A new quantitative measure of disc degeneration.

BACKGROUND CONTEXT: The ability to adequately measure a phenomenon is critical to studying and understanding it. Since 1957, a variety of subjective visual grading methods have been used to assess disc degeneration, but these have been limited by gross ordinal scales and imprecision, as well as suboptimal reliability. Conceptually sound, objective, precise measurements are needed to advance knowledge of disc degeneration and its causes, progression, and consequences. PURPOSE: This study aimed to investigate the reliability and validity of a new system ("SpIn" for spine insight) to quantitatively measure lumbar disc degeneration or pathology. STUDY DESIGN: This is a measurement study using cross-sectional and longitudinal data. PATIENT SAMPLE: The subjects were 108 men from 35 to 63 years of age at baseline. OUTCOME MEASURES: SpIn measures were validated using age, Pfirrmann grade, and other magnetic resonance imaging (MRI)-based disc and vertebral measurements associated with degeneration. METHODS: The lumbar spine was imaged using a 1.5 T Magnetom MRI scanner at baseline and a 1.5 T Avanto scanner at 15-year follow-up, forming two scanner-age groups. After the disc was manually traced on mid-disc axial MR images, image analysis software automatically measured distances, areas, and mean signal of regions of interest to calculate the new ratio-based disc degeneration measurements (SpIn). Repeated measurements were conducted on 30 subjects to estimate intra- and inter-rater reliability. Univariate methods and multiple regression modeling were used to compare associations of SpIn values and Pfirrmann grade, as a reference standard, with age and other degenerative and morphologic changes over follow-up. The MRI data used in the study were collected with support from the National Institutes of Health (NIH) National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and the Finnish Work Environment Fund. One author (TV) has a patent interest in SpIn. RESULTS: Intra-rater and inter-rater measurements for SpIn yielded correlation coefficients of at least 0.98. Associations with age were clearly weaker for Pfirrmann grade than for SpIn. The variance in age explained by axial SpIn values ranged from 15.0% to 23.4% (adjusted R2), depending on spinal level and scanner-age group, as compared with 5.9%-12.9% for Pfirrmann grade. Although both SpIn values and Pfirrmann grades were associated with familial aggregation, associations were generally higher with Pfirrmann grade. Baseline SpIn values and Pfirrmann grade were both associated with subsequent, structural degenerative changes in lumbar discs and vertebrae over the 15-year follow-up, but all associations were stronger with SpIn. CONCLUSIONS: SpIn provides a highly reliable, objective, continuous digital measurement of disc degeneration, which uses routinely acquired MRI and could benefit related research.

Cranio-caudal asymmetries in trabecular architecture reflect vertebral fracture patterns.

Clinically, vertebral fractures often occur in the upper lumbar spine and involve the superior endplate of a vertebra (which is immediately caudal to a disc). Knowledge that the cranial endplate of a disc is thicker and has greater bone mineral density (BMD) than the corresponding caudal endplate helps to explain this phenomenon. In this study, we investigated structural differences in vertebral trabeculae on either side of a lumbar disc to provide further insight into vertebral fracture risk. As the focus is trabecular difference within a spinal motion segment, we define cranial and caudal vertebral trabeculae relative to the disc. Ninety-two spinal motion segments from 46 cadaveric lumbar spines (males, mean age 50years, range 21-63years) were studied. Disc narrowing on radiography and spread of barium sulfate (BaSO4) on discography were measured to indicate disc degeneration. Micro-computed tomography (µCT) images were obtained at a resolution of 82µm for each vertebra and processed to include only vertebral trabeculae. Using image processing, the vertebral trabeculae were divided into superior and inferior halves, and then into central and peripheral regions which were approximately opposite to the disc pulposus and annulus, and further into anterior and posterior sub-regions. Microarchitecture measurements for each vertebral region were obtained to determine the differences between the cranial and caudal trabeculae (relative to disc) and their associations with age and disc degeneration within each spinal motion segment. Data from the upper (L1/2-L3/4) and lower (L4/5) lumbar segments were analyzed separately. In the upper lumbar region, the trabeculae cranial to a disc on average had 5.3% greater BMD and trabecular bone volume, 3.6% greater trabecular number, 9.7% greater connectivity density, and 3.7% less trabecular separation than the corresponding caudal trabeculae (P<0.05 for all). Similar trends were observed in peripheral, anterior and posterior regions, but not in central region. No structural difference was observed in the trabeculae of L4/5 segment. Structural asymmetries of vertebral trabeculae were not associated with age, disc degeneration, or disc narrowing. Vertebral trabecular parameters cranial to the disc were greater than caudally in the upper but not in the lower lumbar region. Findings further explain why vertebral fractures are more common in the upper lumbar region and more frequently involve the endplate caudal to a disc.

