Vertebral Body Hounsfield Units Research Articles

680 Lower Preoperative Hounsfield Units Predict Distal Junctional Kyphosis After Posterior Cervical Decompression and Fusion

INTRODUCTION: Low bone mineral density (BMD) may predispose patients to structural and adjacent segment complications after spine surgery. While dual energy X-ray absorptiometry (DEXA) remains the gold standard for BMD quantification, it is rarely performed on a routine basis prior to cervical fusion. Alternatively, vertebral body Hounsfield Units (HU) may provide useful and convenient estimates on BMD. However, minimal evidence exists to evaluate the value of HU in predicting postoperative complications after cervical fusion. METHODS: A retrospective, single-institution analysis was conducted, focusing on patients who underwent PCDF without a history of cervical spine surgery. Preoperative vertebral body HU were measured at each level of the cervical spine, and demographic, clinical, and postoperative complication data were recorded. RESULTS: 166 patients were eligible for inclusion (mean age 66 ± 12 years), with an average follow-up time of 13.5 months. In a multivariate logistic regression analysis, controlling for age, gender, and construct length, lower HU at the superior instrumented level were associated with increased rates of distal junctional kyphosis (p = 0.042, AUC = 0.86). Additionally, lower HU at the superior adjacent level were associated with increased rates of revision surgery (p = 0.016, AUC > 0.99). CONCLUSIONS: Preoperative cervical HU offer valuable insight in anticipating structural complications after PCDF, and HU may be useful for identifying patients who require preoperative BMD optimization.

Inter-Rater Reliability and Correlation of L1 Hounsfield Unit Measurements with DXA Scores

Introduction: While prior studies have generally reported rigorous protocols using prespecified CT scanner settings for HU measurements, the present study sought to report on the correlation between DXA and HUs recorded using several CT scanners with varying sequences, simulating measurements performed in “real-world” hospital and Emergency Department (ED) settings. Methodology: Six raters performed HU measurements of trabecular bone at the L1 vertebral body for forty consecutive patients on Phillips and General Electric (GE) abdominal CT scans obtained between 2017 and 2021. Inter-rater reliability of the HU measurements and their correlations with recorded DXA-based bone assessments were determined. Correlation coefficients were calculated for the HU measurements between scanner vendors as well as for the CT HUs with each DXA measurement. Results: The ICC for L1 HUs read on the Phillips and GE scanners were 0.85 and 0.82, respectively, indicating excellent agreement. The correlation coefficient for the mean HUs on the Phillips and GE scanners was 0.92, also indicating excellent correlation. For both scanner vendors, the HU values most closely correlated with the total femur and femoral neck T-scores. Conclusions: HU values recorded on a Phillips and GE scanner both demonstrated excellent inter-rater reliability. Correlations were strongest between L1 HU values and total femur DXA T-scores. Readily available abdominal CT image data across multiple hospital settings can be utilized by providers of varying level of imaging interpretation expertise to determine vertebral body Hounsfield units that may help identify osteoporosis risk without additional radiation exposure or cost.

Assessment of vertebral bone mineral density and stand-alone oblique lumbar interbody fusion for adjacent segment disease and primary lumbar degenerative diseases.

To evaluate the vertebral bone mineral density and the value of stand-alone oblique lumbar interbody fusion (SA OLIF) for the management of single-level adjacent segment disease (ASD) and primary lumbar degenerative diseases. Seventy-eight patients undergoing single-level SA OLIF was divided into index surgery group (n = 36) or revision surgery group (n = 42) at single center. The vertebral body Hounsfield units (HU) value was measured to assess bone mineral density of operated level by the preoperative CT. The following data were retrospectively collected and compared between the two groups: demographic, surgical data, clinical results, and complications. No differences were found between the two groups in surgical data. The fusion segment HU values in the revision group were significantly higher than that in the index group (147.4 ± 35.3 vs 129.2 ± 38.4 p = .033). There were significant differences while comparing fusion segment HU values to L1-L4 horizontal plane (147.4 ± 35.3 vs 126.1 ± 28.4, p = .000) and L1 (147.4 ± 35.3 vs 126.8 ± 26.2, p = .000) in revision group, meanwhile, no statistically significant difference was observed in index group (p > .05). The cage subsidence was observed in the revision group (n = 2) and index group (n = 9) (p = .045). The patients with cage subsidence had significantly lower vertebral HU values. SA OLIF is valid alternative to the traditional posterior approach in the management of ASD with good clinical outcomes at short-term follow-up. Increased HU values of fusion segment may play a role in the management of ASD by SA OLIF.

