Prediction of osteoporosis and osteopenia by routine computed tomography of the lumbar spine in different regions of interest

Regions of interest in opportunistic computed tomography-based screening for osteoporosis: impact on short-term in vivo precision

OBJECTIVE

To determine an optimal region of interest (ROI) for opportunistic screening of osteoporosis in terms of short-term in vivo diagnostic precision.

MATERIALS AND METHODS

We included patients who underwent two CT scans and one dual-energy X-ray absorptiometry scan within a month in 2022. Deep-learning software automatically measured the attenuation in L1 using 54 ROIs (three slice thicknesses × six shapes × three intravertebral levels). To identify factors associated with a lower attenuation difference between the two CT scans, mixed-effect model analysis was performed with ROI-level (slice thickness, shape, intravertebral levels) and patient-level (age, sex, patient diameter, change in CT machine) factors. The root-mean-square standard deviation (RMSSD) and area under the receiver-operating-characteristic curve (AUROC) were calculated.

RESULTS

In total, 73 consecutive patients (mean age ± standard deviation, 69 ± 9 years, 38 women) were included. A lower attenuation difference was observed in ROIs in images with slice thicknesses of 1 and 3 mm than that in images with a slice thickness of 5 mm (p < .001), in large elliptical ROIs (p = .007 or < .001, respectively), and in mid- or cranial-level ROIs than that in caudal-level ROIs (p < .001). No patient-level factors were significantly associated with the attenuation difference. Large, elliptical ROIs placed at the mid-level of L1 on images with 1- or 3-mm slice thicknesses yielded RMSSDs of 12.4-12.5 HU and AUROCs of 0.90.

CONCLUSION

The largest possible regions of interest drawn in the mid-level trabecular portion of the L1 vertebra on thin-slice images may yield improvements in the precision of opportunistic screening for osteoporosis via CT.

Accuracy of Phantomless Calibration of Routine Computed Tomography Scans for Opportunistic Osteoporosis Screening in the Spine Clinic

STUDY DESIGN

Diagnostic accuracy study.

OBJECTIVE

To establish a simple method of phantomless bone mineral density (BMD) measurement by using preoperative lumbar computed tomography (CT) scans, and compare the accuracy of reference tissue combinations to diagnose low BMD against uncalibrated Hounsfield units (HUs).

SUMMARY OF BACKGROUND DATA

HUs are used as a measure of BMD; however, associations between HU and T-scores vary widely. Quantitative CT (qCT) scans are more accurate, but they require density calibration with an object of known density (phantom), which limits feasibility. As an emerging technique, phantomless (internal) calibration of routine CT scans may provide a good opportunity for screening.

MATERIALS AND METHODS

Patients who were scheduled to undergo lumbar surgery, with a preoperative CT scan, and a dual-energy x-ray absorptiometry (DXA) scan within six months were included. Four tissues were selected for calibration: subcutaneous adipose (A), erector spinae (ES), psoas (P), and aortic blood (AB). The HUs of these tissues were used in linear regression against ground-truth values. Calibrations were performed by using two different internal tissues at a time to maintain simplicity and in-office applicability.Volumetric bone mineral densities (vBMD) derived from internally calibrated CT scans were analyzed for new threshold values for low bone density. Areas under the curve (AUC) were calculated with 95% CI.

RESULTS

Forty-five patients were included (M/F=10/35, mean age: 63.3). Calibrated vBMDs had stronger correlations with DXA T -scores when compared with HUs, with L2 exhibiting the highest coefficients. Calibration by using A and ES with the threshold of 162 mg/cm 3 had a sensitivity of 90% in detecting low BMD (AUC=0.671).

CONCLUSIONS

This novel method allows simple, in-office calibration of routine preoperative CT scans without the use of a phantom. Calibration using adipose and erector spinae with a threshold of 162 mg/cm 3 is proposed for low bone density screening with high sensitivity (90%).

LEVEL OF EVIDENCE

Level III.

Hounsfield units predict vertebral compression fractures in gastric cancer survivors after adjuvant irradiation

PURPOSE

This study aimed to investigate the risk factors and predictive value of vertebral Hounsfield units (HUs) for vertebral compression fracture (VCF) development in gastric cancer (GC) patients who received adjuvant radiotherapy (RT).

MATERIALS AND METHODS

We retrospectively analyzed the data of 271 patients with non-metastatic GC who received adjuvant RT between 2010 and 2020. The vertebral bodies from 9th thoracic (T9) to 2nd lumbar (L2) were contoured in computed tomographies used for RT planning, and V30, V35, V40, mean doses, and HUs of vertebrae were documented. We conducted univariate and multivariate analyses to identify the risk factors for VCF development.