Association study of MMP8 gene in osteoarthritis.

OBJECTIVES: Osteoarthritis (OA) is a joint disease common in the elderly. There is a prior functional evidence for different matrix metalloproteinases (MMPs), such as MMP8 and MMP9, having a role in the breakdown of cartilage extracellular matrix in OA. Thus, we analyzed whether the common genetic variants of MMP8 and MMP9 contribute to the risk of OA. MATERIALS AND METHODS: In total, 13 common tagging single-nucleotide polymorphisms (SNPs) were studied in a discovery knee OA cohort of 185 cases and 895 controls. For validation, two knee OA replication cohorts and two hand OA replication cohorts were studied (altogether 1369 OA cases, 4445 controls in the five cohorts). The χ(2) test for individual study cohorts and Cochran-Mantel-Haenszel test for combined meta-analysis were calculated using Plink. RESULTS: The rs1940475 SNP in MMP8 showed suggestive association in the discovery cohort (OR = 0.721, 95% CI 0.575-0.906; p = 0.005). Other knee and hand OA replication study cohorts showed similar trend for the predisposing allele without reaching statistical significance in independent replication cohorts nor in their meta-analysis (p > 0.05). Meta-analysis of all five hand and knee OA study cohorts yielded a p-value of 0.027 (OR = 0.904, 95% CI 0.826-0.989). CONCLUSIONS: Initial analysis of the MMP8 gene showed suggestive association between rs1940475 and knee OA, but the finding did not replicate in other study cohorts, even though the trend for predisposing allele was similar in all five cohorts. MMP-8 is a good biological candidate for OA, but our study did not find common variants with significant association in the gene.

The distribution of bone mass in the lumbar vertebrae: are we measuring the right target?

BACKGROUND CONTEXT: The ideal target of bone mineral density (BMD) measurements of the spine is the trabecula-rich vertebral body. Yet, spine BMD measurements routinely obtained with dual-energy X-ray absorptiometry also include the posterior elements of the vertebra, which are mainly cortical bone and insensitive to bone loss. PURPOSE: We compared the bone mass of the vertebral body and posterior elements to determine the contributions of vertebral components to vertebral BMD measurements. STUDY DESIGN: A micro-computed tomography study of lumbar vertebral bone. METHODS: From a spine archive, 144 cadaveric lumbar vertebrae (L1-L5) from 48 male human spines (mean age, 50 years) were scanned in air using micro-computed tomography to measure bone volume, bone mineral content (BMC) and BMD of the vertebral body, posterior elements, and entire vertebra. The contributions of the vertebral components to the total vertebral BMC and volume were compared, and the correlations between the BMC and BMD of the vertebrae and their components were examined. RESULTS: Overall, the vertebral body contributed about one-third of the total vertebral BMC and two-thirds of the total vertebral volume, and the posterior elements contributed the remainder. The vertebral body BMC and BMD were poorly correlated to those of the posterior elements (r=0.39 for BMC and r=0.34 for BMD, p<.0001) and moderately correlated to the whole vertebra (r=0.77 and 0.75, respectively, p<.0001). The BMC and BMD of the posterior elements and whole vertebra were more strongly correlated (r=0.89 and 0.84, respectively, p<.0001). CONCLUSIONS: The posterior elements are the primary contributor to vertebral BMC and BMD measurements. Dual-energy X-ray absorptiometry spine BMD measurements are likely to be more representative of the posterior elements than the targeted vertebral body. The findings elucidate the extent of the limitation of dual-energy X-ray absorptiometry spine BMD measurements.

