The use of clinical CT for baseline bone density assessment

Automated Opportunistic Trabecular Volumetric Bone Mineral Density Extraction Outperforms Manual Measurements for the Prediction of Vertebral Fractures in Routine CT

Opportunistic osteoporosis screening using multidetector CT-scans (MDCT) and convolutional neural network (CNN)-derived segmentations of the spine to generate volumetric bone mineral density (vBMD) bears the potential to improve incidental osteoporotic vertebral fracture (VF) prediction. However, the performance compared to the established manual opportunistic vBMD measures remains unclear. Hence, we investigated patients with a routine MDCT of the spine who had developed a new osteoporotic incidental VF and frequency matched to patients without incidental VFs as assessed on follow-up MDCT images after 1.5 years. Automated vBMD was generated using CNN-generated segmentation masks and asynchronous calibration. Additionally, manual vBMD was sampled by two radiologists. Automated vBMD measurements in patients with incidental VFs at 1.5-years follow-up (n = 53) were significantly lower compared to patients without incidental VFs (n = 104) (83.6 ± 29.4 mg/cm³ vs. 102.1 ± 27.7 mg/cm³, p < 0.001). This comparison was not significant for manually assessed vBMD (99.2 ± 37.6 mg/cm³ vs. 107.9 ± 33.9 mg/cm³, p = 0.30). When adjusting for age and sex, both automated and manual vBMD measurements were significantly associated with incidental VFs at 1.5-year follow-up, however, the associations were stronger for automated measurements (β = -0.32; 95% confidence interval (CI): -20.10, 4.35; p < 0.001) compared to manual measurements (β = -0.15; 95% CI: -11.16, 5.16; p < 0.03). In conclusion, automated opportunistic measurements are feasible and can be useful for bone mineral density assessment in clinical routine.

A radiological study of the natural history of diffuse idiopathic skeletal hyperostosis (DISH): a story of incomplete fusion

Introduction: DISH is an ankylosing disease, when fractured can be challenging to manage. A retrospective radiological study was conducted to evaluate the natural history and radiological characteristics of DISH on Computed tomography (CT).Methods: Paired CT scans with DISH that are separated at least two years apart were used to perform the following radiological measurements: Degree of disc space fusion, Osteophyte and vertebral body linear attenuation coefficients (LAC), and Osteophyte axial area size and location.Results: 164 patients were analysed with a mean duration of 4.49 years between scans. 38.14% (442/1159) of disc spaces had at least partial calcification. Most osteophytes were right sided before becoming more circumferential over time. The average fusion score was 54.17. Most of the changes in fusion occurred in the upper and lower thoracic regions. The thoracic region when compared to the lumbar region had a greater proportion of its disc spaced being fully fused. Disc level osteophyte areas were larger than Body level osteophytes. Disc osteophytes size growth rate drops over time from 10.89mm²/year in Stage 1 to 3.56mm²/year in Stage 3. Stage 3 disc spaces (-11.01HU/year) was also found to have had a reduction in their LAC over time when compared to Stage 1 disc spaces (17.04HU/year). This change in osteophyte LAC was not mirrored in the change in vertebral body LAC. We predict that the age of onset and complete thoracolumbar ankylosis of DISH to be 17.96 years and 100.59 years, respectively.Conclusion: DISH ankylosis of the spine a slow process that starts in the mid to lower thoracic region before extending cranially and caudally. After the bridging osteophyte has fully formed, remodelling of the osteophyte occurs.

The effect of contrast media on CT measures of bone mineral density: a systematic review

OBJECTIVE

The aim was to systematically assess the literature on possible effect of administration of iodinated contrast media on CT-estimated bone mineral density (BMD).

MATERIALS AND METHODS

The Web of Science and PubMed databases were searched. Studies that used both CT principles of BMD measurement (volumetric quantitative BMD and CT attenuation in Hounsfield Units) were included. The baseline patient data, skeletal site, contrast medium data (if reported), and change in BMD on contrast-enhanced CT scans were collected.

RESULTS

Sixteen studies met our review criteria, the majority of which was performed on lumbar spine, and the others on proximal femur. Almost all studies reported a significant increase in BMD values on the contrast-enhanced CT scans, ranging from 0.8 to 30.3%. The increase was most frequently reported to be about 10 to 15% for the spine and 5 to 10% for the femur. In addition to the difference in skeletal site, some authors found the contrast effect was age-, sex-, and contrast dose-dependent. BMD values in arterial phase were generally somewhat lower than in venous phase, and the effect of contrast in venous phase was more predictable.

CONCLUSION

The review revealed significant changes in BMD values between unenhanced and contrast-enhanced CT. The change was more pronounced in lumbar spine than in proximal femur and appeared to depend on age, sex, contrast dose, and postcontrast imaging protocol. The review suggests the understanding of all mentioned factors during the interpretation of BMD measured on contrast-enhanced CT.

Identification of Bone Mineral Density Deficit Using L1 Trabecular Attenuation by Opportunistic Multidetector CT Scan in Adult Patients

BACKGROUND

Multidetector computer tomography (CT) has been used to diagnose pathologies such as osteoporosis via opportunistic screening, where the assessment of the bone structure and the measurement of bone mineral density (BMD) are of great relevance.

PURPOSE

To construct reference BMD values based on the measurement of the attenuation of the L1 vertebral body by multidetector CT scan (in the soft tissue and bone windows) in adult patients and to establish normative ranges by sex and age of BMD values.

MATERIALS AND METHODS

A retrospective cross-sectional study of 5080 patients who underwent multidetector CT scan between January and December 2021. Adult patients (≥18 years) with non-contrast multidetector CT scan of the abdomen or thorax-abdomen at a voltage 120 kV. The attenuation of the L1 vertebral body in Hounsfield units (HU) in both windows were compared using the Mann-Whitney U-test with α = 0.05. Additionally, the quartiles of the BMD were constructed (in both windows) grouped by sex and age.