RESULTS

The median follow-up time was 35.7 months. VCF developed in 23 patients (8.5%) in a median of 30.6 months (range, 3.4 to 117.3) after the end of RT. In total, 37 vertebrae were fractured, with 14 located in T12, nine in L1, seven in T11, four in L2, and three in T10. Older age, female sex, non-smoking status, and lower median vertebrae HUs were significantly associated with VCF in the univariate analysis. In the multivariate analysis, lower median HUs of T12 vertebrae (odds ratio, 0.965; 95% confidence interval, 0.942 to 0.989; p = 0.004) remained significant. The optimal cut-off value for T12 HU was 205.1, with an area under the receiver operating characteristic curve of 0.765, sensitivity of 85.7%, and specificity of 65%.

CONCLUSION

The lower median HU value of T12 vertebrae is a significant and independent risk factor for VCF development in GC patients who received adjuvant RT. HUs values serve as a simple and reliable predictor of VCF development in this population.

The Incidence of Osteoporosis in Hepatocellular Carcinoma Patients Under 65: A Retrospective Cohort Study

INTRODUCTION

Hepatocellular carcinoma (HCC) patients have a heightened prevalence of low bone mineral density (BMD) and the development of osteoporosis. Osteoporosis screening guidelines only recommend dual-energy X-ray absorptiometry (DEXA) scans for females 65 and older and males 70 and older. We set out to analyze the incidence of low BMD in HCC patients under 65 years old and encourage implementation of DEXA screenings for this patient population.

METHOD

In this retrospective cohort study, 170 patients under 65 with an HCC diagnosis were analyzed. Hounsfield units (HU) from L1 non-contrast CT scans are a reliable predictor of T-scores from DEXA scans and were used to predict BMD in patients, with scores of less than 165 HU indicative of osteopenia and less than 98 indicative of osteoporosis.

RESULTS

The median HU score of patients was 137.2, and the mean score was 142.6 (minimum: 55.4; maximum: 303.1). Of the total 170 patients, 128 (75%) had an HU score of less than 165, indicating a high likelihood of suffering from low BMD. Among low BMD patients, 25 (20%) were identified as within a range of osteoporosis.

CONCLUSIONS

HCC patients under 65 have an increased incidence of bone demineralization. We suggest that BMD in HCC patients is an important prognostic tool and parameter to document, as studies have shown that HCC patients with high BMD have longer overall survival than patients with low BMD. Future prospective studies using DEXA scans to assess BMD should be completed to verify the risk of osteoporosis.

Assessing bone quality in hounsfield units using computed tomography: what value should be used to classify bone as normal or osteoporotic?

PURPOSE

The purpose of this study was to investigate threshold values for classifying bone as normal or osteoporotic based on Computed Tomography (CT) Hounsfield Units (HU) and to determine if clinically applicable values could be derived to aid spine surgeons evaluating bone quality using CT.

METHODS

This literature review was completed using PubMed and Ovid (MedLine), using syntax specific to bone quality and CT. The included articles were original clinical studies assessing bone quality and utilized composite L1-L4 HU values compared against dual-energy X-ray absorptiometry (DEXA) values. Extracted data study descriptors, CT measurement technique, and CT threshold values. CTs were measured from L1-L4 using either axial or sagittal images, and must classify their bone quality findings for any of the following 3 categories: normal, osteopenia, or osteoporosis.

RESULTS

This review located 34 studies measuring bone density using CT with threshold values, of which, 10 were included in the final review. Number of patients ranged from 74 to 283 and cohort ages from 20s to 70.6 years. CT threshold values for assessing normal and osteoporotic bone quality ranged from 150 to 179 and 87 to 155, respectively. From combining values across studies, a HU value of ≥ 170 HU was associated with normal bone and ≤ 115 HU with osteoporosis.

CONCLUSION

There is variation in HU values used to differentiate normal from compromised bone quality, even after limiting studies. For patients with HU values between or near 170 or 115 HU, a DEXA scan may be warranted for further evaluation. With ongoing investigation in this area, threshold values for classifying bone quality using CT will be continually refined.

Preoperative Hounsfield Units Predict Pedicle Screw Loosening in Osteoporotic Patients Following Short-Segment Lumbar Fusion

STUDY DESIGN

Retrospective Cohort.

OBJECTIVE

(1) To determine if vertebral HU values obtained from preoperative CT predict postoperative outcomes following one to three level lumbar fusion and (2) to investigate whether decreased BMD values determined by HU predict cage subsidence and screw loosening.