Lumbar spinal stenosis is a highly genetic condition partly mediated by disc degeneration.

Objective. Lumbar spinal stenosis is one of the most commonly diagnosed spinal disorders in older adults. Although the pathophysiology of the clinical syndrome is not well understood, a narrow central canal or intervertebral foramen is an essential or defining feature. The aim of the present study was to estimate the magnitude of genetic versus environmental influences on central lumbar spinal stenosis and to investigate disc degeneration and stature or bone development as possible genetic pathways.Methods. A classic twin study with multivariate analyses considering lumbar level and other covariates was conducted. The study sample comprised 598 male twins (147 monozygotic and 152 dizygotic pairs), 35-70 years of age, from the population-based Finnish Twin Cohort. The primary phenotypes were central lumbar stenosis as assessed qualitatively on magnetic resonance imaging (MRI) and quantitatively measured dural sac cross-sectional area. Additional phenotypes (to examine possible genetic pathways) included disc bulging and standing height, as an indicator of overall skeletal size or development.Results. The heritability estimate (h²) for qualitatively assessed central lumbar spinal stenosis on MRI was 66.9% (95% confidence interval [95% CI] 56.8,74.5). The broad-sense heritability estimate for dural sac cross-sectional area was 81.2% (95% CI 74.5, 86.1),with a similar magnitude of genetic influences across lumbar levels (h²=72.4­75.6). The additive genetic correlation of quantitatively assessed stenosis and disc bulging was extremely high. There was no indication of shared genetic influences between stenosis and stature.Conclusion. Central lumbar spinal stenosis and associated dural sac dimensions are highly genetic, and disc degeneration (bulging) appears to be one pathway through which genes influence spinal stenosis.

Aging changes in lumbar discs and vertebrae and their interaction: a 15-year follow-up study.

BACKGROUND CONTEXT: Many studies have focused on either the intervertebral disc as a culprit in back pain problems, or the vertebral body, but very few studies have examined both structures and their relationship. PURPOSE: To measure the concordant changes in morphology of the discs and vertebrae during 5-, 10-, and 15-year follow-ups. STUDY DESIGN: Longitudinal study. PATIENT SAMPLE: Among a general population sample of 232 men that had been scanned in 1992-1993, 105 men were reexamined in 1997-1998 and 2007-2008. Mean age at the 15-year follow-up was 63 years. A confirmatory sample with 10 years follow-up was also included. METHODS: Scanners (1.5 Tesla) with surface coils were used at baseline and follow-up. Image analyzing software was used to measure distances and areas of interest of midsagittal and midaxial spine images. RESULTS: The disc heights decreased at 5 years by 3.4% (0.4 mm) and 3.3% (0.4 mm) and at 15 years by 8.7% (1.0 mm) and 11.3% (1.3 mm) in the upper and lower discs, respectively (p<.001). Although not clear after 5 years, vertebra heights increased in mean by 3.1% (0.8 mm) in the upper lumbar levels and by 4.7% (1.1 mm) in the lower vertebrae after 15 years (p<.001). Vertebra height increases were associated with disc narrowing (p=.001). The mean annual shortening of the lumbar spine L1-S1 block was 0.13 mm/y, which was in line with the mean standing height that decreased little (174.7 cm at baseline and 174.4 cm at the follow-up). CONCLUSIONS: Discs and vertebrae degenerate or remodel in concert: decreases in disc height appear to be compensated, in part, by accompanying increases in adjacent vertebra heights. The mechanism behind this novel finding and its implications require further study.

Paraspinal muscle morphology and composition: a 15-yr longitudinal magnetic resonance imaging study.