Radiomic Modeling of Bone Density and Rib Fracture Risk After Stereotactic Body Radiation Therapy for Early-Stage Non-Small Cell Lung Cancer

PurposeOur purpose was to determine whether bone density and bone-derived radiomic metrics in combination with dosimetric variables could improve risk stratification of rib fractures after stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). Methods and MaterialsA retrospective analysis was conducted of patients with early-stage NSCLC treated with SBRT. Dosimetric data and rib radiomic data extracted using PyRadiomics were used for the analysis. A subset of patients had bone density scans that were used to create a predicted bone density score for all patients. A 10-fold cross validated approach with 10 resamples was used to find the top univariate logistic models and elastic net regression models that predicted for rib fracture. ResultsA total of 192 treatment plans were included in the study with a rib fracture rate of 16.1%. A predicted bone density score was created from a multivariate model with vertebral body Hounsfield units and patient weight, with an R-squared of 0.518 compared with patient dual-energy x-ray absorptiometry T-scores. When analyzing all patients, a low predicted bone density score approached significance for increased risk of rib fracture (P = .07). On competing risk analysis, when stratifying patients based on chest wall V30 Gy and bone density score, those with a V30 Gy ≥30 cc and a low bone density score had a significantly higher risk of rib fracture compared with all other patients (P < .001), with a predicted 2-year risk of rib fracture of 28.6% (95% confidence interval, 17.2%-41.1%) and 4.9% (95% confidence interval, 2.3%-9.0%), respectively. Dosimetric variables were the primary drivers of fracture risk. A multivariate elastic net regression model including all dosimetric variables was the best predictor of rib fracture (area under the curve [AUC], 0.864). Bone density variables (AUC, 0.618) and radiomic variables (AUC, 0.617) have better predictive power than clinical variables that exclude bone density (AUC, 0.538). ConclusionRadiomic features, including a bone density score that includes vertebral body Hounsfield units and radiomic signatures from the ribs, can be used to stratify risk of rib fracture after SBRT for NSCLC.

P117. Bone density distribution in the cervical spine: Establishing level specific reference values

<h3>BACKGROUND CONTEXT</h3> Bone density in the lumbar spine is variable by level and can impact surgical strategy. In the cervical spine, low Hounsfield units (HU) have been associated with cage subsidence. The distribution of HU in the cervical spine has not been established. <h3>PURPOSE</h3> To define level-specific cervical HU reference values and the relationship between cervical bone density, age, BMI, comorbidities and alignment. <h3>STUDY DESIGN/SETTING</h3> Retrospective review at a single center from May 2015 to December 2019. <h3>PATIENT SAMPLE</h3> A total of 224 patients, 18 excluded for previous hardware and 5 for known osteoporosis. <h3>OUTCOME MEASURES</h3> Hounsfield units. <h3>METHODS</h3> Patients who presented with neck symptoms and had a cervical spine CT for evaluation of pathology or surgical planning were included. Exclusions were hardware on CT, osteoporosis, or cervical deformity. Measurements were performed in 5 regions of each vertebral body (VB) (C2-T1; mid-axial, anterior-axial, posterior-axial, mid-coronal, and mid-sagittal) and 2 regions of the lateral masses (LMs) (C3-C6; mid-cor, mid-sag). The VB measurements were averaged at each level to obtain a composite value of each vertebral body (TotalVB), similarly the mid-cor and mid-sag values were averaged at each LM (TotalLatM). Outliers were excluded pairwise. To evaluate reliability, 6 observers each measured 355 HU values (71 over 5 patients), inter-relater reliability assessed with intraclass correlation coefficients (ICCs). Correlations of composite HU with age, BMI, Charlston Comorbidity Index (CCI) and cervical alignment were evaluated. <h3>RESULTS</h3> Average age 57±12 years, mean BMI 28±6 kg/m2, 63.5% male, 90.1% white. Diagnoses included radiculopathy (45.8%), myelopathy (37.9%) and facet arthropathy (46.3%). ICC for HU measurements were as follows: VB, 0.82 mid-axial, 0.59 ant-axial, 0.77 post-axial, 0.88 mid-cor, 0.88 mid-sag; LM, 0.46 mid-sag, 0.61 mid-cor. C4 VB and C4 LM had the highest HU (383.6±71.9 and 480.0±103, respectively) while T1 VB and C6 LM had the lowest (232.3±46.5 and 398.3±98.2, respectively). No significant correlations were found between LM HU and age, BMI, CCI, or alignment. Increased kyphosis was weakly correlated with VB HU at all levels (except C2) strongest correlations at C7 (0.25) and weakest correlation at C3 (0.16). Age and CCI showed weak-moderate correlations with VB HU at all levels (age, r=-0.20 to -0.35; CCI r=-0.28 [C2, C7, T1] to -0.17 [C4]). <h3>CONCLUSIONS</h3> Our level-specific cervical HU values may be referenced when evaluating cervical BMD. The most reliable measurement technique is on the mid-sag or mid-cor VB, measurement of LMs is less reliable. Bone is least dense in the lower cervical spine, which may influence instrumentation strategies. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