SUMMARY OF BACKGROUND DATA

In light of suboptimal screening for osteoporosis, vertebral computerized tomography (CT) Hounsfield Units (HU), have been investigated as a surrogate for bone mineral density (BMD).

MATERIALS AND METHODS

In this retrospective study, adult patients who underwent one to three level posterior lumbar decompression and fusion (PLDF) or transforaminal lumbar interbody and fusion (TLIF) for degenerative disease between the years 2017 and 2022 were eligible for inclusion. Demographics and surgical characteristics were collected. Outcomes assessed included 90-day readmissions, 90-day complications, revisions, patient-reported outcomes (PROMs), cage subsidence, and screw loosening. Osteoporosis was defined as HU of ≤110 on preoperative CT at L1.

RESULTS

We assessed 119 patients with a mean age of 59.1, of whom 80.7% were white and 64.7% were nonsmokers. The majority underwent PLDF (63%) compared with TLIF (37%), with an average of 1.63 levels fused. Osteoporosis was diagnosed in 37.8% of the cohort with a mean HU in the osteoporotic group of 88.4 compared with 169 in nonosteoporotic patients. Although older in age, osteoporotic individuals did not exhibit increased 90-day readmissions, complications, or revisions compared with nonosteoporotic patients. A significant increase in the incidence of screw loosening was noted in the osteoporotic group with no differences observed in subsidence rates. On multivariable linear regression osteoporosis was independently associated with less improvement in visual analog scale (VAS) scores for back pain.

CONCLUSIONS

Osteoporosis predicts screw loosening and increased back pain. Clinicians should be advised of the importance of preoperative BMD optimization as part of their surgical planning and the utility of vertebral CT HU as a tool for risk stratification.

LEVEL OF EVIDENCE

3.

What can we learn about bone density in COPD patients from a chest CT? A systematic review

We systematically reviewed the current research literature to 1) investigate whether there was a difference in bone mineral density (BMD) between chronic obstructive pulmonary disease (COPD) patients and non-COPD controls, 2) determine the influence of severity and subtype of COPD on BMD, and 3) determine the risk factors for lower BMD in COPD patients. The Web of Science and PubMed databases were searched on September 25, 2023. Studies where BMD was evaluated with computed tomography (CT) or quantitative CT in patients with COPD were included in the review. We collected data on the number of COPD patients, the average age, average body mass index, average predicted forced expiratory volume in one second (%) or Global Initiative for Chronic Obstructive Lung Disease stage, the average of low attenuation areas, the use of corticosteroid therapy, the use of osteoporosis therapy, the average BMD, and the location of BMD measurement. Twelve studies met our review criteria. Although in several studies COPD was associated with a decreased BMD, most of the studies suggested that COPD, especially in its milder forms, was not strongly associated with osteopenia or osteoporosis of the thoracic and lumbar spine.

What can we learn about bone density in COPD patients from a chest CT? A systematic review

We systematically reviewed the current research literature to 1) investigate whether there was a difference in bone mineral density (BMD) between chronic obstructive pulmonary disease (COPD) patients and non-COPD controls, 2) determine the influence of severity and subtype of COPD on BMD, and 3) determine the risk factors for lower BMD in COPD patients. The Web of Science and PubMed databases were searched on September 25, 2023. Studies where BMD was evaluated with computed tomography (CT) or quantitative CT in patients with COPD were included in the review. We collected data on the number of COPD patients, the average age, average body mass index, average predicted forced expiratory volume in one second (%) or Global Initiative for Chronic Obstructive Lung Disease stage, the average of low attenuation areas, the use of corticosteroid therapy, the use of osteoporosis therapy, the average BMD, and the location of BMD measurement. Twelve studies met our review criteria. Although in several studies COPD was associated with a decreased BMD, most of the studies suggested that COPD, especially in its milder forms, was not strongly associated with osteopenia or osteoporosis of the thoracic and lumbar spine.

Risk Factors for Adjacent Vertebral Fractures Following Cement Vertebroplasty: The Clinical Significance of Multiple Preexisting Vertebral Compression Fractures

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The study retrospectively analyzed the factors associated with the development of adjacent vertebral fractures.

SUMMARY OF BACKGROUND DATA

Adjacent vertebral fractures (AVF) may occur following cement vertebroplasty, and several risk factors have been reported with controversies.

METHODS

A total of 123 patients, with a mean age of 79.2 years, who underwent single-level vertebroplasty were included in the investigation. We systematically collected data encompassing baseline demographics, osteoporosis parameters, surgical details, radiologic measurements, and Hounsfield unit (HU) values in the lumbar spine. Subsequently, univariable, followed by multivariable logistic regression analyses, were employed to identify the risk factors of AVFs.

