Diagnostic Tools and Imaging Methods in Intervertebral Disk Degeneration
Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94158, USA.Orthopedic Clinics of North America (Impact Factor: 1.25). 10/2011; 42(4):501-11, viii. DOI: 10.1016/j.ocl.2011.07.007
Low back pain has a negative impact on the economy and society. Intervertebral disk degeneration is linked to the occurrence of low back pain. MRI provides three-dimensional morphologic and biochemical information regarding the status of the disk. This article reviews new and evolving MRI disk-imaging techniques, including grading, relaxation-time measurements, diffusion, and contrast perfusion. In addition, high-resolution magic-angle spinning methods to correlate in vitro disk degeneration (with pain, etc) and in vivo spectroscopic results are discussed. With the potential for morphologic and biochemical characterization of the intervertebral disk, MRI shows promise as a tool to quantitatively assess disk health.
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ABSTRACT: Purpose: To image human disk-bone specimens by using conventional spin-echo (SE) and ultrashort echo time (TE) techniques, to describe the morphology at magnetic resonance (MR) imaging, and to identify tissue components contributing to high signal intensity near the cartilaginous endplates (CEPs). Materials and methods: This study was exempt from institutional review board approval, and informed consent was not required. Five cadaveric lumbar spines (mean age, 61 years ± 11) were prepared into six sample types containing different combinations of disk, uncalcified CEP, calcified CEP, and subchondral bone components and were imaged with proton density-weighted SE (repetition time msec/TE msec, 2000/15) and ultrashort TE (300/0.008, 6.6, echo-subtraction) sequences. Images were evaluated to determine the presence of intermediate-to-high signal intensity in regions excluding the bone marrow. Logistic regression was used to determine which tissue components were significant predictors of the presence of signal intensity for each MR technique. Results: On ultrashort TE MR images, intact disk/uncalcified CEP/calcified CEP/bone samples exhibited bilaminar intermediate-to-high signal intensity in the region near the CEP, consistent with the histologic appearance of uncalcified and calcified CEPs. Conversely, proton density-weighted SE images exhibited low signal intensity in this region. Results of logistic regression suggested that the presence of uncalcified CEP (P = .023) and calcified CEP (P = .007) in the sample were strong predictors of the presence of signal intensity on ultrashort TE images, whereas the disk was the only predictor (P < .001) of signal intensity on proton density-weighted SE images. Conclusion: Ultrashort TE imaging, unlike proton density-weighted SE imaging, enabled direct visualization of the uncalcified and calcified CEP. Evaluation of the morphology and identification of sources of signal intensity at ultrashort TE MR imaging provides opportunities to potentially aid in the understanding of degenerative disk disease.Radiology 11/2012; 266(2). DOI:10.1148/radiol.12121181 · 6.87 Impact Factor
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ABSTRACT: Introduction: Link N is a naturally occurring peptide that can stimulate proteoglycan synthesis in intervertebral disc (IVD) cells. IVD repair can also potentially be enhanced by mesenchymal stem cell (MSC) supplementation to maximize extracellular matrix production. In a previous study we have shown that Link N can inhibit osteogenesis and increase the chondrogenesis of MSCs in vitro. The aim of the present study was to determine the potential of MSCs and Link N alone or together on the repair the degenerate discs. Materials and Methods: Bovine IVDs with trypsin-induced degeneration were treated with MSCs, Link N or a combination of MSCs and Link N. Trypsin-treated discs were also injected with PBS to serve as a degeneration control. The extracellular matrix (ECM) proteins and proteoglycans were extracted from the inner nucleus pulposus of the discs and sulfated glycosaminoglycans (GAGs) were analyzed by the dimethyl methylene blue (DMMB) dye-binding assay. The expression of type II collagen was analyzed by western blot. To track the MSCs after injection, MSCs were labeled with PKH67 and observed under confocal microscopy after the two week culture period. Results: The GAG content significantly increased compared to the degeneration control when degenerate discs were treated with MSCs, Link N or with a combination of both Link N and MSCs. Histological analysis revealed that the newly synthesized proteoglycan was able to diffuse throughout the ECM and restore tissue content even in areas remote from the cells. The quantity of extractable type II collagen was also increased when the degenerate discs were treated with MSCs and Link N, either alone or together. MSCs survived and integrated in the tissue and were found distributed throughout the nucleus pulposus after the two week culture period. Conclusion: MSCs and Link N can restore GAG content in degenerate discs, when administered separately or together. Treatment with MSCs and Link N can also increase the expression of type II collagen. The results support the concept that biological repair of disc degeneration is feasible, and that the administration of either MSCs or Link N has therapeutic potential in early stages of the disease.Tissue Engineering Part A 04/2014; 20(21-22). DOI:10.1089/ten.TEA.2013.0749 · 4.64 Impact Factor
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ABSTRACT: This study aims to: (1) measure the shear modulus of nucleus pulposus (NP) in intact human vertebra-disc-vertebra segments using a magnetic resonance elastography setup for a 7T whole-body scanner, (2) quantify the effect of disc degeneration on the NP shear modulus measured using magnetic resonance elastography, and (3) compare the NP shear modulus to other magnetic resonance-based biomarkers of dis degeneration. Thirty intact human disc segments were classified as normal, mild, or severely degenerated. The NP shear modulus was measured using a custom-made setup that included a novel inverse method less sensitive to noisy displacements. T2 relaxation time was measured at 7T. The accuracy of these parameters to classify different degrees of degeneration was evaluated using receiver operating characteristic curves. The magnetic resonance elastography measure of shear modulus in the NP was able to differentiate between normal, mild degeneration, and severe degeneration. The T2 relaxation time was able to differentiate between normal and mild degeneration, but it could not distinguish between mild and severe degeneration. This study shows that the NP shear modulus measured using magnetic resonance elastography is sensitive to disc degeneration and has the potential of being used as a clinical tool to quantify the mechanical integrity of the intervertebral disc. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.Magnetic Resonance in Medicine 07/2014; 72(1). DOI:10.1002/mrm.24895 · 3.57 Impact Factor
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