265. Lumbar vertebral body Hounsfield units are associated with cage subsidence after transforaminal lumbar interbody fusion

BACKGROUND CONTEXT Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) interbody cages can result in loss of lordosis and foraminal height, and in some cases recurrence of nerve root impingement and radicular symptoms. Hounsfield unit (HU) values as measured on computed tomography (CT) can be used in the assessment of bone quality and bone mineral density. PURPOSE Determine the association between HU measurement of the first lumbar vertebral body and cage subsidence after TLIF. We hypothesized that the HU measured in the vertebral body of L1 would be lower in patients with postoperative TLIF cage subsidence. STUDY DESIGN/SETTING Retrospective case-control study. PATIENT SAMPLE NA OUTCOME MEASURES NA METHODS We retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. Postoperative imaging studies (radiographs and CT) were evaluated for evidence of implant subsidence. Hounsfield unit values were obtained from the first lumbar vertebral body on postoperative CT scan. Primary outcomes of this study were presence of cage subsidence and measured HU value of first lumbar vertebral body. RESULTS We identified 89 patients with complete imaging who met our inclusion criteria, with a mean clinical follow up of 27 months. Forty-five patients (50.5%) had evidence of interbody cage subsidence. Average cage subsidence was 5.5mm, with a range of 2.2 to 10.8mm. We found implant height was significantly higher in the subsidence group (12.6mm) when compared to the nonsubsidence group (11.2mm). First lumbar vertebral body coronal (170.69±15.61 vs 138.64±14.21; P=0.003), sagittal (175.14±17.26 vs 140.16±13.71; P=0.002), axial (157.57±12.26 vs 134.35±12.30.83; P=0.009), and average HU (167.8±14.04 vs 137.71±12.83; P=0.002) were significantly higher in the non-subsided group vs subsided group (167.8±14.04 vs 137.71±12.83; P=0.002). The subsidence group had a fusion rate of 82% compared to 93% in the nonsubsidence group, although this finding did not reach statistical significance (p=0.08). CONCLUSIONS We found that HU measurements of the first lumbar vertebra are significantly higher in patients without evidence of TLIF cage subsidence when compared to patients with cage subsidence. We identified a trend toward a decreased fusion rate in the subsidence group, yet this finding was not statistically significant. Our findings suggest that HU measurements may function as a surrogate measurement for bone mineral density, and as a predictor for cage subsidence following TLIF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Lumbar disc height and vertebral Hounsfield units: association with interbody cage subsidence.

Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) cages can result in loss of lordosis and foraminal height, and potential recurrence of nerve root impingement. The objectives of this study were to determine factors associated with TLIF cage subsidence. Specifically, the authors sought to determine if preoperative disc height compared to cage height could be used to predict TLIF interbody cage subsidence, and if decreased postoperative vertebral Hounsfield units (HUs) predisposed to cage subsidence. The authors retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. The preoperative disc height was measured for the operative and adjacent-level disc on MRI. The difference between cage and disc heights was measured and compared between the subsidence and nonsubsidence groups. The average HUs of the L1 vertebral body were measured on CT scans. Eighty-nine patients were identified with complete imaging and follow-up information. Forty-five patients (50.6%) had evidence of interbody cage subsidence on follow-up CT. The average cage subsidence was 5.5 mm (range 2.2-10.8 mm). The average implant height was significantly higher in the subsidence group compared to the nonsubsidence group (12.6 vs 11.2 mm). Additionally, the difference between cage height and preoperative adjacent-level disc height was also significantly larger in the subsidence group (3.8 vs 1.2 mm). First lumbar vertebral body (L1) HUs were significantly higher in the nonsubsidence versus the subsidence group (167.8 vs 137.71 HUs, p = 0.002). Multivariate logistic regression analysis identified suprajacent disc height and L1 HUs to be independent predictors of interbody cage subsidence. Receiver operating characteristic curves identified a suprajacent to cage height difference > 1.3 mm to have a 93.3% sensitivity for cage subsidence. This study is the first of its kind to demonstrate the association between vertebral body HUs and suprajacent disc height with the development of interbody cage subsidence after TLIF. The authors found that patients with lower HUs in the L1 vertebral body were more likely to experience subsidence, regardless of surgical level. Additionally, the study demonstrated that interbody cage height > 1.3 mm above the height of the suprajacent level is an independent risk factor for cage subsidence, with 93.3% sensitivity. These findings suggest that these factors may be utilized to create a template preoperatively for intraoperative cage selection.

Hounsfield units of the vertebral body and pedicle as predictors of pedicle screw loosening after degenerative lumbar spine surgery.

The authors aimed to compare the efficacy of lumbar vertebral body Hounsfield units (HUs) and pedicle HUs at predicting pedicle screw loosening. The authors retrospectively assessed 143 patients with L3-5 instrumentation. The patients were classified into one of two groups based on the status of their L3 screws (a screw loosening group or a control group). The pedicle HUs and vertebral HUs of L3 were measured using preoperative lumbar CT scans, and the pedicle HUs were measured in two ways: by excluding or by including cortical bone. The screw loosening rate was 20.3% (n = 29/143) at the 12-month follow-up. The vertebral body HUs and pedicle HUs in the screw loosening group were lower than those in the control group (vertebral body group: 98.6 HUs vs 121.4 HUs, p < 0.001; pedicle excluding cortical bone: 208.9 HUs vs 290.5 HUs, p = 0.002; pedicle including cortical bone: 249.4 HUs vs 337.5 HUs, p < 0.001). The pedicle HUs tended to have a higher area under the receiver operating characteristic curve value in predicting screw loosening, compared with that of vertebral body HUs, but the difference was not statistically significant (p > 0.05). Among patients with low vertebral body HUs of ≤ 130, the loosening rate was much lower in patients with pedicle HUs of ≤ 340 than in those with pedicle HUs of > 340 (31.0% vs 13.0%, respectively; p < 0.05). Vertebral body HUs alone are insufficient to accurately evaluate the risk of pedicle screw loosening. Therefore, it is important to collect both the pedicle HU and vertebral body HU measurements for surgical planning.

Osteoporotic Fracture Risk and Vertebral Body Hounsfield Units as Predictors of Stereotactic Body Radiotherapy Induced Rib Fracture

Osteoporotic Fracture Risk and Vertebral Body Hounsfield Units as Predictors of Stereotactic Body Radiotherapy Induced Rib Fracture

Machine Learning Model to Predict Osteoporotic Spine with Hounsfield Units on Lumbar Computed Tomography.

ObjectiveBone mineral density (BMD) is an important consideration during fusion surgery. Although dual X-ray absorptiometry is considered as the gold standard for assessing BMD, quantitative computed tomography (QCT) provides more accurate data in spine osteoporosis. However, QCT has the disadvantage of additional radiation hazard and cost. The present study was to demonstrate the utility of artificial intelligence and machine learning algorithm for assessing osteoporosis using Hounsfield units (HU) of preoperative lumbar CT coupling with data of QCT. MethodsWe reviewed 70 patients undergoing both QCT and conventional lumbar CT for spine surgery. The T-scores of 198 lumbar vertebra was assessed in QCT and the HU of vertebral body at the same level were measured in conventional CT by the picture archiving and communication system (PACS) system. A multiple regression algorithm was applied to predict the T-score using three independent variables (age, sex, and HU of vertebral body on conventional CT) coupling with T-score of QCT. Next, a logistic regression algorithm was applied to predict osteoporotic or non-osteoporotic vertebra. The Tensor flow and Python were used as the machine learning tools. The Tensor flow user interface developed in our institute was used for easy code generation. ResultsThe predictive model with multiple regression algorithm estimated similar T-scores with data of QCT. HU demonstrates the similar results as QCT without the discordance in only one non-osteoporotic vertebra that indicated osteoporosis. From the training set, the predictive model classified the lumbar vertebra into two groups (osteoporotic vs. non-osteoporotic spine) with 88.0% accuracy. In a test set of 40 vertebrae, classification accuracy was 92.5% when the learning rate was 0.0001 (precision, 0.939; recall, 0.969; F1 score, 0.954; area under the curve, 0.900). ConclusionThis study is a simple machine learning model applicable in the spine research field. The machine learning model can predict the T-score and osteoporotic vertebrae solely by measuring the HU of conventional CT, and this would help spine surgeons not to under-estimate the osteoporotic spine preoperatively. If applied to a bigger data set, we believe the predictive accuracy of our model will further increase. We propose that machine learning is an important modality of the medical research field.