PURPOSE: The purposes of this study were to define the natural progression of age-related changes of the lumbar paraspinal muscles during adulthood and to investigate the influence of lifestyle and individual factors (e.g., physical activity levels at work and leisure, body mass index, and low back pain [LBP]). METHODS: This population-based longitudinal study included a sample of 99 adult male twins. Data were collected through a structured interview, physical examination, and magnetic resonance imaging. Measurements of the lumbar multifidus and erector spinae muscles were obtained from T2-weighted axial images at L3-L4 and L5-S1 at baseline and 15-yr follow-up. Muscle cross-sectional area (CSA), functional CSA (FCSA) (fat-free mass), and FCSA/CSA (composition) as well as CSA and FCSA asymmetry and FCSA/CSA side-to-side differences were measured. RESULTS: Subjects' mean ± SD age was 47.3 ± 7.4 yr at baseline and 62.3 ± 8.0 yr at follow-up. During the 15-yr period, both muscles exhibited a decrease in CSA and FCSA and an increase in fatty infiltration and side-to-side differences in size and composition at both spinal levels. Both muscles displayed greater changes at L5-S1 than L3-L4. Age and BMI were found to be significantly associated with the degree of paraspinal muscle changes over time. However, there was no association between the change in paraspinal muscle size, composition, or asymmetry with the level of physical demands at work or leisure or LBP history. CONCLUSIONS: The present longitudinal study suggests that over adulthood, the multifidus and erector spinae undergo similar morphological changes. Moreover, our findings suggest that the long-term progression of lumbar paraspinal muscle changes evaluated through magnetic resonance imaging are not associated with the range of physical demand levels as were typical of Finnish men or LBP history.

Regional variations in trabecular architecture of the lumbar vertebra: associations with age, disc degeneration and disc space narrowing.

Previous studies suggest that age and disc degeneration are associated with variations in vertebral trabecular architecture. In particular, disc space narrowing, a severe form of disc degeneration, may predispose the anterior portion of a vertebra to fracture. We studied 150 lumbar vertebrae and 209 intervertebral discs from 48 cadaveric lumbar spines of middle-aged men to investigate regional trabecular differences in relation to age, disc degeneration and disc narrowing. The degrees of disc degeneration and narrowing were evaluated using radiography and discography. The vertebrae were dried and scanned on a µCT system. The µCT images of each vertebral body were processed to include only vertebral trabeculae, which were first divided into superior and inferior regions, and further into central and peripheral regions, and then anterior and posterior regions. Structural analyses were performed to obtain trabecular microarchitecture measurements for each vertebral region. On average, the peripheral region had 12-15% greater trabecular bone volume fraction and trabecular thickness than the central region (p<0.01). Greater age was associated with better trabecular structure in the peripheral region relative to the central region. Moderate and severe disc degeneration were associated with higher trabecular thickness in the peripheral region of the vertebral trabeculae (p<0.05). The anterior region was of lower bone quality than the posterior region, which was not associated with age. Slight to moderate narrowing was associated with greater trabecular bone volume fraction in the anterior region of the inferior vertebra (p<0.05). Similarly, greater disc narrowing was associated with higher trabecular thickness in the anterior region (p<0.05). Better architecture of peripheral trabeculae relative to central trabeculae was associated with both age and disc degeneration. In contrast to the previous view that disc narrowing stress-shields the anterior vertebra, disc narrowing tended to associate with better trabecular architecture in the anterior region, as opposed to the posterior region.

Morphometrics and lesions of vertebral end plates are associated with lumbar disc degeneration: evidence from cadaveric spines.

