Posterior disk displacement: morphologic assessment and measurement reliability-lumbar spine

A method for quantitative measurement of lumbar intervertebral disc structures: an intra- and inter-rater agreement and reliability study

Background

There is a shortage of agreement studies relevant for measuring changes over time in lumbar intervertebral disc structures. The objectives of this study were: 1) to develop a method for measurement of intervertebral disc height, anterior and posterior disc material and dural sac diameter using MRI, 2) to evaluate intra- and inter-rater agreement and reliability for the measurements included, and 3) to identify factors compromising agreement.

Methods

Measurements were performed on MRIs from 16 people with and 16 without lumbar disc herniation, purposefully chosen to represent all possible disc contours among participants in a general population study cohort. Using the new method, MRIs were measured twice by one rater and once by a second rater. Agreement on the sagittal start- and end-slice was evaluated using weighted Kappa. Length and volume measurements were conducted on available slices between intervertebral foramens, and cross-sectional areas (CSA) were calculated from length measurements and slice thickness. Results were reported as Bland and Altman’s limits of agreement (LOA) and intraclass correlation coefficients (ICC).

Results

Weighted Kappa (K_w (95% CI)) for start- and end-slice were: intra-: 0.82(0.60;0.97) & 0.71(0.43;0.93); inter-rater: 0.56(0.29;0.78) & 0.60(0.35;0.81). For length measurements, LOA ranged from [−1.0;1.0] mm to [−2.0;2.3] mm for intra-; and from [−1.1; 1.4] mm to [−2.6;2.0] mm for inter-rater. For volume measurements, LOA ranged from [−293;199] mm³ to [−582;382] mm³ for intra-, and from [−17;801] mm³ to [−450;713] mm³ for inter-rater. For CSAs, LOA ranged between [−21.3; 18.8] mm² and [−31.2; 43.7] mm² for intra-, and between [−10.8; 16.4] mm² and [−64.6; 27.1] mm² for inter-rater. In general, LOA as a proportion of mean values gradually decreased with increasing size of the measured structures. Agreement was compromised by difficulties in identifying the vertebral corners, the anterior and posterior boundaries of the intervertebral disc and the dural sac posterior boundary. With two exceptions, ICCs were above 0.81.

Conclusions

Length measurements and calculated CSAs of disc morphology and dural sac diameter from MRIs showed acceptable intra- and inter-rater agreement and reliability. However, caution should be taken when measuring very small structures and defining anatomical landmarks.

Potential of magnetic resonance imaging findings to refine case definition for mechanical low back pain in epidemiological studies: a systematic review

STUDY DESIGN

systematic review and meta-analysis.

OBJECTIVE

to assess how confidently low back pain (LBP) can be attributed to abnormalities on magnetic resonance imaging (MRI), and thereby explore the potential value of MRI abnormalities in refining case definition for mechanical LBP in epidemiological research.

SUMMARY OF BACKGROUND DATA

most epidemiological studies of mechanical LBP have defined cases only by reported symptoms, but it is possible that the potency of causes differs depending on whether there is demonstrable underlying spinal pathology.

METHODS

we reviewed the published data on MRI abnormalities, looking for data on the repeatability of their assessment, their prevalence in people free from LBP, and their association with LBP. Where data were sufficient, we calculated a summary estimate of prevalence in people without LBP and a meta-estimate of the odds ratio for the association with LBP. A formula was then applied to estimate the corresponding prevalence rate ratio, assuming 3 possible prevalence rates for LBP in the general population.

RESULTS

data were most extensive for disc protrusion, nerve root displacement or compression, disc degeneration, and high intensity zone, all of which could be assessed repeatedly. All were associated with LBP, meta-estimates of odds ratios ranging from 2.3 (nerve root displacement or compression) to 3.6 (disc protrusion). However, even for disc protrusion, estimates of the corresponding prevalence rate ratios were mostly less than 2.

CONCLUSION

MRI findings of disc protrusion, nerve root displacement or compression, disc degeneration, and high intensity zone are all associated with LBP, but individually, none of these abnormalities provides a strong indication that LBP is attributable to underlying pathology. This limits their value in refining epidemiological case definitions for LBP.

Effect of long-term axial spinal unloading on vertebral body height in adult thoracolumbar spine

The human spine is influenced by mechanical loads. To our knowledge, this is the first study to assess the effect of long-term axial unloading on morphology of healthy vertebras in adults. The objective of this study is to quantify the effects of long-term relative axial unloading on thoracolumbar vertebral body height in adults. In this study, 218 vertebras on 200 plain lateral radiograms of patients with thoracolumbar vertebral body fracture, which underwent long segment instrumentation and fusion and had a relative axial unloading on five vertebrae of thoracolumbar spine were evaluated. Anterior vertebral body height (AVBH) and posterior vertebral body height (PVBH) proximal and distal to the fractured vertebrae were measured before and at least 1 year after the unloading operative procedures. AVBH of the first distal adjacent vertebrae and summative AVBHs of the first distal and proximal adjacent vertebras to the fractured vertebrae were significantly increased after 1 year of unloading, whereas the PVBH changes were not noticeable and the mean of cumulative height of two levels of proximal and distal adjacent vertebras to the fractured vertebrae did not show significant difference. Vertebral body height of lumbar was more influenced by unloading when compared with thoracic spine. Long-term relative axial unloading can affect the height of healthy vertebral bodies in adult spine.

Posterior disk displacement: morphologic assessment and measurement reliability--cervical spine

BACKGROUND

Magnetic resonance imaging (MRI) is often used to assess for disk displacement after manipulation, but limited information about the true incidence of iatrogenic herniations exists. Preliminary data must be obtained concerning the size of different types of displacement to further assess this relationship. The reliability of chiropractic radiologists in assessing disks, and a comparison of measuring devices should be evaluated.

OBJECTIVE

To identify average measurements for normal and displaced disks and to assess the reliability of measurements by chiropractic radiologists.

STUDY DESIGN

Intraobserver and interobserver reliability study assessing cervical disk displacement on MRI scans.

METHODS

Three evaluators assessed the disks on 106 MRI scans. Six categories were assessed and compared. Thirty-seven scans were reassessed for intraobserver comparisons. Interobserver and intraobserver variations and measurement-device correlations were determined.

RESULTS

Interexaminer measurement reliability for the 2 devices was 0.80 to 0.84. Intraexaminer reliability ranged from 0.58 to 0.94. Interexaminer and intraexaminer agreement for the presence of disk displacement was 86% (kappa = 0.69) and 78% to 85% (kappa = 0.50-0.67), respectively; for the presence of osteophytes, 92% (kappa = 0.54) and 86% to 95% (kappa = 0.60-0.80); and for the classification of disk displacements, 76% (kappa = 0.53) and 73% to 80% (kappa 0.44-0.61). Distinguishing between normal versus bulged disks demonstrated the greatest classification disagreement. Clear size differences between the types of disk displacement were noted. The ruler and digitizer correlation coefficient was 0.96.

CONCLUSIONS

Interexaminer and intraexaminer agreement were good to very good concerning measurements and fair to good concerning disk assessments. Different disk displacement types demonstrated obvious mean size differences. No significant mean difference in measurements between the ruler and the digitizer was noted.