RESULTS

Thirty of 123 patients had AVFs within 6 months following vertebroplasty. The AVF group exhibited a higher percentage of multiple preexisting vertebral compression fractures (P=0.006), a greater volume of injected cement (P=0.032), and a more pronounced reduction in local kyphosis (P=0.007). Multivariable logistic regression analysis revealed multiple preexisting vertebral compression fractures and a reduction in local kyphosis exceeding 8 degrees were independent risk factors for AVFs (P=0.008 and 0.003, respectively), with odds ratios of 3.78 (95% confidence interval: 1.41-10.12) and 4.16 (95% CI: 1.65-10.50), respectively. Subgroup analysis showed that patients with multiple preexisting vertebral compression fractures (VCFs) had significantly lower bone mineral density Z-score, T-score, and HU values compared with those without preexisting VCFs (P<0.05). Conversely, there were no significant differences in T-score or HU values between patients with no VCFs and those with a single VCF.

CONCLUSION

This study demonstrated that both bone strength and local alignment are key factors associated with adjacent vertebral fractures. Specifically, having multiple preexisting vertebral compression fractures and a reduction in local kyphosis exceeding 8 degrees are independent risk factors. The presence of more than one previous vertebral compression fracture serves as a significant clinical indicator of advanced bone density reduction in patients with osteoporosis, offering a quick and straightforward method for identifying high-risk patients. Patients exhibiting these risk factors should be monitored more closely for favorable clinical outcomes.

LEVEL OF EVIDENCE

Level III-retrospective nonexperimental study.

Using advanced imaging to measure bone density, compression fracture risk, and risk for construct failure after spine surgery

Low bone mineral density (BMD) can predispose to vertebral body compression fractures and postoperative instrumentation failure. DEXA is considered the gold standard for measurement of BMD, however it is not obtained for all spine surgery patients preoperatively. There is a growing body of evidence suggesting that more routinely acquired spine imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) can be opportunistically used to measure BMD. Here we review available studies that assess the validity of opportunistic screening with CT-derived Hounsfield Units (HU) and MRI-derived vertebral vone quality (VBQ) to measure BMD of the spine as well the utility of these measures in predicting postoperative outcomes. Additionally, we provide screening thresholds based on HU and VBQ for prediction of osteopenia/ osteoporosis and postoperative outcomes such as cage subsidence, screw loosening, proximal junctional kyphosis, and implant failure.

Side specific differences of Hounsfield-Units in the osteoporotic lumbar spine

Background

Gold standard for determining bone density as a surrogate parameter of bone quality is measurement of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA), most commonly performed on the lumbar spine (L1-L4). Computed tomography (CT) data are often available for surgical planning prior to spine procedures, but currently this information is not standardized for bone quality assessment. Besides, measuring the Hounsfield-Units (HU) is also of great importance in the context of biomechanical studies. This in vitro study aims in comparing BMD from DXA and HU based on diagnostic CT scans. In addition, methods are presented to quantify local density variations within bones.

Methods

One hundred and seventy-six vertebrae (L1-L4) from 44 body donors (age 84.0±8.7 years) were studied. DXA measurements were obtained on the complete vertebrae to determine BMD, as well as axial CT scans with a slice thickness of 1 mm. Using Mimics Innovation Suite image processing software (Materialise NV, Leuven, Belgium), two volumes (whole vertebra vs. spongious bone) were formed for each vertebra, which in turn were divided in their left and right sides. From these total of six volumes, the respective mean HU was determined. HU of the whole vertebra and just spongious HU were compared with the BMD of the corresponding vertebrae. Side specific differences were calculated as relative values.

Results

Whole bone and spongious HU correlated significantly (P>0.001; α=0.01) with BMD. A positive linear correlation was found, which was more pronounced for whole bone HU (R=0.72) than for spongious HU (R=0.62). When comparing the left and right sides within each vertebra, the HU was found to be 10% larger on average on one side compared to the opposite side. In some cases, the difference of left and right spongious bone can be up to 170%. There is a tendency for the side comparison to be larger for the spongious HU than for the whole vertebra.

Conclusions

Determination of HU from clinical CT scans is an important tool for assessing bone quality, primarily by including the cortical portion in the calculation of HU. Unlike BMD, HU can be used to distinguish precisely between individual regions. Some of the very large side-specific gradients of the HU indicate an enormous application potential for preoperative patient-specific planning.

The role of sarcopenia in fragility fractures of the pelvis - is sarcopenia an underestimated risk factor?