BACKGROUND: Prior studies have suggested that vertebral end plate morphometrics and lesions may play a role in disc degeneration. However, most prior end plate studies have been based on radiographic images, and findings of associations between end plate morphometrics (measurements of size and shape) and disc degeneration remain controversial. The present study investigated the prevalence of vertebral end plate lesions and determined end plate morphometrics through direct measurements of cadaveric spines, and it examined the association of these factors with disc degeneration. METHODS: We studied 600 vertebral end plates and 313 intervertebral discs from the cadaveric lumbosacral spines of seventy-six men (mean age, fifty-one years). Discography was performed to evaluate disc degeneration as indicated by disruption of the anulus fibrosus. The shape of the vertebral end plate and the presence of any lesions were visually evaluated. Lesions were rated as absent, small to moderate, or large. In addition, each end plate was digitized to quantify its area, circularity, and concavity. The association of end plate morphometrics and lesions with disc degeneration was examined. RESULTS: Vertebral end plate lesions were found in 72% (fifty-five) of the seventy-six lumbar spines and in 32.8% (197) of the 600 end plates. The presence of end plate lesions was associated with disc degeneration, with larger lesions being associated with more severe disc degeneration (odds ratio, 2.31 for small to moderate lesions [p < 0.01] and 3.54 for large lesions [p < 0.001]). Greater end plate area was also associated with more severe disc degeneration (odds ratio, 1.2 per cm2 [p < 0.05]). CONCLUSIONS: Vertebral end plate lesions were common and were associated with adjacent disc degeneration, with greater lesion size being associated with more severe disc degeneration. End plate morphometrics, particularly greater end plate size, may also play a role in the pathogenesis of disc degeneration.

A morphological study of lumbar vertebral endplates: radiographic, visual and digital measurements.

PURPOSE: Clinical observations suggest that endplate shape and size are related to complications of disc arthroplasty surgery. Yet, the morphology of the vertebral endplate has not been well defined. This study was conducted to characterize the morphology of lumbar vertebral endplates and to quantify their morphometrics using radiographic, visual and digital measures. METHODS: A total of 591 vertebral endplates from 76 lumbosacral spines of men were studied (mean age 51.3 years). The shape of the vertebral endplates was classified as concave, flat and irregular, and was evaluated from both radiographs and cadaveric samples. Each endplate was further digitized using a laser scanner to quantify diameters, surface area and concavity for the whole endplate and its components (central endplate and epiphyseal rim). The morphological characteristics and morphometrics of the vertebral endplates were depicted. RESULTS: In both radiographic and visual assessments, more cranial endplates (relative to the disc) were concave and more caudal endplates were flat at all disc levels (p < 0.001). On average, the mean concavity depth was 1.5 mm for the cranial endplate and 0.7 mm for the caudal endplate. From L1/2 down to L5/S1 discs, the vertebral endplate gradually changed into a more oval shape. The central endplate was approximately 70% of the diameter of the whole endplate and the width of the epiphyseal rim varied from 3 to 7 mm. CONCLUSIONS: There is marked morphological asymmetry between the two adjacent endplates of a lumbar intervertebral disc: the cranial endplate is more concave than the caudal endplate. The size and shape of the vertebral endplate also vary considerably between the upper and lower lumbar regions.

ISSLS prize winner: Lumbar vertebral endplate lesions: associations with disc degeneration and back pain history.

STUDY DESIGN: An autopsy study. OBJECTIVE: To investigate associations between various types of lumbar endplate lesions, disc degeneration (DD), and back pain history. SUMMARY OF BACKGROUND DATA: The well-innervated vertebral endplate has been suspected as a source of back pain. Previously, we observed 4 types of lumbar endplate lesions with distinct morphological characteristics. Their roles in DD and back pain remain unclear. METHODS: From a lumbar spine archive of 136 men (mean age, 52 yr), back pain, back injury, and occupation history data for 69 subjects and discography data for 443 discs from 109 subjects were available for study. Back pain history was categorized as none, occasional, or frequent. DD was judged from discography. Endplate lesions were classified as Schmorl's nodes, fracture, erosion, or calcification, and lesion size was rated as none, small, moderate, or large. Associations between endplate lesions and DD, back pain history, back injury, and occupation history were examined. RESULTS: Presence of endplate lesions was associated with frequent (odds ratio [OR] = 2.57) but not occasional back pain. However, large endplate lesions were associated with both occasional (OR = 8.68) and frequent (OR = 17.88) back pain. This association remained after further controlling for DD. Also, the presence of each type of endplate lesion was associated with adjacent DD (OR = 2.40-9.71), with larger lesions associated with more severe DD. Endplate erosion lesions were more strongly associated with adjacent DD than Schmorl's nodes. Although back injury history was associated with the presence of fracture and erosion lesions, heavy occupation was associated with the presence of Schmorl's nodes. CONCLUSION: Endplate lesions are associated with back pain as well as being closely associated with adjacent DD, with a clear dosage effect. Different types of endplate lesions seem to have different magnitudes of associations with DD. Lumbar endplate lesions may be an important key to better understand both DD and back pain.