RESULTS

Only 454 (51.30 ± 15.89 years, 243 women) patients met the inclusion criteria. There is no difference in BMD values between windows (soft tissue: 163.90 ± 57.13, bone: 161.86 ± 55.80, p = 0.625), mean L1 attenuation decreased linearly with age at a rate of 2 HU per year, and the presence of BMD deficit among patients was high; 152 of 454 (33.48%) patients presented BMD values suggestive of osteoporosis, and of these, approximately half 70 of 454 (15.42%) corresponded to patients with BMD values suggestive of a high risk of osteoporotic fracture.

CONCLUSIONS

From clinical practice, the bone mineral density (BMD) of a patient in either window below the first quartile for age- and sex-matched peers suggests a deficit in BMD that cannot be ignored and requires clinical management that enables identification of the etiology, its evolution, and the consequences of this alteration.

Osteoporosis as a Risk Factor for Intraoperative Complications and Long-term Instrumentation Failure in Patients With Scoliotic Spinal Deformity

STUDY DESIGN

A retrospective review study.

OBJECTIVE

This study aims to determine the effect of osteoporosis on spine instrumentation.

SUMMARY OF BACKGROUND DATA

Osteoporosis is a common skeletal pathology that affects systemic cortical bone maintenance and remodeling. This disease accelerates the degeneration of the spine, often necessitating spinal surgery for progressive vertebral deformity, pathologic fracture, bony canal stenosis, and/or neural element decompression. There is a paucity of literature describing the role of osteoporosis as it relates to both perioperative complications and outcomes after spine fusion surgery.

MATERIALS AND METHODS

A retrospective review was conducted of a prospectively maintained database for patients undergoing spine surgery between January 1, 2006 and October 3, 2017. Inclusion criteria included age 18 years and above and surgery performed for the correction of thoracolumbar scoliosis. Data collected included various demographic, clinical, and operative variables.

RESULTS

A total of 532 patients met inclusion criteria, including 144 (27%) patients with a diagnosis of osteoporosis. Osteoporosis was significantly associated with increased blood volume loss (P=0.003). Postoperatively, osteoporosis was associated with increased rates of instrumentation failure (19% vs. 10%; P=0.008) and the need for revision surgery (33% vs. 16%; P<0.001). Multivariate analysis confirmed osteoporosis to be an independent risk factor for increased mean number of spinal segments fused (P<0.05), mean blood volume loss (P<0.05), rate of postoperative deep venous thrombosis/pulmonary embolism (P<0.05), rate of instrumentation failure (P<0.05), and need for revision surgery (P<0.05).

CONCLUSION

Osteoporosis is a significant risk factor for instrumentation failure and need for revision surgery following arthrodesis for scoliosis correction. Furthermore, patients with osteoporosis have a significantly higher risk of intraoperative blood volume loss and postoperative thromboembolic events.

Imaging of the Osteoporotic Spine - Quantitative Approaches in Diagnostics and for the Prediction of the Individual Fracture Risk

Osteoporosis is a highly prevalent systemic skeletal disease that is characterized by low bone mass and microarchitectural bone deterioration. It predisposes to fragility fractures that can occur at various sites of the skeleton, but vertebral fractures (VFs) have been shown to be particularly common. Prevention strategies and timely intervention depend on reliable diagnosis and prediction of the individual fracture risk, and dual-energy X-ray absorptiometry (DXA) has been the reference standard for decades. Yet, DXA has its inherent limitations, and other techniques have shown potential as viable add-on or even stand-alone options. Specifically, three-dimensional (3 D) imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), are playing an increasing role. For CT, recent advances in medical image analysis now allow automatic vertebral segmentation and value extraction from single vertebral bodies using a deep-learning-based architecture that can be implemented in clinical practice. Regarding MRI, a variety of methods have been developed over recent years, including magnetic resonance spectroscopy (MRS) and chemical shift encoding-based water-fat MRI (CSE-MRI) that enable the extraction of a vertebral body's proton density fat fraction (PDFF) as a promising surrogate biomarker of bone health. Yet, imaging data from CT or MRI may be more efficiently used when combined with advanced analysis techniques such as texture analysis (TA; to provide spatially resolved assessments of vertebral body composition) or finite element analysis (FEA; to provide estimates of bone strength) to further improve fracture prediction. However, distinct and experimentally validated diagnostic criteria for osteoporosis based on CT- and MRI-derived measures have not yet been achieved, limiting broad transfer to clinical practice for these novel approaches. KEY POINTS::   · DXA is the reference standard for diagnosis and fracture prediction in osteoporosis, but it has important limitations.. · CT- and MRI-based methods are increasingly used as (opportunistic) approaches.. · For CT, particularly deep-learning-based automatic vertebral segmentation and value extraction seem promising.. · For MRI, multiple techniques including spectroscopy and chemical shift imaging are available to extract fat fractions.. · Texture and finite element analyses can provide additional measures for vertebral body composition and bone strength.. CITATION FORMAT: · Sollmann N, Kirschke JS, Kronthaler S et al. Imaging of the Osteoporotic Spine - Quantitative Approaches in Diagnostics and for the Prediction of the Individual Fracture Risk. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1770-4626.

Fractures around the hip: inducing life-like fractures as a basis for enhanced surgical training

INTRODUCTION

In this study we investigated if realistic fracture patterns around the hip can be produced on human cadaveric specimens with intact soft tissue envelope. Possible applications of such fractured specimens would be in surgical training.

