDLINE (1990-2026) was conducted using the following search terms: 'Hounsfield units pedicle screw,' 'CT bone quality lumbar fusion,' 'screw loosening BMD,' 'trajectory HU insertional torque,' and 'vertebral bone quality score.' Studies were included if they reported quantitative bone quality metrics in adult patients undergoing lumbar instrumented fusion with outcomes of insertional torque or radiographic screw loosening. Non-human or cadaveric-only studies were excluded unless they were directly relevant to clinical threshold derivation. Multiple retrospective studies consistently demonstrated that trajectory-specific HU, measured within a cylindrical or single-slice region of interest matched to the planned screw trajectory, outperformed lumbar and femoral DEXA in correlating with insertional torque (r=0.75 vs. r=0.55-0.59) and predicting 12-month screw loosening. Three-dimensional trajectory HU and single-slice measurements both showed clinical utility, with proposed exploratory thresholds of 110-123 HU, although these values were derived from single-center, heterogeneous CT acquisition protocols and were not validated across institutions. The magnetic resonance imaging-based Vertebral Bone Quality score demonstrated comparable performance to vertebral body HU for overall loosening prediction, although trajectory-specific comparisons have not yet been published. The evidence supports an emerging framework for transitioning from systemic DEXA-based BMD to localized, trajectoryspecific CT-HU assessment as a complementary tool for preoperative pedicle screw planning. Prospective validation, standardization of measurement protocols, cross-scanner calibration, and integration into surgical navigation platforms are the critical next steps before clinical translation can be recommended.
S. Dhar, R. Dar, Tarsem Lal Motten et al.· Asian Spine Journal· 0 citations
To compare lumbar vertebral trabecular attenuation using CT-based Hounsfield unit (HU) measurements among patients with adrenal incidentalomas (AIs) with mild autonomous cortisol secretion (MACS), non-functioning adrenal incidentalomas (NFAIs), and controls. This retrospective study included 507 patients with AIs who underwent non-contrast abdominal CT. The study sample comprised 121 patients divided into NFAI [cortisol ≤ 1.8 µg/dL following dexamethasone suppression test (DST); n = 76] and MACS (cortisol > 1.8 µg/dL following DST; n = 45) groups. The control group consisted of 48 age- and gender-matched patients. Two radiologists independently measured trabecular HU values in L1–L5 vertebrae. Predictors of low bone mineral density (BMD) (L1 HU < 110) were evaluated using multivariate analyses. A total of 169 patients (mean age, 59 years ± 10 [SD], 50 men) were evaluated. No significant differences existed between groups in age or gender. Mean L1 and L2 HU values were significantly lower in the MACS group (L1: p = 0.027; L2: p = 0.014). Inter-observer reliability was excellent (ICC: 0.932–0.982). A strong correlation was observed between mean L1 HU and lumbar DXA T-score (r = 0.895; p < 0.001). Multivariate analysis identified age, parathyroid hormone level, and patient group as independent predictors of L1 HU < 110. Low BMD risk was significantly lower in the NFAI group (OR = 0.232; p = 0.009). MACS was associated with low trabecular bone attenuation in the upper lumbar vertebrae. Opportunistic CT screening may contribute to bone health risk stratification in AI patients without additional radiation exposure.
Ahmet Faruk Gürbüz, Süleyman Uluçay, Cemal Kaştan et al.· Bratislava Medical Journal· 0 citations
OBJECTIVE
This study compared Hounsfield unit (HU) measurements obtained from different regions of interest (ROIs) on lumbar CT for assessing bone mineral density (BMD) and discriminating osteoporosis and thoracolumbar fragility fracture status, aiming to evaluate whether ROI selection meaningfully influences HU-based assessment.
METHODS
Five HU measurement methods were evaluated using lumbar CT. Their correlations with dual-energy X-ray absorptiometry (DEXA)-derived BMD and their discriminative performance for osteoporosis and thoracolumbar fragility fracture status were analyzed. Receiver operating characteristic (ROC) curves were constructed, and pairwise comparisons of areas under the curve (AUCs) were performed using the DeLong test. A sensitivity analysis was additionally conducted after excluding substituted vertebral levels and recalculating mean lumbar HU using only non-substituted vertebrae.
RESULTS
All five HU measurement methods showed significant correlations with DEXA-derived BMD, and no statistically significant differences in discriminative performance were observed among the five ROI methods in the primary analysis. In the sensitivity analysis excluding substituted vertebral levels, the AUCs remained comparable across methods for osteoporosis (0.816-0.826) and thoracolumbar fragility fracture status (0.677-0.689), with all pairwise DeLong tests showing no statistically significant differences (all p > 0.05).
CONCLUSION
Different lumbar CT ROI methods demonstrated comparable performance in assessing BMD and discriminating thoracolumbar fragility fracture status, and sensitivity analysis confirmed that exclusion of substituted vertebral levels did not materially affect the results. No ROI method showed statistically significant superiority, suggesting that ROI selection may be guided by clinical feasibility and workflow convenience rather than by diagnostic performance alone.
ADVANCES IN KNOWLEDGE
This study compares five commonly used lumbar CT HU measurement methods and shows that their performance is broadly similar. The findings suggest that ROI selection may be guided primarily by clinical feasibility and workflow convenience, although further external validation is required before routine clinical application.