Modic changes: prevalence, distribution patterns, and association with age in white men.

BACKGROUND CONTEXT: Suspected as a cause of back pain, Modic changes (MCs) have received increasing attention in spine research and care. Yet, epidemiologic knowledge of MCs based on the general population, which may provide an important clinical reference, is limited. PURPOSE: To investigate the prevalence and distribution patterns of MCs in the lumbosacral spine and their associations with age in a large population-based sample of men. STUDY DESIGN: An epidemiologic investigation of lumbar magnetic resonance images (MRIs). PATIENT SAMPLE: This study was based on the Twin Spine Study database, comprising a sample of male twins shown to be largely representative of the base Finnish population. Lumbar spine MRIs (1.5 Tesla Magnetom; Siemens AG, Erlangen, Germany) of 561 subjects (mean age, 49.8 years; range, 35-70 years) were included in the present study. METHODS: For each spine, all 11 end plates (L1-S1) in the lumbar region were evaluated using both T1- and T2-weighted images to identify MCs, which were classified into Type 1, 2, 3, and mixed types. Furthermore, the number and location of MCs were recorded, as well as the anteroposterior (AP) and transverse sizes, to explore the prevalence and distribution pattern of MCs in the lumbar region and associations with age. RESULTS: Modic changes were identified in 55.6% (312) of individuals and 13.5% (830) of end plates studied. Among these MCs, 64.2% (533) were Type 2, 16.0% (133) were Type 1, 18.1% (150) were Mixed Type 1/2, and the remaining 1.6% (13) were noted as Type 3 or Mixed Type 2/3. Modic changes were more common in the lower (74.5%) than in the upper lumbar region (25.5%), and 77.9% (642) of MCs presented in pairs at opposing end plates of a disc. Moreover, the specific type of MCs on opposing end plates was usually concordant. The presence of MCs in the lumbar region was associated with age (odds ratio=1.05-1.08 for each additional year of age, depending on type of MCs, p<.001). In addition, greater age was associated with a greater number of end plates affected and MCs of larger size (p<.001). CONCLUSIONS: Modic changes are common MRI findings in the lumbar spines of middle-aged white men, with Type 2 MCs predominating. Mainly present in the lower lumbar region, MCs tend to affect both end plates adjacent to a disc simultaneously, and they commonly involve the entire AP diameter of the vertebral end plate. The presence and size of MCs are clearly related to age, suggesting that aging or associated factors may play an essential role in the pathogenesis of MCs.

Lumbar vertebral endplate lesions: prevalence, classification, and association with age.

STUDY DESIGN: A cross-sectional autopsy study. OBJECTIVE: This study investigated the prevalence of endplate lesions, classified them on the basis of morphological features, and determined their distribution patterns through direct measurements of cadaveric spines as well as examining their associations with age. SUMMARY OF BACKGROUND DATA: Endplate lesions may play a role in disc degeneration and back pain; however, related research has been rare. While Schmorl's nodes have received some attention, other endplate pathologies have been largely ignored. A systematic study of endplate lesions is needed to reveal the types and prevalence of lesions present in the adult lumbar spine. METHODS: We studied 1148 vertebral endplates (L1-S1) from the cadaveric spines of 136 men (mean age, 52 yr). On the basis of morphological characteristics, 4 types of endplate lesions were identified, including Schmorl's nodes, fracture, erosion, and calcification. The lesion location, size, and involved endplate components were evaluated to depict their distribution patterns. The associations between endplate lesion findings and age were also examined. RESULTS: Endplate lesions were found in 45.6% of lumbar vertebral endplates. Schmorl's nodes were the most common and usually were small, located centrally, and most common in the upper lumbar region. Erosion and calcification lesions were relatively large and most common in the lower lumbar region. The presence of lesions on 1 endplate of the disc was associated with presence of lesions on the opposing endplate (odds ratio = 8.0, P < 0.001). Greater age was associated with the presence of each type of endplate lesion. CONCLUSION: Endplate lesions are common and tend to affect both adjacent endplates of a disc simultaneously. The distribution patterns of the various types of endplate lesions differ, suggesting that they may have different pathogenic origins. Age or associated factors may play an important role in the pathogenesis of endplate lesions.

