Correlation between bone density measurements on CT or MRI versus DEXA scan: A systematic review

Optimizing bone marrow harvesting sites for enhanced mesenchymal stem cell yield and efficacy in knee osteoarthritis treatment

Knee osteoarthritis (OA) is a debilitating condition with limited long-term treatment options. The therapeutic potential of mesenchymal stem cells (MSCs), particularly those derived from bone marrow aspirate concentrate, has garnered attention for cartilage repair in OA. While the iliac crest is the traditional site for bone marrow harvesting (BMH), associated morbidity has prompted the exploration of alternative sites such as the proximal tibia, distal femur, and proximal humerus. This paper reviews the impact of different harvesting sites on mesenchymal stem cell (MSC) yield, viability, and regenerative potential, emphasizing their relevance in knee OA treatment. The iliac crest consistently offers the highest MSC yield, but alternative sites within the surgical field of knee procedures offer comparable MSC characteristics with reduced morbidity. The integration of harvesting techniques into existing knee surgeries, such as total knee arthroplasty, provides a less invasive approach while maintaining therapeutic efficacy. However, variability in MSC yield from these alternative sites underscores the need for further research to standardize techniques and optimize clinical outcomes. Future directions include large-scale comparative studies, advanced characterization of MSCs, and the development of personalized harvesting strategies. Ultimately, the findings suggest that optimizing the site of BMH can significantly influence the quality of MSC-based therapies for knee OA, enhancing their clinical utility and patient outcomes.

Age-dependent changes in CT vertebral attenuation values in opportunistic screening for osteoporosis: a nationwide multi-center study

OBJECTIVES

To examine how vertebral attenuation changes with aging, and to establish age-adjusted CT attenuation value cutoffs for diagnosing osteoporosis.

MATERIALS AND METHODS

This multi-center retrospective study included 11,246 patients (mean age ± standard deviation, 50 ± 13 years; 7139 men) who underwent CT and dual-energy X-ray absorptiometry (DXA) in six health-screening centers between 2022 and 2023. Using deep-learning-based software, attenuation values of L1 vertebral bodies were measured. Segmented linear regression in women and simple linear regression in men were used to assess how attenuation values change with aging. A multivariable linear regression analysis was performed to determine whether age is associated with CT attenuation values independently of the DXA T-score. Age-adjusted cutoffs targeting either 90% sensitivity or 90% specificity were derived using quantile regression. Performance of both age-adjusted and age-unadjusted cutoffs was measured, where the target sensitivity or specificity was considered achieved if a 95% confidence interval encompassed 90%.

RESULTS

While attenuation values declined consistently with age in men, they declined abruptly in women aged > 42 years. Such decline occurred independently of the DXA T-score (p < 0.001). Age adjustment seemed critical for age ≥ 65 years, where the age-adjusted cutoffs achieved the target (sensitivity of 91.5% (86.3-95.2%) when targeting 90% sensitivity and specificity of 90.0% (88.3-91.6%) when targeting 90% specificity), but age-unadjusted cutoffs did not (95.5% (91.2-98.0%) and 73.8% (71.4-76.1%), respectively).

CONCLUSION

Age-adjusted cutoffs provided a more reliable diagnosis of osteoporosis than age-unadjusted cutoffs since vertebral attenuation values decrease with age, regardless of DXA T-scores.

KEY POINTS

Question How does vertebral CT attenuation change with age? Findings Independent of dual-energy X-ray absorptiometry T-score, vertebral attenuation values on CT declined at a constant rate in men and abruptly in women over 42 years of age. Clinical relevance Age adjustments are needed in opportunistic osteoporosis screening, especially among the elderly.

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.

Prediction of screw loosening by measuring the insertion torque in non-osteoporotic patients: an in vitro study

BACKGROUND

Pedicle screws are commonly used in spinal surgeries, but screw loosening remains a major concern, even in non-osteoporotic patients. Predicting pedicle screw stability via the insertion torque is a controversial topic, mainly studied on osteoporotic cadavers. Whether the insertion torque is suitable for patients with healthy bone mineral density (BMD) remains unknown. The aim was to investigate the influencing factors, namely insertion torque, BMD, screw diameter, length, surface area, volume, screw-in rotations, vertebral level, on the screw loosening stability during distractions and to understand if intra-operative predictions are possible.

