Assessment of lumbar disc herniaton using fractional anisotropy in diffusion tensor imaging along with conventional T2-weighted imaging

Longitudinal DTI analysis of microstructural changes in lumbar nerve roots following Interspinous process device placement

Diffusion tensor imaging (DTI) and its parameters such as fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) are increasingly being used to assess peripheral nerve integrity alongside nerve conduction studies. This pilot study aims to compare DTI values of lumbar spinal nerve roots before (T0) and after (T1) treatment with an interspinous process device (IPD). Seven patients (5 females, 2 males; mean age: 68) suffering from neurogenic claudication and lumbar spinal canal and foraminal stenosis were evaluated. Visual Analog Scale (VAS) for perceived pain, Oswestry Disability Index (ODI), and DTI parameters were assessed between T0 and T1. No significant difference in FA was found in treated roots, while MD (p = 0.0015), RD (p = 0.0032), and AD (p = 0.0221) were significantly altered. At untreated levels, all DTI parameters showed highly significant differences (p < 0.0001) between T0 and T1. In treated roots, FA values significantly increased in the intraforaminal segment(p = 0.0229), while MD(p = 0.0124), AD(p = 0.0128), and RD (p = 0.0143) values decreased in the pre-foraminal segment. In untreated roots, FA significantly increased in pre(p = 0.0039)and intraforaminal(p = 0.0003) segments, and MD, AD, and RD decreased in all segments (p < 0.0001). VAS (p < 0.0001) also decreased between T0 and T1. This pilot study aims to clarify the biomechanical impact of interspinous spacers through microstructural analysis of both treated and adjacent untreated nerve roots. To our knowledge, no studies have examined the short- to medium-term changes in DTI values of lumbar nerve roots before and after IPD placement, or compared changes between treated and untreated roots.

Exploring the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and aquaporin expression and biochemical composition content in degenerative intervertebral disc nucleus pulposus tissue: a clinical experimental study

OBJECTIVE

This study investigates the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and biochemical composition in degenerative intervertebral disc nucleus pulposus tissue, offering a potential reference for the clinical diagnosis and efficacy evaluation of intervertebral disc degeneration.

METHODS

Human lumbar intervertebral disc nucleus pulposus tissue samples were collected via full endoscopic minimally invasive surgery. DTI was employed to quantitatively measure fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in the degenerative nucleus pulposus, examining the relationship between Pfirrmann grading and these DTI parameters. Western blotting was used to detect the expression levels of aquaporin 1 (AQP1) and aquaporin 3 (AQP3) in the degenerative tissue. The glycosaminoglycan (GAG) content was quantified using the dimethylmethylene blue (DMMB) colorimetric assay, and collagen content was assessed with the Sircol soluble collagen assay kit. The relationship between Pfirrmann grading and biochemical composition was also analyzed. Finally, correlation analysis was performed between the FA and ADC values from the human nucleus pulposus tissue and their GAG and collagen contents.

RESULTS

A total of 39 patients (19 males, 20 females) with lumbar disc herniation (LDH), averaging 54.41 years of age, were included. As the degree of Pfirrmann degeneration increased, FA values rose, while ADC values continuously declined. Concurrently, as degeneration progressed, expression of AQP1 and AQP3 proteins decreased, GAG content significantly diminished, and collagen content increased. FA values exhibited a moderate negative correlation with GAG content (r = -0.5974, P < 0.0001) and a strong positive correlation with collagen content (r = 0.8694, P < 0.0001). ADC values showed a moderate positive correlation with GAG content (r = 0.6873, P < 0.0001) and a strong negative correlation with collagen content (r = -0.8502, P < 0.0001).

CONCLUSION

The FA and ADC values derived from magnetic resonance DTI, along with the protein expression levels of AQPs, can reflect the severity of intervertebral disc degeneration to a certain extent. Additionally, the content of glycosaminoglycans and collagen in the nucleus pulposus of the intervertebral disc correlates with the FA and ADC values of the DTI parameters. Therefore, magnetic resonance DTI quantitative imaging provides a means to assess the biochemical composition changes within the intervertebral discs, offering valuable insights for the clinical diagnosis and evaluation of therapeutic efficacy in intervertebral disc degenerative diseases.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2000041151, Registered on 19 December, 2020, https://www.chictr.org.cn/showproj.html?proj=206119 .

Feasibility study for evaluating cervical intervertebral disc degeneration using axial diffusion tensor imaging

BACKGROUND

Intervertebral disc (IVD) degeneration is the main cause of neck pain. Although conventional magnetic resonance imaging can detect morphological changes in intervertebral disc degeneration, it cannot provide accurate and objective evaluations. Magnetic resonance diffusion tensor imaging (DTI) reflects the microstructural changes in tissues by describing the diffusion of water molecules. It was initially applied to the evaluation of lumbar disc degeneration; however, no study has used DTI to evaluate cervical disc degeneration.

OBJECTIVE

To conduct a prospective study to evaluate the efficacy and feasibility of DTI in quantifying cervical disc degeneration by correlating the main parameters of axial DTI of intervertebral discs, namely fractional anisotropy (FA) and mean diffusivity (MD) values, using the Pfirrmann grade.

METHODS

The cervical discs of 30 symptomatic volunteers with neck pain and 20 asymptomatic volunteers were assessed using a 3.0 T magnetic resonance scanner. We evaluated intervertebral discs from C3/4 to C6/7 in each volunteer. The Pfirrmann grades, FA value, and MD value on the conventional magnetic resonance imaging were evaluated. The Kruskal-Wallis test and Wilcoxon rank-sum test were used to compare the FA and MD values of subjects with different degeneration levels.