MATERIALS AND METHODS

7 cadaveric specimens (2 male, 5 female, 2 formalin-fixed, 5 fresh-frozen) were fractured. 2 specimens were fractured on both femurs, 5 only on one side, resulting in 9 fractures total. 5 fractures were set in our custom-made drop-test bench, 2 fractures by inducing axial force using a hammer, and the remaining 2 fractures by a direct dorsal approach and a chisel. AO/OTA and Pauwels classification were used to classify the fractures on the specimens by two independent trauma surgeons.

RESULTS

In our drop-test bench, axial load with the femur adducted by 10° resulted in an intertrochanteric fracture (AO type A1.3), adducted by 20° resulted in a femoral neck fracture (Pauwels type III). Fracture induction using a hammer resulted in two intertrochanteric fractures (AO type A2.2 right, A3.3 left). The use of a chisel resulted in both cases in a femoral neck fracture. The acetabulum could be fractured multifragmentarily through use of a hemiprosthesis as a stamp.

CONCLUSION

A high energetic impulse induced by a custom-made drop-test bench can successfully simulate realistic proximal femur and acetabular fractures in cadaveric specimens with intact soft tissue. Furthermore, axial load using a hammer as well as using a chisel through a direct dorsal approach represent additional methods for fracture induction. These pre-fractured specimens can be utilized in surgical education to provide a realistic teaching experience for specialized trauma education courses.

Low volumetric bone density is a risk factor for early complications after spine fusion surgery

This study aims to investigate lumbar spine (LS) volumetric bone density (vBMD) as a risk factor for complications (pseudoarthrosis, instrumentation failure, adjacent fractures), re-operation, and time to complication after fusion.

INTRODUCTION

Lumbar spine (LS) fusion surgery is increasingly performed worldwide. Complications after fusion result in significant morbidity and healthcare costs. Multiple factors, including osteoporosis, have been suggested to contribute to risk of complications and re-operation. However, most studies have used DXA, which is subject to artifact in patients with spine pathology, and none have investigated the relationship between BMD and timing of post-operative complications. This study aims to investigate LS volumetric bone density (vBMD) as a risk factor for complications (pseudoarthrosis, instrumentation failure, adjacent fractures), re-operation, and time to complication after fusion.

METHODS

We evaluated a cohort of 359 patients who had initial LS fusion surgery at our institution, had pre-operative LS CTs and post-operative imaging available for review. Demographic factors, smoking status, vBMD, and details of surgical procedure were related to likelihood and timing of post-operative complications.

RESULTS

Mean age was 60 ± 14 years, vBMD 122 ± 37 g/cm³. Median follow-up was 11 months. Skeletal complications occurred in 47 patients (13%); 34 patients (10%) required re-operation. Low vBMD (directly measured and estimated using HU) and smoking were associated with increased risk of skeletal complications. Each increase in baseline vBMD of 10 g/cm³ decreased the complication hazard and increased the complication-free duration in time-to-event analysis (hazard ratio 0.91, 95% CI 0.83-0.98, p < 0.02).

CONCLUSIONS

Low vBMD was a significant risk factor for early post-operative complications in patients undergoing LS fusion. Prospective studies are needed to confirm these findings and to elucidate the optimal timing for follow-up and strategies for prevention of post-operative complications in this population.

Bone Density at the Entry Point Correlates With the Trabecular Bone of the Thoracolumbar Vertebral Bodies - Quantitative Computed Tomography Study

PURPOSE

To evaluate the relationship between cortical Bone Mineral Density (BMD) at pedicle entry points with trabecular BMD of the vertebral body in a spinal fracture.

METHODS

Quantitative computed tomography of the thoracolumbar spine was analyzed using dedicated software - QCT Pro (Mindways, Austin, TX).

RESULTS

Forty-six patients were evaluated. Among them 36 females were diagnosed with osteoporosis; the remaining 10 randomly selected from the database both males and females served as a control group. Overall measurements for 138 vertebrae were assessed. Cortical BMD of entry points for transpedicular screws was higher than trabecular vertebral BMD in osteoporotic (p < 0.001) and non-osteoporotic patients (p = 0.003). The difference was 3.6 times higher in low BMD cases (osteoporosis), compared to 2.3 times in normal subjects. Spearman's rank correlation coefficient showed the strongest correlation between patient's age and trabecular bone mineral density of L1 vertebral body (r = -0.94, p < 0.05), while cortical entry points were less correlated (r = -0.8, p < 0.05 and r = -0.65, p < 0.05 for left and right entry points, respectively). The strength of the correlations between BMD and age decreased gradually from L1 to L4, from r = -0.94 to r = -0.58 for the trabecular vertebral body; from r = -0.8 to r = -0.37 for entry points. Significant correlations were not found for BMD and the height or weight of the patients.

CONCLUSIONS

Cortical BMD at pedicle entry points decreases with osteoporosis. The relative contribution of cortical vs trabecular BMD increases with osteoporosis. Vertebral trabecular BMD is highly correlated with the cortical BMD of the entry points and allows predicting the bone support in fracture cases.

Lower Spine Volumetric Bone Density in Patients With a History of Epidural Steroid Injections

CONTEXT

Epidural steroid injections (ESIs) are a common, effective treatment of lumbar radiculopathy and sciatica. Although the negative skeletal effects of oral glucocorticoids are well established, little is known about the impact of ESI on bone quality.

OBJECTIVE

To investigate the relationship between ESI exposure and volumetric bone mineral density (vBMD) at the lumbar spine (LS) using central quantitative CT.

DESIGN

Retrospective study.

SETTING

University hospital outpatient facility.

PATIENTS

All patients had CT scans of the LS between 2011 and 2016. Cases received at least three ESIs prior to the date of CT (n = 121). Controls were matched for age and sex (n = 121).