Assessment of Osteoporosis in Injured Older Women Admitted to a Safety-Net Level One Trauma Center: A Unique Opportunity to Fulfill an Unmet Need.

Background Older trauma patients often undergo computed tomography (CT) as part of the initial work-up. CT imaging can also be used opportunistically to measure bone density and assess osteoporosis. Methods In this retrospective cohort study, osteoporosis was ascertained from admission CT scans in women aged ≥65 admitted to the ICU for traumatic injury during a 3-year period at a single, safety-net, level 1 trauma center. Osteoporosis was defined by established CT-based criteria of average L1 vertebral body Hounsfield units <110. Evidence of diagnosis and/or treatment of osteoporosis was the primary outcome. Results The study cohort consisted of 215 women over a 3-year study period, of which 101 (47%) had evidence of osteoporosis by CT scan criteria. There were no differences in injury severity score, hospital length of stay, cost, or discharge disposition between groups with and without evidence of osteoporosis. Only 55 (59%) of the 94 patients with osteoporosis who survived to discharge had a documented osteoporosis diagnosis and/or corresponding evaluation/treatment plan. Conclusion Nearly half of older women admitted with traumatic injuries had underlying osteoporosis, but 41% had neither clinical recognition of this finding nor a treatment plan for osteoporosis. Admission for traumatic injury is an opportunity to assess osteoporosis, initiate appropriate intervention, and coordinate follow-up care. Trauma and acute care teams should consider assessment of osteoporosis in women who undergo CT imaging and provide a bridge to outpatient services.

Vertebral Body Hounsfield Units as a Predictor of Incidental Durotomy in Primary Lumbar Spinal Surgery

Retrospective cohort study. To assess the association between vertebral body Hounsfield unit (HU) measurements on quantitative computed tomography and the risk for incidental durotomy (ID). ID during spine surgery has been associated with adverse postoperative sequelae that may require prolonged hospital stay and reoperation. Previously identified independent risk factors include age, revision surgery, and lumbar surgery. ID was prospectively documented in spine surgery patients at a single institution during a 2-year period (incidence: 4%, 191/4,822). Patients with ID were matched 1:1 to a control cohort without ID based on age and sex. Inclusion criteria for both cohorts were primary lumbar surgery and quantitative computed tomographic scans within 1 year of date of surgery. Demographic, radiographical, and intraoperative data, along with dual x-ray absorptiometry t scores, were collected and analyzed. A total of 71 patients with ID met the inclusion criteria (38 male, 33 female). Average age of patients with ID was 63.8 ± 12.9 years (range: 34-85 yr). Computed tomographic scans were acquired 1.5 ± 2.2 months away from date of surgery (range: 0-12 mo). Inter-rater reliability for HU measurements between a fellowship-trained spine surgeon and a research fellow was strong (r = 0.901, P < 0.001). HU values were significantly lower in patients with ID than controls (149.2 ± 60.7 [range: 44.5-301.5] versus 177.0 ± 81.4, [range: 62.0-524.0], respectively; P = 0.023). The area under the receiver operating characteristic curve was 0.603 (P = 0.034). A threshold of 169 HU optimized sensitivity (0.718) and specificity (0.451), and patients with HU value 169 or less were found to be at increased risk for ID (odds ratio: 2.092, 95% confidence interval: 1.042-4.201, P = 0.037). Lower HU value is an accessible clinical marker for increased risk of ID. A threshold value of HU was defined (≤169) that may be used clinically to identify patients at elevated risk for ID, which may improve the informed decision making process prior to spinal surgery. 3.