Investigating comparability of quantitative computed tomography with dual energy x-ray absorptiometry in assessing bone mineral density of patients with chronic spinal cord injury

MSC-Based Cell Therapy in Neurological Diseases: A Concise Review of the Literature in Pre-Clinical and Clinical Research

Mesenchymal stem cells (MSCs) are multipotent stromal cells with the ability to self-renew and multi-directional differentiation potential. Exogenously administered MSCs can migrate to damaged tissue sites and participate in the repair of damaged tissues. A large number of pre-clinical studies and clinical trials have demonstrated that MSCs have the potential to treat the abnormalities of congenital nervous system and neurodegenerative diseases. Therefore, MSCs hold great promise in the treatment of neurological diseases. Here, we summarize and highlight current progress in the understanding of the underlying mechanisms and strategies of MSC application in neurological diseases.

Can You Feel it? - Correlation Between Intraoperatively Perceived Bone Quality and Objectively Measured Bone Mineral Density

STUDY DESIGN

clinical study.

OBJECTIVES

Loosening of pedicle screws is a frequent complication in patients with osteoporosis. The indication for additional stabilization, such as cement augmentation, is more often based on the subjective intraoperative feeling of the surgeon than on a preoperative bone mineral density (BMD) measurement. Aim was to evaluate the correlation of the intraoperative perceived bone quality in comparison to the objectively measured BMD.

METHODS

A total of 62 patients undergoing dorsal stabilization using pedicle screws at a level-1 trauma center were analyzed. The preoperative CT scan measured each instrumented vertebra's pedicle size and BMD. During the surgery, the perceived screw stability was graded by the respective surgeon for each screw.

RESULTS

204 vertebral bodies were evaluated. Looking at all implanted screws a significant correlation between the measured BMD and the perceived screw stability was found (Resident r = .450; R2 = .202; P < .001/Attending r = .364; R2 = .133; P < .001), but there was no significant correlation in the osteoporotic patients (Resident P = .148 / Attending P = .907). The evaluation of the screws implanted in osteoporotic vertebrae showed that the surgeons considered a total of 31% of these screws to be sufficiently stable.

CONCLUSIONS

There was no significant correlation between the measured BMD and the perceived pedicle screw stability in the group with osteopenic / osteoporotic bone (<100 mg/cm³). The results indicate that it is not possible to reliably determine the bone quality and the resulting screw stability in patients with reduced BMD. The preoperative measurement of the BMD should become a crucial part of preoperative planning.

Effect of a Contrast Agent on Bone Mineral Density Measurement in the Spine and Hip Using QCT-Conversion Factor Recommendation

BACKGROUND

Osteoporosis causes an increased fracture risk. Clinically, osteoporosis is diagnosed late, usually after the first fracture occurs. This emphasizes the need for an early diagnosis of osteoporosis. However, computed tomography (CT) as routinely used for polytrauma scans cannot be used in the form of quantitative computed tomography (QCT) diagnosis because QCT can only be applied natively, i.e., without any contrast agent application. Here, we tested whether and how contrast agent application could be used for bone densitometry measurements.

METHODS

Bone mineral density (BMD) was determined by QCT in the spine region of patients with and without the contrast agent Imeron 350. Corresponding scans were performed in the hip region to evaluate possible location-specific differences.

RESULTS

Measurements with and without contrast agent administration between spine and hip bones indicate that the corresponding BMD values were reproducibly different between spine and hips, indicating that Imeron 350 application has a location-specific effect. We determined location-specific conversion factors that allow us then to determine the BMD values relevant for osteoporosis diagnosis.

CONCLUSIONS

Results show that contrast administration cannot be used directly for CT diagnostics because the agent significantly alters BMD values. However, location-specific conversion factors can be established, which are likely to depend on additional parameters such as the weight and corresponding BMI of the patient.

MicroRNA-451 Attenuates the Inflammatory Response of Activated Microglia by Downregulating Nucleotide Binding Oligomerization Domain-Like Receptor Protein 3

BACKGROUND

Spinal cord injury is the most common problem encountered during spinal surgery. After the initial trauma, the disruption of the blood-brain barrier and subsequent microglia activation result in extensive inflammatory responses. Inflammasomes are large protein complexes that are essential during inflammation. One of the most studied inflammasome components, nucleotide binding oligomerization domain-like receptor protein 3 (NLRP; nucleotide binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing 3), is widely expressed in the central nervous system. Previous research has shown that microRNA-451 (miR-451) might play a role in regulating inflammatory conditions.

METHODS

Using bioinformatics analysis, we found that NLRP3 is a direct target of miR-451. This in silico prediction was confirmed using dual-luciferase reporter gene assays. To further demonstrate that miR-451 influenced microglial NLRP3 production, we activated microglial cells with lipopolysaccharides.

RESULTS

Activating microglial cells with lipopolysaccharides resulted in the production of NLRP3 inflammasomes and the secretion of the proinflammatory cytokines interleukin-1β and interleukin-18. We were able to demonstrate that overexpression of miR-451 suppressed this NLRP3-induced proinflammatory cascade of events.

CONCLUSIONS

Our findings have highlighted the potential anti-inflammatory role of miR-451 in reducing the secondary neuronal damage after spinal cord injury.

Efficacy of Hounsfield Units Measured by Lumbar Computer Tomography on Bone Density Assessment: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

This work aimed to compare the Hounsfield units (HU) value obtained from computed tomography and the t score of dual-energy x-ray absorptiometry (DXA) in the prediction of the lumbar spine bone mineral density (BMD).

SUMMARY OF BACKGROUND DATA

Several reports have found a correlation between HU and BMD values based on DXA. Using HUs to infer bone quality has a thorough clinical relevance as it could triage patients at risk for osteoporotic and fragility fractures or modify surgical indications.

METHODS

A systematic review in Cochrane Library, Medline, Scopus and Web of Science was performed, using the following query: "hounsfield units" AND ("osteoporosis" OR "spine" OR "bone mineral density" OR "dual x-ray absorptiometry"). We included 18 cohort studies that compared HU value obtained from computed tomography and t score of DXA for predicting regional BMD.

RESULTS

A total of 18 studies were included, enrolling 5307 patients. The HU measurement was most frequently made at L1 (N = 3; 18.8%). The mean HU values differentiated based on BMD measured through DXA were reported in seven studies, with values from 54.7 to 130 for osteoporotic, 78.8 to 146 for osteopenic, and from 120.8 to 230 in normal patients. Eight studies identified thresholds for diagnosing osteoporosis through receiver-operating characteristic (ROC) curves, with values ranging from 0.66 to 0.96. Medium HU values reported as diagnostic of osteoporosis ranged between 110 and 150, after exclusion of the two papers presenting outlier values. We infer an HU interval value of 90.9 to 138.7 (95% CI, P  < 0.001) for the diagnosis osteoporosis.

CONCLUSIONS

Present data evidence favorable results regarding the possibility of establishing a threshold value for osteoporosis diagnosis from CT measurements of HU. Prospective large-scale studies are needed to more robustly infer the possibility of quantifying BMD based on CT as a screening test and infer a prognostic value of the CT-based evaluation.Level of Evidence: 2.