MAIN OUTCOME MEASURES

Cumulative ESI dose was calculated. vBMD was measured at T12 through L5 using QCT Pro phantomless software (MindWays).

RESULTS

Mean age of subjects was 65 ± 14 years, and 49% were women. Median number of ESIs was 4 (range: 3 to 16). Median cumulative ESI dosage was 340 mg of triamcinolone or equivalent (range: 150 to 1400 mg). Compared with controls, ESI subjects had lower vBMD at each vertebral level. Higher cumulative dose was associated with lower mean vBMD at T12 to L5 (r = -0.22, P = 0.02).

CONCLUSIONS

Greater cumulative ESI dose was related to lower vBMD at the LS. To our knowledge, this is the first study to measure vBMD in patients treated with ESIs. Prospective studies are needed to confirm these findings and to help identify the best strategies for preventing bone loss in this population.

Osteoporosis, obesity, and sarcopenia on abdominal CT: a review of epidemiology, diagnostic criteria, and management strategies for the reporting radiologist

Abdominal computed tomography (CT) is a widely performed examination, with many indications. Assessment of bone, fat, and muscle on abdominal CT can be performed in a quantitative manner. Published studies have developed diagnostic cutoffs for osteoporosis, obesity, and sarcopenia, which are summarized with pictorial examples. The epidemiological and prognostic significance of these disease states are outlined. Further diagnostic steps and treatment strategies are outlined to inform both the managing clinician and reporting radiologist. This article summarizes an unglamorous yet information-rich field, which is ripe for assessment in the dawning era of personalized medicine, and one in which the radiologist is well placed to add value to patient care.

The use of routine non density calibrated clinical computed tomography data as a potentially useful screening tool for identifying patients with osteoporosis

OBJECTIVES

To evaluate whether lumbar vertebral body density CT attenuation values measured in Hounsfield Units (HUs) on routine Computed Tomography (CT) examinations can be reliably measured with limited variability, and to evaluate for a correlation between HUs and bone mineral density as measured by dual energy X-ray absorptiometry (DXA) scan.

METHODS

Retrospective review of a total of 249 routine MDCT examinations, performed to measure HUs at the first non-rib bearing lumbar vertebral body on axial images, cross-referenced to the lateral scout image.

RESULTS

The overall ICC and RC for intra-reader variability on CT HU were 0.987 (95% CI 0.973 - 0.999) and 15.664 (95% CI 11.66-16.97). The overall ICC and RDC for inter-reader variability on CT HU were 0.952 (95% CI 0.892 - 0.999) and 30.20 (95% CI 23.73 - 34.48). The ICC and RC for interscanner variability were 0.98 (95% CI 0.95 - 0.99) and 16.67 (95% CI 13.13 - 22.85). The correlation between the L1 HUs and L1 BMD, L1 t-score, and overall t-score was 0.437, 0.392, and 0.400, respectively.

CONCLUSIONS

CT attenuation values of the first lumbar vertebra can be measured on routine abdomen CTs with limited variability despite multiple readers and scanners. Correlation between HU and BMD as measured by DXA scan was only weakly positive, and by this method measuring the density of a lumbar vertebral body from a routine MDCT scan does not provide the sensitivity or specificity necessary for a screening test. However above a certain measured value (180 HU), patients have a low chance of osteoporosis and therefore may not need additional screening, potentially limiting radiation exposure and cost.

Effect of IV contrast on lumbar trabecular attenuation at routine abdominal CT: correlation with DXA and implications for opportunistic osteoporosis screening

Osteoporosis remains under-diagnosed. Routine abdominal CT can provide opportunistic screening, but the effect of IV contrast is largely unknown. The overall performance for predicting osteoporosis was similar between enhanced and unenhanced scans. Therefore, both non-contrast and contrast-enhanced abdominal CT scans can be employed for opportunistic osteoporosis screening.

INTRODUCTION

Osteoporosis is an important yet under-diagnosed public health concern. Lumbar attenuation measurement at routine abdominal CT can provide a simple opportunistic initial screen, but the effect of IV contrast has not been fully evaluated.

METHODS

Mean trabecular CT attenuation values (in Hounsfield units, HU) at the L1 vertebral level were measured by oval region-of-interest (ROI) on both the unenhanced and IV-contrast-enhanced CT series in 157 adults (mean age, 62.0). All patients underwent correlative central DXA within 6 months of CT. Based on DXA BMD of the lumbar spine, femoral neck, and total proximal femur: osteoporosis, osteopenia, and normal BMD was present in 33, 77, and 47, respectively. Statistical analysis included Bland-Altman plots and receiver operating characteristic (ROC) curves.

RESULTS

Mean difference (±SD) in L1 trabecular attenuation between enhanced and unenhanced CT series was +11.2 HU (±19.2) (95 % CI, 8.16-14.22 HU), an 8 % difference. Intra-patient variation was substantial, but no overall trend in the HU difference was seen according to underlying BMD. ROC area under the curve (AUC) for unenhanced and enhanced CT for diagnosing osteoporosis were similar at 0.818 and 0.830, respectively (p = 0.632). Thresholds for maintaining 90 % specificity for osteoporosis were 90 HU for unenhanced and 102 HU for enhanced CT. Thresholds for maintaining 90 % sensitivity for osteoporosis were 139 HU for unenhanced and 144 HU for enhanced CT. Similar diagnostic performance was seen for diagnosing low BMD (osteoporosis or osteopenia) using higher HU cut-offs.

CONCLUSION

Contrast-enhanced CT shows an average increase of 11 HU over the unenhanced series for L1 trabecular attenuation. The overall performance for predicting osteoporosis is similar between the enhanced and unenhanced scans, thus either can be employed for initial opportunistic screening.