METHODS

Non-osteoporotic thoraco-lumbar vertebrae (n = 50) were used to implant five different pedicle screws (n = 100) while measuring the insertion torque. After embedding the endplates, the force needed to distract the screw head by 1 mm was tested.

RESULTS

The insertion toque (2.3 ± 0.9 Nm) showed the highest influence on the distraction force (324.8 ± 84.4 N) followed by the screw size and vertebral level. BMD did not show any effects.

CONCLUSIONS

The linear correlation of insertion torque and the bending force suggests an alternative prediction metric for screw loosening which could improve the outcome of surgeries and patients' safety. This is potentially a simple, intra-operative method, which can be used in future.

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.

Decrease in Facial Bone Density with Aging and Maintenance Effect of Calcium Maltobionate Ingestion in Japanese Adult Women: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Trial

BACKGROUND/OBJECTIVES

Facial bone density, including the jawbone, declines earlier than that of the lumbar spine and calcaneus. Calcium maltobionate is reported to mitigate bone resorption and maintain bone density of the lumbar spine in post-menopausal women, but its effects on facial bone density remain understudied. Therefore, this study compared variations in facial bone mineral density with variations in calcaneal bone mineral density and bone resorption markers among healthy women, examining differences between pre- and post-menopause and the effects of continuous calcium maltobionate intake.

METHODS

This randomized, double-blind, placebo-controlled, parallel-group trial involved 48 healthy Japanese women aged 30-69 years, divided into two groups. The test food group received tablets containing calcium maltobionate, while the placebo group received tablets containing a maltose and calcium carbonate mixture for 24 weeks. Calcaneal and facial bone densities were measured pre- and post-intervention in both groups.

RESULTS

Post-intervention calcaneal bone mineral density and bone resorption marker deoxypyridinoline (DPD) showed no statistical difference between groups in pre-menopausal women. However, in post-menopausal women, the test food group exhibited significantly higher calcaneal bone density and lower DPD levels compared with the placebo group. Facial bone mineral density increased significantly in the test food group compared with the placebo group in post-menopausal participants, with similar trends observed in pre-menopausal participants.

CONCLUSIONS

Facial bone mineral density could serve as a useful indicator for monitoring bone health from middle age onward. Moreover, continuous calcium maltobionate intake appears to mitigate bone density decline in pre- and post-menopausal women, contributing to osteoporosis prevention (UMIN-CTR ID: 000046391).

Low bone mineral density: a primer for the spine surgeon

Within spinal surgery, low bone mineral density is associated with several postoperative complications, such as proximal junctional kyphosis, pseudoarthrosis, and screw loosening. Although modalities such as CT and MRI can be utilized to assess bone quality, DEXA scans, the "Gold Standard" for diagnosing osteoporosis, is not routinely included in preoperative workup. With an increasing prevalence of osteoporosis in an aging population, it is critical for spine surgeons to understand the importance of evaluating bone mineral density preoperatively to optimize postoperative outcomes. The purpose of this state-of-the-art review is to provide surgeons a summary of the evaluation, treatment, and implications of low bone mineral density in patients who are candidates for spine surgery.

Vertebral bone quality score as a new tool for osteoporosis diagnosis in patients undergoing lumbosacral fusion surgery: a single center cohort study