Is greater lumbar vertebral BMD associated with more disk degeneration? A study using µCT and discography.

It is well documented that osteoarthritis is associated with greater BMD in peripheral extremities. Yet the relationship between vertebral BMD and disk degeneration (DD) remains controversial in the lumbar spine, which may be due largely to the inadequacies of BMD and DD measures. Aiming to clarify the association between vertebral BMD and adjacent DD, we studied 137 cadaveric lumbar vertebrae and 209 corresponding intervertebral disks from the spines of 48 white men aged 21 to 64 years. DD was evaluated using discography. The vertebrae were scanned using a micro-computed tomography (µCT) system to obtain volumetric BMD for the whole vertebra, the vertebral body, the vertebral body excluding osteophytes, and the vertebral body excluding osteophytes and endplates. A random effects model was used to examine the association between the different definitions of vertebral BMD and adjacent DD. No significant association was found between the BMD of the whole vertebra and adjacent DD. However, when the posterior elements were excluded, there was a significant association between greater vertebral body BMD and more severe degeneration in the disk cranial to the vertebra. This association remained after further excluding osteophytes and endplates from the vertebral body BMD measurements. Also, a trend of greater BMD of the vertebral body associated with more adjacent DD was evident. These results clarify the association between vertebral BMD and DD and specifically indicate that it is higher BMD of the vertebral body, not the entire vertebra, that is associated with more severe adjacent DD. This association may be obscured by the posterior elements and is not confounded by osteophytes and endplate sclerosis.

Quantitative measures of modic changes in lumbar spine magnetic resonance imaging: intra- and inter-rater reliability.

STUDY DESIGN: A measurement reliability study. OBJECTIVE: To develop quantitative measures for Modic changes (MCs) on magnetic resonance (MR) images and evaluate measurement reliability. SUMMARY OF BACKGROUND DATA: MCs have been studied for more than 20 years but the clinical significance remains controversial. Little effort has been made to improve the measurement of MCs. METHODS: The study was approved by the responsible institutional review board. On the basis of Modic classification, a series of quantitative dimension and signal intensity measures were developed for assessing MCs. Midsagittal T1- and T2-weighted MR images from 83 lumbar spines were then qualitatively and quantitatively assessed by two observers independently. Kappa and intraclass correlation coefficient (ICC) were used to examine intra- and inter-rater reliability. Pearson correlation coefficient was used to assess the relationships between the quantitative measurements of MCs. Mean absolute deviation (MAD) and Bland-Altman plots also were used to evaluate measurement errors and limits of agreement for selected measures. RESULTS: For Modic classification, intrarater agreement was excellent (κ = 0.88) and inter-rater agreement was substantial (κ = 0.79). Intrarater agreement also was excellent when obtaining dimension measurements (ICC = 0.82-0.96) from T1- or T2-weighted images and inter-rater agreement was slightly greater using T1-weighted images (ICC = 0.73-0.88) than T2-weighted images (ICC = 0.66-0.82). Signal intensity measurements on T2-weighted images were found to have almost perfect intra- and inter-rater reliability (ICC = 0.92-0.99). The correlation analysis demonstrated that the quantitative measures represent different constructs. The MAD and Bland-Altman Plots further confirmed the high reliability of the area ratio, MCs mean signal intensity and MCs total signal intensity measurements. CONCLUSION: Three quantitative measures are suggested to assess the severity of MCs, which provide reliable, precise measurements for research on the etiology, pathogenesis, and clinical relevance of MCs.