Quantitative computed tomography and opportunistic bone density screening by dual use of computed tomography scans

Central dual-energy X-ray absorptiometry (DXA) of the lumbar spine and proximal femur is the preferred method for bone mineral density (BMD) testing. Despite the fracture risk statistics, osteoporosis testing with DXA remains underused. However, BMD can also be assessed with quantitative computed tomography (QCT) that may be available when access to DXA is restricted. For patients undergoing a primary CT study of the abdomen or pelvis, a potential opportunity exists for concurrent BMD screening by QCT without the need for any additional imaging, radiation exposure, or patient time.

Clinical Use of Quantitative Computed Tomography-Based Advanced Techniques in the Management of Osteoporosis in Adults: the 2015 ISCD Official Positions-Part III

The International Society for Clinical Densitometry (ISCD) has developed new official positions for the clinical use of computed tomography (CT) scans acquired without a calibration phantom, for example, CT scans obtained for other diagnosis such as colonography. This also addresses techniques suggested for opportunistic screening of osteoporosis. The ISCD task force for quantitative CT reviewed the evidence for clinical applications of these new techniques and presented a report with recommendations at the 2015 ISCD Position Development Conference. Here we discuss the agreed upon ISCD official positions with supporting medical evidence, rationale, controversy, and suggestions for further study. Advanced techniques summarized as statistical parameter mapping methods were also reviewed. Their future use is promising but the clinical application is premature. The clinical use of QCT of the hip is addressed in part I and of finite element analysis of the hip and spine in part II.

Intravenous contrast injection significantly affects bone mineral density measured on CT

OBJECTIVE

The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications.

METHODS

One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1).

RESULTS

CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25% false negatives.

CONCLUSIONS

Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT.

KEY POINTS

• Routine CT may gain a role in bone attenuation measurements for osteoporosis • Contrast media injection has substantial influence on CT-derived bone density • Contrast-enhanced CT leads to underestimation of osteoporosis compared to unenhanced CT • Adjusting for contrast injection phase may improve CT screening protocols for osteoporosis.

Lateral tibial bone mineral density around the level of the proximal tibiofibular joint

PURPOSE

During open-wedge high tibial osteotomy, fracture occurring in the insufficient osteotomy before distraction of the osteotomy gap is an important complication. The objective of this study was to evaluate bone mineral density (BMD) around the proximal tibiofibular joint (PTFJ) and the osteotomy hinge. The hypotheses of this study were (1) BMD would be higher in the level of PTFJ, compared with that of above--or below--the level of PTFJ, (2) BMD of the posterolateral side of the hinge would be higher than that of the anterior or lateral side.

METHODS

Computed tomography was used to determine the BMD of the lateral aspect of the proximal tibia around the PTFJ and the osteotomy hinge. The means and standard deviations of the regions of interest were measured. To verify the first hypothesis, a coronal reconstructed image showing the beginning of the fibula head was used and an axial reconstructed image showing the beginning of the fibula head was used for verification of the second hypothesis.

RESULTS

BMD of the lateral aspect of the proximal tibia at the level of the PTFJ was significantly higher, compared with that of above (P = 0.04)-or below (P < 0.01)--the level of the PTFJ in male patients. In addition, it was also significantly higher, compared with that of below the level of the PTFJ (P < 0.01). BMD of the posterolateral area of the proximal tibia was significantly higher than that of the anterior or lateral area in both male and female patients (P < 0.01).

CONCLUSION

BMD of the level of the PTFJ was higher, compared with that of above-or below-the level of the PTFJ and that of the posterolateral area of the proximal tibia was significantly higher, compared with that of the anterior or lateral area.

Time dependency of bone density estimation from computed tomography with intravenous contrast agent administration

Our study has demonstrated that in contrast-enhanced multi-detector computed tomography (MDCT)-based bone density measurements, the scan delay time after contrast agent administration is a statistically significant variable for the derivation of quantitative computed tomography (QCT)-equivalent bone mineral density (BMD) values.

INTRODUCTION

Earlier investigators have proposed to derive QCT-equivalent BMD values from contrast-enhanced MDCT scans by using a merely density-based conversion equation. The purpose of this study was to investigate whether the scan delay after intravenous (IV) contrast agent administration might affect BMD values derived in this way.

METHODS

A retrospective data analysis was performed on 198 subjects who underwent standardized biphasic MDCT. Average densities values (in Hounsfield units) of lumbar vertebral bodies 1 to 3 (L1-L3) were compared between phases I and II of the biphasic MDCT scan. Furthermore, QCT-equivalent BMD (BMDQCT) values were calculated using a previously published conversion equation.

RESULTS

Paired t-test analysis revealed that IV contrast agent administration leads to a statistically significant increase (8.6 %; p < 0.0001) in overall density of L1-L3 from phases I to II. Moreover, comparison of BMDQCT values between phases I and II reveals a change from osteoporotic to osteopenic in 4.5 % of the study population and from osteopenic to normal for 11.1 % of the subjects. Furthermore, it was revealed that the density increase from phases I to II shows a weak, yet statistically significant (p < 0.001) age dependency.

CONCLUSIONS

Our study demonstrates that the use of a mere density-based conversion equation for deriving BMDQCT from MDCT scans ignores time dependency as an important variable. Furthermore, our results indicate that the actual age-dependent BMD itself might be another relevant variable that needs to be included in a MDCT-to-QCT conversion equation.