BACKGROUND

Fragility fractures of the pelvis (FFPs) represent a significant health burden, particularly for the elderly. The role of sarcopenia, an age-related loss of muscle mass and function, in the development and impact of these fractures is not well understood. This study aims to investigate the prevalence and impact of osteoporosis and sarcopenia in patients presenting with FFPs.

METHODS

This retrospective study evaluated 140 elderly patients with FFPs. The diagnosis of sarcopenia was assessed by psoas muscle area (PMA) and the height-adjusted psoas muscle index (PMI) measured on computed tomography (CT) scans. Clinical data, radiological findings and functional outcomes were recorded and compared with the presence or absence of sarcopenia and osteoporosis.

RESULTS

Our study cohort comprised 119 female (85.0%) and 21 (15.0%) male patients. The mean age at the time of injury or onset of symptoms was 82.26 ± 8.50 years. Sarcopenia was diagnosed in 68.6% (n = 96) patients using PMA and 68.8% (n = 88) using PMI. 73.6% (n = 103) of our study population had osteoporosis and 20.0% (n = 28) presented with osteopenia. Patients with sarcopenia and osteoporosis had longer hospital stays (p < 0.04), a higher rate of complications (p < 0.048) and functional recovery was significantly impaired, as evidenced by a greater need for assistance in daily living (p < 0.03). However, they were less likely to undergo surgery (p < 0.03) and the type of FFP differed significantly (p < 0.04). There was no significant difference in mortality rate, pre-hospital health status, age or gender.

CONCLUSION

Our study highlights the important role of sarcopenia in FFPs in terms of the serious impact on health and quality of life in elderly patients especially when osteoporosis and sarcopenia occur together. Identifying and targeting sarcopenia in older patients may be an important strategy to reduce pelvic fractures and improve recovery. Further research is needed to develop effective prevention and treatment approaches that target muscle health in the elderly.

Comparisons of Hounsfield units and volumetric bone density in discriminating vertebral fractures on lumbar CT scans

OBJECTIVES

To compare the performance of areal Hounsfield units (aHUs), volumetric Hounsfield units (vHUs), and volumetric bone mineral density (vBMD) by quantitative CT (QCT) in discriminating vertebral fractures (VFs) risk.

METHODS

We retrospectively included CT scans of the lumbar spine 101 VFs cases (60 women, mean age: 64 ± 4 years; 41 men, mean age: 73 ± 10 years) and sex- and age-matched 101 control subjects (60 women, mean age: 64 ± 4 years; 41 men, mean age: 72 ± 7 years). In order to assess the discriminatory capability of aHU, vHU, and vBMD measurements at the L1 and L2 levels in identifying VFs, we conducted binary logistic regression and receiver operating characteristic (ROC) curve analyses in men and women. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

In both men and women with and without VFs, aHU, vHU, and vBMD were highly correlated with each other (r2 from 0.832 to 0.957, all P < .001). There was a statistically significant difference in aHU, vHU, and vBMD between subjects with and without VFs (P < .001). When age, gender, and BMI were taken into account as covariances and adjusted simultaneously, odds ratios (ORs) for aHU, vHU, and vBMD values, which represent the risk of VFs, were significant (P < .001). Compared with aHU and vHU, vBMD was more strongly associated with VF risk (vBMD: OR, 6.29; 95% CI, 3.83-10.35 vs vHU: OR, 3.64; 95% CI, 2.43-5.46 vs aHU: OR, 2.56; 95% CI, 1.79-3.67). In both men and women, further, vBMD had higher values for AUC, sensitivity, specificity, PPV, and NPV compared to vHU, with vHU in turn surpassing aHU. The area under the receiver operating characteristic curve (AUC) for discriminating VFs using the average aHU, vHU, and vBMD of 2 vertebrae was 0.72, 0.77, and 0.87 in men and 0.76, 0.79, and 0.86 in women. In both men and women, there exist statistically significant differences in the AUC when employing the 3 measurements-namely, aHU, vHU, and vBMD-to discriminate fractures (P < .05).

CONCLUSIONS

The QCT-measured vBMD is more associated with acute VFs than vHU and aHU values of the lumbar spine. Although the use of vHU and aHU values for the diagnosis of osteoporosis and discriminating fracture risk is limited to scanner- and imaging protocol-specific, they have great potential for opportunistic osteoporosis screening, particularly vHU.

ADVANCES IN KNOWLEDGE

The novelty of this study presents a comparison of the VF discriminative capabilities among aHU, vHU, and vBMD. The vHU values introduced in this study demonstrate a greater capacity to discriminate fractures compared to aHU, presenting an improved clinical choice. Although its discriminatory capability is slightly lower than that of vBMD, it is more convenient to measure and does not require specialized software.