Factors Associated With Lumbar Intervertebral Disc Degeneration In The Elderly

IntroduceMRI is useful for evaluating degeneration of intervertebral disks; it is essential for both their diagnosis and their grading. Most classification systems for degenerative intervertebral disks focus on signal intensity and structural morphology of the nucleus pulposus on sagittal T2-weighted MR images because decreased signal intensity reflects decreased water and proteoglycan concentrations caused by degeneration. However, signal intensity cannot be measured in absolute terms because of the many arbitrary factors in signal detection and amplification.This may lead to interobserver bias,especially when observers classify relatively small changes in signal intensity as representative of early degeneration. MRI in the sagittal.plane may make it possible to assess different levels of intervertebral disks and adjacent structures such as endplates, vertebral bodies,and bone spurs at one time; It has been suggested that early degenerative disks may exist before there is loss of signal intensity seen on T2-weighted MR images .Because degenerative intervertebral disks have been suggested as a potential cause of lower back pain, development of a classification system that can detect degeneration at an earlier stage may help in understanding the relationship between degenerative disks and lower back pain.T2 is sensitive to water content and the arrangement of the collagen network structure and is also influenced by the dipolar interaction because of the anisotropic motion of water molecules in the collagen matrix .A high T2 for the nucleus pulposus has been shown in healthy intervertebral disks; T2 decreases with the decrease of water content associated with disk degeneration. In contrast, T2 for the annulus fibrosus is low in healthy intervertebral disks, and it increases with increased water content and loss of collagen anisotropy.As degeneration progresses, uniformity of T2 in both the nucleus pulposus and the annulus fibrosus will decrease and, finally, the distinction of signal intensity between the nucleus pulposus and the annulus fibrosus will be lost. Because changes in composition are observed early in intervertebral disk degeneration and progress as it advances, sagittal T2-weighted MR images can be an ideal quantitative marker of degeneration.With current clinical MR imaging techniques, changes in intervertebral disks due to degeneration or repair can be detected only when new morphologic features appear. To detect intervertebral changes that are not accompanied by a new morphologic feature, sagittal T2-weighted MR imaging methods have been developed. The current strategy used to quantify disk degeneration by MR is the use of morphologic criteria.Specific findings such as clefts in the annulus fibrosus, decreased signal intensity, and loss of height are used to stage degeneration. Such scales,which typically include 5 stages, fail to identify lesser degrees of progression or regression of degeneration in the disk. To evaluate new novel therapies for treatment of intervertebral disk degeneration such as gene therapy a more sensitive technique is required. A reliable continuous scale is needed to track the progression and regression of disk degeneration.One potential tool for studying disk degeneration is a T2-weighted MR imaging methods of the disk. The feasibility of detecting degeneration with T2 measurements has been demonstrated,with relatively long acquisitions and low field strengths.One of the aim of this study was to establish an MRI classification system for degenerative disks using sagittal T2-weighted MR images with a special focus on evaluating early degenerative intervertebral disks. and to measure the variation of T2 through the disk.Maturation of human intervertebral disks has been studied in anatomic specimens. Disks in the neonate have a translucent mucoid matrix that contains notochordal cells, whereas disks in the second decade of life have a semiopaque matrix that contains chondrocytes. Fiber content increases in the intervertebral disk during this period of life, especially in the most central region of the disk. MR imaging reveals changes in the intervertebral disk in the first 2 decades of life.The intervertebral disk in the neonate is characterized by high signal intensity in T2-weighted images except in the peripheral annulus fibrosus, which has a low signal intensity sharply demarcated from the region of higher signal intensity. In the adult, the disk has a less homogeneous region of high signal intensity that is less well differentiated from the surrounding outer annulus fibrosus. The adult disk has another feature not seen in the juvenile intervertebral disk. This feature is a region of higher fiber content, which in T2-weighted MR images is distinguished as a central lower signal intensity region (CLSIR), popularly called the "intranuclear cleft," despite the absence of a true cleft in histologic studies. Disks in young children typically conform to stage I, and those in young adults that lack evidence of degenerative change typically conform to stageⅡin the Priffmann classification on the basis of the appearance on MR images.The relative concentration of water has been used to measure the changes in the disk as a result of aging and degeneration.Disk water decreases with aging and degeneration. The effect of disk maturation on water content has not been characterized as thoroughly. On the basis of studies on intervertebral disks in cadavers, Coventry claimed that water content increased in the disk during the first 2 decades of life, though the exact water concentrations were not reported.An MR-based method for estimating water content in the intervertebral disk has been described and applied to the study of disk degeneration.In one more recent study, the T2 was measured in intervertebral disks in patients subjected to trauma. Other examples of the use of T2 relaxometry for studying the intervertebral disk include measuring changes in disk water due to diurnal variation and due to the effects of spinal loading. In these studies, spatial variation of T2 in the intervertebral disk has not generally been considered. Hypothetically the T2 relaxation of the disk varies among different regions within the disk as does signal intensity. Because the amorphous region in the intervertebral disk near the endplate has greater signal intensity than the "intranuclear cleft" region or the annulus fibrosus, T2 likely varies from one region to another.Furthermore,the T2 relaxation time of the disk may be characterized by combinations of slower and faster components. The effect of this variation on the T2 measurement as an index of disk integrity has, not to the best of our knowledge,been reported.The value of T2 measurements as a measure of disk degeneration deserves more study. Potentially, the T2 measurement may identify early disk degeneration before the loss of signal intensity is sufficiently conspicuous that the inspection of the image will detect it. [47jHypothetically, normal-appearing disks with lower than average T2 values are more likely to demonstrate degenerative changes over time than disks with average T2 values.PURPOSEPrimaly, to clarify these factors and lumbar disc degeneration (Lumbar intervertebral disc degeneration, IVDD) of the relationship; through the lumbar intervertebral disc degeneration-related factors:age, gender studies; secondly, to study T2 signal intensity of lumbar disc and lumbar disc degeneration occurs morphological relationship.STUDY PATIENT SAMPLEObservational studies 229 cases (51～80years) subjects, DD evaluated based on the signal intensity of MR T2-weighted midsagittal images of the lumbar spineMETHODSthe age and degree of disc degeneration was estimated by calculating the Spearman correlation analysis; the Mann-Whitney nonparametric test and ANOVA was used to correlate the different levels of disc degeneration disc level; lumbar disc T2 signal value and the relationship between classification using non-parametric correlation analysis; analysis of variance was used to test intervertebral disc signal value with different disc levels (L5-L1) of the different age groups; constitute ratio was assessed using chi-square test disc degeneration between men and womenRESULTSWith increasing age, degree of disc degeneration will increase accordingly;1.Constituent ratio of disc degeneration was no difference between men and women;2.Different age groups with different lumbar interverterbral disc levels (L1-L5) intervertebral disc signal values are not the same, and with age, lumbar interverterbral disc degeneration occurred gradually, thus decreasing the value of lumbar interverterbral disc signal and a corresponding increase in degenerative level;3.Difference was exsited in disc degeneration of different levels of lumbar interverterbral discs;4.Degree of interverterbral disc degeneration was negative correlation T2 signal intensty of interdiscCONCLUSIONSAging are associated with intervertebral disc degeneration Thus sex are not associated with intervertebral disc degeneration; intervertebral disc degenera-tion and T2 signal intensity was significantly negatively correlated.