Tibial component coverage based on bone mineral density of the cut tibial surface during unicompartmental knee arthroplasty: clinical relevance of the prevention of tibial component subsidence

INTRODUCTION

An optimally implanted tibial component during unicompartmental knee arthroplasty would be flush with all edges of the cut tibial surface. However, this is often not possible, partly because the tibial component may not be an ideal shape or because the ideal component size may not be available. In such situations, surgeons need to decide between component overhang and underhang and as to which sites must be covered and which sites could be undercovered. The objectives of this study were to evaluate the bone mineral density of the cut surface of the proximal tibia around the cortical rim and to compare the bone mineral density according to the inclusion of the cortex and the site-specific matched evaluation.

MATERIALS AND METHODS

One hundred and fifty consecutive patients (100 men and 50 women) were enrolled in this study. A quantitative computed tomography was used to determine the bone density of the cut tibial surface. Medial and lateral compartments were divided into anterior, middle, and posterior regions, and these three regions were further subdivided into two regions according to containment of cortex. The site-specific matched comparison (medial vs. lateral) of bone mineral density was performed.

RESULTS

In medial sides, the mid-region, including the cortex, showed the highest bone mineral density in male and female patients. The posterior region showed the lowest bone mineral density in male patients, and the anterior and posterior regions showed the lowest bone mineral density in female patients. Regions including cortex showed higher bone mineral density than pure cancellous regions in medial sides. In lateral sides, posterior regions including cortex showed highest bone mineral density with statistical significance in both male and female patients. The anterior region showed the lowest bone mineral density in both male and female patients.

CONCLUSION

The mid-region of the medial side and the posterior region of the lateral side are relatively safe without cortical coverage when the component is not flush with all edges of the tibia. Cortical coverage is strongly recommended for the prevention of subsidence of the tibial component in the posterior region of the medial side, and in the anterior region of the lateral side.

Computed tomography based evaluation of the bone mineral density around the fixation area during knee ligament reconstructions: clinical relevance in the choice of fixation method

INTRODUCTION

This study examined the bone density around the fixation area during knee ligament reconstructions and assessed how this clinical relevance can be applied to a firm construction for a reconstructed ligament.

MATERIALS AND METHODS

Fifty consecutive patients (25 healthy men and 25 healthy women) were enrolled in this study. A quantitative computed tomography was used to determine the trabecular bone density at the 7 clinically relevant areas (anteromedial area of proximal tibia, anterolateral area of proximal tibia, posteromedial area of the proximal tibia, posterocentral area of the proximal tibia, posterolateral area of the proximal tibia, near femoral tunnel entrance of the ACL, near the femoral funnel entrance of the PCL). The means and standard deviations of the areas of interest were measured using a 10mm diameter circle and the bone density was compared.

RESULTS

A comparison of the fixation areas in the proximal tibia, anteromedial area of proximal tibia showed the highest bone density and posterocentral area showed the lowest bone density. A comparison of the PCL tibial fixation with interference screws or trans-condylar fixation revealed the posterocentral area to have the lowest bone density. A comparison of the femoral fixation areas in the ACL and PCL reconstruction revealed no differences in bone density.

CONCLUSION

The anteromedial area of the proximal tibia was most acceptable in the interference screw fixation and the posterocentral area had the lowest bone density in the proximal tibia. There were no differences in the femoral fixation areas in the ACL and PCL reconstruction.

Simultaneous screening for osteoporosis at CT colonography: bone mineral density assessment using MDCT attenuation techniques compared with the DXA reference standard

The purpose of this study was to evaluate the utility of lumbar spine attenuation measurement for bone mineral density (BMD) assessment at screening computed tomographic colonography (CTC) using central dual-energy X-ray absorptiometry (DXA) as the reference standard. Two-hundred and fifty-two adults (240 women and 12 men; mean age 58.9 years) underwent CTC screening and central DXA BMD measurement within 2 months (mean interval 25.0 days). The lowest DXA T-score between the spine and hip served as the reference standard, with low BMD defined per World Health Organization as osteoporosis (DXA T-score ≤ -2.5) or osteopenia (DXA T-score between -1.0 and -2.4). Both phantomless quantitative computed tomography (QCT) and simple nonangled region-of-interest (ROI) multi-detector CT (MDCT) attenuation measurements were applied to the T(12) -L(5) levels. The ability to predict osteoporosis and low BMD (osteoporosis or osteopenia) by DXA was assessed. A BMD cut-off of 90 mg/mL at phantomless QCT yielded 100% sensitivity for osteoporosis (29 of 29) and a specificity of 63.8% (143 of 224); 87.2% (96 of 110) below this threshold had low BMD and 49.6% (69 of 139) above this threshold had normal BMD at DXA. At L(1) , a trabecular ROI attenuation cut-off of 160 HU was 100% sensitive for osteoporosis (29 of 29), with a specificity of 46.4% (104 of 224); 83.9% (125 of 149) below this threshold had low BMD and 57.5% (59/103) above had normal BMD at DXA. ROI performance was similar at all individual T(12) -L(5) levels. At ROC analysis, AUC for osteoporosis was 0.888 for phantomless QCT [95% confidence interval (CI) 0.780-0.946] and ranged from 0.825 to 0.853 using trabecular ROIs at single lumbar levels (0.864; 95% CI 0.752-0.930 at multivariate analysis). Supine-prone reproducibility was better with the simple ROI method compared with QCT. It is concluded that both phantomless QCT and simple ROI attenuation measurements of the lumbar spine are effective for BMD screening at CTC with high sensitivity for osteoporosis, as defined by the DXA T-score.

BMD measurements of the spine derived from sagittal reformations of contrast-enhanced MDCT without dedicated software

PURPOSE

To assess QCT equivalent BMD of the lumbar spine in sagittal reformations of routine abdominal contrast-enhanced MDCT with simple PACS measurement tools and to apply this method to MDCT datasets for differentiating patients with and without osteoporotic vertebral fractures.