Osteoporosis, a common bone disorder, increases fracture and spinal surgery complications risk. This study evaluates the potential of the Magnetic Resonance Imaging (MRI)-based Vertebral Bone Quality (VBQ) score as an alternative for assessing bone density in lumbosacral fusion surgery patients. In a prospective cohort study from April 2021 to November 2022, 134 patients with lumbar degenerative diseases underwent lumbar Dual-Energy X-ray Absorptiometry (DXA) and lumbosacral non-contrast T1-weighted MRI. VBQ scores were calculated and analyzed using IBM SPSS Statistics and MedCalc software. Osteopenia/Osteoporosis patients exhibited significantly higher VBQ scores than normal bone mineral density patients (3.37 ± 0.51 vs. 2.99 ± 0.44, P<0.001). VBQ correlated significantly with lumbar DXA T scores (r value= -0.415, p<0.001). Receiver Operating Characteristic (ROC) analysis showed VBQ AUC values of 0.730 (CI 95% 0.647-0.803, P<0.001) and 0.839 (CI 95% 0.765-0.897, P<0.001) for Osteopenia/Osteoporosis and osteoporosis diagnosis, respectively. The study suggests MRI-derived VBQ scores may benefit pre-lumbosacral fusion surgery bone density assessment, potentially improving patient care and aiding osteoporosis detection in spinal surgery candidates.

Inter and intra-operator reliability of Lekholm and Zarb classification and proposal of a novel radiomic data-driven clustering for qualitative assessment of edentulous alveolar ridges

OBJECTIVES

The present study was conducted to evaluate the reproducibility of Lekholm and Zarb classification system (L&Z) for bone quality assessment of edentulous alveolar ridges and to investigate the potential of a data-driven approach for bone quality classification.

MATERIALS AND METHODS

Twenty-six expert clinicians were asked to classify 110 CBCT cross-sections according to L&Z classification (T0). The same evaluation was repeated after one month with the images put in a different order (T1). Intra- and inter-examiner agreement analyses were performed using Cohen's kappa coefficient (CK) and Fleiss' kappa coefficient (FK), respectively. Additionally, radiomic features extraction was performed from 3D edentulous ridge blocks derived from the same 110 CBCTs, and unsupervised clustering using 3 different clustering methods was used to identify patterns in the obtained data.

RESULTS

Intra-examiner agreement between T0 and T1 was weak (CK 0.515). Inter-examiner agreement at both time points was minimal (FK at T0: 0.273; FK at T1: 0.243). The three different unsupervised clustering methods based on radiomic features aggregated the 110 CBCTs in three groups in the same way.

CONCLUSIONS

The results showed low agreement among clinicians when using L&Z classification, indicating that the system may not be as reliable as previously thought. The present study suggests the possible application of a reproducible data-driven approach based on radiomics for the classification of edentulous alveolar ridges, with potential implications for improving clinical outcomes. Further research is needed to determine the clinical significance of these findings and to develop more standardized and accurate methods for assessing bone quality of edentulous alveolar ridges.

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.

Coronal plane in opportunistic screening of osteoporosis using computed tomography: comparison with axial and sagittal planes

OBJECTIVE

To compare the coronal plane with axial and sagittal planes in opportunistic screening of osteoporosis using computed tomography (CT).

MATERIALS AND METHODS

A total of 100 patients aged ≥ 50 years who underwent both lumbar spine CT and dual-energy X-ray absorptiometry within 3 months were included. Osteoporosis was diagnosed based on dual-energy X-ray absorptiometry results. The CT number was measured at the center of the vertebral body in coronal, axial, and sagittal planes. To compare the coronal plane with axial and sagittal planes in diagnosing osteoporosis, the areas under the receiver operating characteristic curve (AUC) were compared and intraclass correlation coefficient (ICC) was calculated. The optimal cutoff values were calculated using Youden's index.

RESULTS

The AUC of the coronal plane (0.80; 95% confidence interval [CI], 0.71-0.89) was not significantly different from that of the axial plane (0.78; 95% CI, 0.68-0.87; P = 0.39) and that of the sagittal plane (0.78; 95% CI, 0.69-0.87; P = 0.68). Excellent concordance rates were observed between coronal and axial planes with ICC of 0.95 (95% CI, 0.92-0.96) and between coronal and sagittal planes with ICC of 0.93 (95% CI, 0.85-0.96). The optimal cutoff values for the coronal, axial, and sagittal planes were 110, 112, and 112 HU, respectively.

CONCLUSION

The coronal plane does not significantly differ from axial and sagittal planes in opportunistic screening of osteoporosis. Thus, the coronal plane as well as axial and sagittal planes can be used interchangeably in measuring bone mineral density using CT.