RESULTS

Statistical analysis showed that the FA value of the nucleus pulposus in patients group was significantly higher than that in the asymptomatic volunteers, and the MD value of the nucleus pulposus was significantly lower than that in the asymptomatic volunteers, and the difference was significant (P < 0.05). In the study group, with an increase in cervical intervertebral disc grade, the FA value of the nucleus pulposus also showed a gradual upward trend, and this difference was significant (P < 0.05). The MD value of the nucleus pulposus showed a gradual downward trend, except between grades I and II, which indicates that the axial FA value can better show the early pathological changes of the cervical intervertebral disc.

CONCLUSIONS

The FA and MD values of the cervical intervertebral disc can quantitatively evaluate the degree of degeneration of the cervical intervertebral disc; axial DTI imaging technology can provide a good theoretical basis for the imaging diagnosis of cervical intervertebral disc degeneration and has important clinical application value.

Stepwise reduction of bony density in patients induces a higher risk of annular tears by deteriorating the local biomechanical environment

BACKGROUND CONTEXT

The relationship between osteoporosis and intervertebral disc degeneration (IDD) remains unclear. Considering that annular tear is the primary phenotype of IDD in the lumbar spine, the deteriorating local biomechanical environment may be the main trigger for annular tears.

PURPOSE

To investigate whether poor bone mineral density (BMD) in the vertebral bodies may increase the risk of annular tears via the degradation of the local biomechanical environment.

STUDY DESIGN

This study was a retrospective investigation with relevant numerical mechanical simulations.

PATIENT SAMPLE

A total of 64 patients with low back pain (LBP) and the most severe IDD in the L4-L5 motion segment were enrolled.

OUTCOME MEASURES

Annulus integration status was assessed using diffusion tensor fibre tractography (DTT). Hounsfield unit (HU) values of adjacent vertebral bodies were employed to determine BMD. Numerical simulations were conducted to compute stress values in the annulus of models with different BMDs and body positions.

METHODS

The clinical data of the 64 patients with low back pain were collected retrospectively. The BMD of the vertebral bodies was measured using the HU values, and the annulus integration status was determined according to DTT. The data of the patients with and without annular tears were compared, and regression analysis was used to identify the independent risk factors for annular tears. Furthermore, finite element models of the L4-L5 motion segment were constructed and validated, followed by estimating the maximum stress on the post and postlateral interfaces between the superior and inferior bony endplates (BEPs) and the annulus.

RESULTS

Patients with lower HU values in their vertebral bodies had significantly higher incidence rates of annular tears, with decreased HU values being an independent risk factor for annular tears. Moreover, increased stress on the BEP-annulus interfaces was associated with a stepwise reduction of bony density (ie, elastic modulus) in the numerical models.

CONCLUSIONS

The stepwise reduction of bony density in patients results in a higher risk of annular tears by deteriorating the local biomechanical environment. Thus, osteoporosis should be considered to be a potential risk factor for IDD biomechanically.

IVD fibrosis and disc collapse comprehensively aggravate vertebral body disuse osteoporosis and zygapophyseal joint osteoarthritis by posteriorly shifting the load transmission pattern

BACKGROUND

Disuse is a typical phenotype of osteoporosis, but the underlying mechanism has yet to be identified in elderly patients. Disc collapse and intervertebral disc (IVD) fibrosis are two main pathological changes in IVD degeneration (IDD) progression, given that these changes affect load transmission patterns, which may lead to disuse osteoporosis of vertebral bodies and zygapophyseal joint (ZJ) osteoarthritis (ZJOA) biomechanically.

METHODS

Clinical data from 59 patients were collected retrospectively. Patient vertebral bony density, ZJOA grade, and disc collapse status were judged via CT. The IVD fibrosis grade was determined based on the FA measurements. Regression analyses identified potential independent risk factors for osteoporosis and ZJOA. L4-L5 numerical models with and without disc collapse and IVD fibrosis were constructed; stress distributions on the bony endplate (BEP) and zygapophyseal joint (ZJ) cartilages were computed in models with and without disc collapse and IVD fibrosis.

RESULTS

A significantly lower disc height ratio and significantly greater FA were recorded in patients with ZJOA. A significant correlation was observed between lower HU values and two parameters related to IDD progression. These factors were also proven to be independent risk factors for both osteoporosis and ZJOA. Correspondingly, compared to the intact model without IDD. Lower stress on vertebral bodies and greater stress on ZJOA can be simultaneously recorded in models of disc collapse and IVD fibrosis.

CONCLUSIONS

IVD fibrosis and disc collapse simultaneously aggravate vertebral body disuse osteoporosis and ZJOA by posteriorly shifting the load transmission pattern.

Novel Magnetic Resonance Imaging Tools for the Diagnosis of Degenerative Disc Disease: A Narrative Review

Low back pain (LBP) is one of the leading causes of disability worldwide, with a significant socioeconomic burden on healthcare systems. It is mainly caused by degenerative disc disease (DDD), a progressive, chronic, and age-related process. With its capacity to accurately characterize intervertebral disc (IVD) and spinal morphology, magnetic resonance imaging (MRI) has been established as one of the most valuable tools in diagnosing DDD. However, existing technology cannot detect subtle changes in IVD tissue composition and cell metabolism. In this review, we summarized the state of the art regarding innovative quantitative MRI modalities that have shown the capacity to discriminate and quantify changes in matrix composition and integrity, as well as biomechanical changes in the early stages of DDD. Validation and implementation of this new technology in the clinical setting will allow for an early diagnosis of DDD and ideally guide conservative and regenerative treatments that may prevent the progression of the degenerative process rather than intervene at the latest stages of the disease.