MATERIALS AND METHODS

Eight postmenopausal women (65±5 years) underwent standard QCT to assess BMD of L1-L3. Afterwards routine abdominal contrast-enhanced MDCT images of these women were obtained and apparent BMD of L1-L3 was measured using the sagittal reformations. The MDCT-to-QCT conversion equation for BMD was calculated with linear regression analysis. The conversion equation was applied to vertebral BMD datasets (L1-L3) of 75 postmenopausal women (66±4 years). Seventeen of the 75 patients had osteoporotic vertebral fractures.

RESULTS

BMD values of contrast-enhanced MDCT were on average 56 mg/ml higher than those of standard QCT. A correlation coefficient of r=0.94 (p<0.05) was calculated for the BMD values of MDCT and standard QCT with the conversion equation BMDQCT=0.69×BMDMDCT-11 mg/ml. Accordingly converted BMD values of patients with vertebral fractures were significantly lower than those of patients without vertebral fractures (69 mg/ml vs. 85 mg/ml; p<0.05). Using ROC analysis to differentiate patients with and without vertebral fractures, AUC=0.72 was obtained for converted BMD values (p<0.05). Short- and long-term reproducibility errors for BMD measurements in the sagittal reformations amounted 2.09% and 7.70%, respectively.

CONCLUSION

BMD measurements of the spine could be computed in sagittal reformations of routine abdominal contrast-enhanced MDCT with minimal technical and time effort. Using the conversion equation, the acquired BMD data could differentiate patients with and without osteoporotic vertebral fractures.

Femoral head density on CT scans of patients following hip fracture fixation by expandable proximal peg or dynamic screw

Computed tomography (CT) is currently considered to be an accurate method for evaluating bone density. We evaluated the CT measurements of bone density using the Hounsfield units (HUs) in 23 patients who had been operated in the past for an extra-capsular hip fracture. Twelve patients were treated with a dynamic hip screw and 11 with a proximal femoral expandable hip nail. All the CTs had been performed for non-orthopedic purposes. Bone density with a region of interest (ROI) could be assessed for both hips. We compared the bone density between the operated versus the non-operated sides as well as between the two surgical groups. Bone density was higher in the hip peg (the femoral component of the expandable nail) side 262.5 (range, 169-351) HU, compared to the opposite non-operated side and to the hip screw group 194 (range, 99-283) HU. The hip screw side had decreased bone density compared to the opposite non-operated side. We were able to define a density index and a difference index: both were higher in the hip peg group. These findings persisted over time. It would be interesting to speculate that increased bone density around an expandable peg provides better fracture stabilization and probably faster healing than a dynamic hip screw.

Can abdominal multi-detector CT diagnose spinal osteoporosis?

The aim of this study was to (1) generate quantitative CT (QCT) densitometric data based on routine abdominal multi-detector (MDCT) examinations and (2) investigate whether these data can be used to differentiate osteoporotic from healthy females. Twenty-five female patients (group A) with a history of radiotherapy were examined both with routine abdominal MDCT and standard QCT to generate a MDCT-to-QCT conversion equation. Twenty-one osteoporotic (group B) and 23 healthy female patients (group C) were also recruited in the study. Patients of groups B and C underwent routine abdominal MDCT examination for various clinical indications. Mean bone mineral density (BMD) in patients of group A was 103.4 mg/ml +/- 32.8 with routine abdominal MDCT and 91.0 mg/ml +/- 28.5 with QCT. Quantitative CT BMD(QCT) values for patients in groups B and C were calculated utilizing the BMD(MDCT) values derived from routine abdominal MDCT data sets and the MDCT to QCT conversion equation: BMD(QCT)=0:78 x BMD(MDCT) + 10:13. The calculated QCT densitometric data adequately differentiated osteoporotic from healthy females (area under ROC curve 0.828, p = 0.05). In conclusion, this study showed that in a group of female patients, QCT data derived from routine abdominal MDCT examinations discriminated osteoporotic from healthy subjects.

Volumetric quantitative CT of the spine and hip derived from contrast-enhanced MDCT: conversion factors

OBJECTIVE

The purposes of this study were to perform volumetric quantitative CT (QCT) of the spine and hip using nondedicated contrast-enhanced standard MDCT data sets and to derive a conversion factor for bone mineral density (BMD) assessment based on dedicated volumetric QCT data sets.

SUBJECTS AND METHODS

Forty postmenopausal women with a mean +/- SD age of 71 +/- 9 years underwent routine contrast-enhanced abdominal and pelvic MDCT. Before this imaging examination, standard volumetric QCT of the spine (L1-L3, n = 40) and hip (n = 21) was performed. Relations between QCT and contrast-enhanced MDCT findings were assessed with linear regression analysis.

RESULTS

Mean lumbar BMD was 84.1 +/- 35.8 mg/mL, and mean femoral BMD was 0.62 +/- 0.12 g/cm2, as determined with QCT. Contrast-enhancement values with MDCT were on average 30.3% higher than those of QCT in the spine and 2.3% higher in the proximal femur (p < 0.05). Based on linear regression, a correlation coefficient of r = 0.98 was calculated for lumbar BMD with the equation BMD(QCT) = 0.96xBMD(MDCT) - 20.9 mg/mL. A coefficient of r = 0.99 was calculated for the proximal femur with the equation BMD(QCT) = 0.99xBMD(MDCT) - 12 mg/cm2 (p < 0.01). In 17 of 40 patients, 33 vertebral fractures were found. The dedicated QCT and enhanced MDCT data sets did not show a significant difference (p > 0.05) between patients with fractures and those without fractures.

CONCLUSION

With the conversion factors, reliable volumetric BMD measurements can be calculated for the hip and the spine from routine abdominal and pelvic MDCT data sets.

Neue Techniken in der Osteoporosediagnostik

In this review article current developments and applications in quantitative osteoporosis imaging are presented. Developments in the field of DXA include geometrical parameters of the proximal femur such as the "hip axis length" and new ROIs to determine BMD. Advances in QCT are new volumetric techniques to quantify BMD at the lumbar spine and the proximal femur. In addition techniques to determine BMD in standard contrast-enhanced abdominal computed tomography studies are described. Currently with the new bone quality concept in full bloom techniques to quantify trabecular bone architecture as new surrogates of bone strength are of increasing significance. Spatial high-resolution techniques such as magnetic resonance imaging and new computed tomography techniques have shown their potential in assessing trabecular bone structure. In addition ultrasound is considered a low-cost technique to explore bone quality.

Bone mineral density of the proximal metaphysis of tibia: clinical relevance in posterior cruciate ligament reconstruction

The objective of this study was to evaluate the bone mineral density (BMD) of the proximal tibia in the area adjacent to the fixation of the posterior cruciate ligament (PCL) and compare with the BMD in a similar area at the ideal site for anterior cruciate ligament fixation. Twenty healthy male subjects, undertaking similar daily physical activity were enrolled for this study. The mean age of the subjects was 22 years (range 20-24 years). The bone mineral density (BMD) at the proximal tibia was calculated using a quantitative CT scan of the dominant knee, and the data were recorded in Hounsfield units (HU). Two circular regions of interest, anterior and posterior, of identical diameters (10 mm) and thicknesses (5 mm) were studied. The results showed a significantly higher BMD in the anterior region (162.4 +/- 33.8 HU) than in the posterior one (104 +/- 24.6 HU) with a statistically significant difference (p=0.0001). The clinical implication of this finding is that the fixation should provide a firm construct for PCL reconstructions and be specifically designed for working in low bone quality areas such as the posterior proximal tibia.

In vitro and in vivo spiral CT to determine bone mineral density: initial experience in patients at risk for osteoporosis

PURPOSE

To evaluate, both experimentally and in vivo, if nondedicated standard spiral computed tomography (CT) may be used to obtain reliable bone mineral density (BMD) data.

MATERIALS AND METHODS

Twenty lumbar spine specimens from human cadavers were examined with standard quantitative CT and spiral CT. In addition, 50 patients with a history of lymphoma and chemotherapy were examined. These patients underwent long-term follow-up CT to rule out tumor recurrence. Quantitative CT was performed before contrast medium administration to assess potential posttherapeutic osteoporosis. In addition, fracture status of the spine was determined. Mean BMD values and SDs were calculated, and relationships between measurements obtained with quantitative CT and spiral CT were assessed with linear regression analysis and two-tailed tests of significance (t test). A linear fit was used to calculate quantitative CT data from spiral CT values.

RESULTS

For the specimens, a coefficient of determination (r(2) = 0.99, P <.001) was found between BMD measurements obtained with quantitative CT and those obtained with spiral CT. Mean BMD in specimens was 63.6 mg/mL +/- 36.6 with quantitative CT and 74.4 mg/mL +/- 38.2 with spiral CT. Mean BMD in patients was 105.0 mg/mL +/- 34.6 with quantitative CT and 139.5 mg/mL +/- 42.7 with contrast medium-enhanced spiral CT. A coefficient of determination (r(2) = 0.91, P <.001) was obtained between these measurements. Mean BMD from L1 through L3 vertebrae was calculated, and spiral CT data were multiplied by 0.77 to yield quantitative CT data. Differences in BMD were significant (P <.05) for patients with (n = 9) and those without fractures (n = 41), as determined with spiral CT and quantitative CT.

CONCLUSION

Correlations between BMD data obtained with spiral CT and standard quantitative CT were highly significant. By using a conversion factor, BMD measurements can be determined with routine abdominal spiral CT scans.

Efficacy of radioprotection in the prevention of radiation-induced craniofacial bone growth inhibition

It has been reported that radiotherapy-induced craniofacial deformities can occur in 66 to 100 percent of survivors of childhood head and neck cancers. Recent interest in the effectiveness of radioprotectors in the protection of normal tissue against radiation injury led us to investigate a possible role of radioprotection in the prevention of radiation-induced craniofacial bone growth inhibition. Therefore, the objective of this study was to use the radioprotective agent amifostine (Ethyol, WR-2721) as a probe to determine the effectiveness of radioprotection in the prevention of radiation-induced craniofacial bone growth inhibition after single-dose orthovoltage radiation to the infant rabbit orbital-zygomatic complex. Seven-week-old male New Zealand white rabbits were randomized into three groups (n = 10 each): group 1, 0 Gy (sham radiation); group 2, 35-Gy single-dose orthovoltage radiation; and group 3, 35-Gy single-dose orthovoltage radiation and amifostine (300 mg/kg intravenously, given 20 minutes before radiation). Serial radiographs and computed tomographic scans were obtained for cephalometric analysis, bone volume, and bone density measurements until skeletal maturity at 21 weeks. Significant (p < 0.05) reductions in orbital-zygomatic complex linear bone growth, bone volume, and bone density were observed after 35-Gy radiation compared with nonirradiated controls. No significant differences were noted between groups in cephalometric analysis of the nontreated (nonirradiated) left orbital-zygomatic complex, indicating no crossover effect from the radiation beam. However, pretreatment with amifostine, 20 minutes before 35-Gy radiation, resulted in significant (p < 0.05) preservation of linear bone growth, bone volume, and bone mineral density in the rabbit orbital-zygomatic complex compared with controls. This study demonstrated for the first time the effectiveness of a radioprotector in the prevention of radiation-induced craniofacial bone growth inhibition, and it paves the way for investigation into the pathogenic mechanism and prevention of radiotherapy-induced craniofacial deformities.