The effects of axial loading on the morphometric and T(2) characteristics of lumbar discs in relation to disc degeneration

Different Load-Induced Alterations in Intervertebral Discs Between Low Back Pain Patients and Controls: A T2-map Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

Investigate load-induced effects in lumbar intervertebral discs (IVDs) and differences between low back pain (LBP) patients and controls.

SUMMARY OF BACKGROUND DATA

T2-map values, obtained from quantitative MRI sequences, reflect IVD tissue composition and integrity. Feasibility studies with T2-mapping indicate different load-induced effects in entire IVDs and posterior IVD parts between LBP patients and controls. Larger studies are required to confirm these findings and increase the understanding of specific characteristics distinguishing IVD changes in LBP patients compared with controls.

MATERIALS AND METHODS

Lumbar IVDs of 178 patients (mean age: 43.8 yr; range: 20-60 yr) with >3 months of LBP and 74 controls (mean age: 40.3 yr; range: 20-60 yr) were imaged with T2-map sequence in a 3T scanner in supine position without axial load, immediately followed by a repeated examination, using the same sequence, with axial load. On both examinations, mean T2-map values were obtained from entire IVDs and from central/posterior IVD parts on the three midsagittal slices in 855 patient IVDs and 366 control IVDs. Load-induced effect was compared with Fold-change ratio and adjusted for IVD-degeneration grade.

RESULTS

Loading induced an increase in T2-map values in both patients and controls. Excluding most extreme values, the ranges varied between -15% and +35% in patients and -11% and +36% in controls (first to 99th percentile). Compared with controls, the T2-map value increase in patients was 2% smaller in entire IVDs (Fold-change: 0.98, P =0.031), and for central and posterior IVD parts 3% (Fold-change: 0.98, P =0.005), respectively, 2% (Fold-change: 0.9, P =0.015) smaller.

CONCLUSIONS

This quantitative study confirmed diverse load-induced behaviors between LBP patients and controls, suggesting deviant biomechanical characteristics between IVDs in patients and controls not only attributed to the global grade of degeneration. These findings are an important step in the continuous work of identifying specific IVD phenotypes for LBP patients.

LEVEL OF EVIDENCE

Level II.

[Effectiveness of spinal traction in degenerative spine diseases. (A literature review)]

Back pain is one of the most urgent healthcare problems in many countries of the world. The high prevalence of the disease among persons of working age, the high disability indices and the high economic losses determine the relevance of this problem and its epidemiological and socio-economic significance.

OBJECTIVE

To analyze sources of scientific and technical literature and study materials of meta-analyses, systematic reviews on the issues of evaluation of the spinal traction effectiveness (dry and underwater, horizontal and vertical) in the treatment of patients with degenerative spine diseases.

MATERIAL AND METHODS

An analysis of 67 sources, including 54 periodical articles, 5 meta-analyses and 8 systematic reviews was conducted. The search depth was 20 years.

RESULTS

The ability of the spinal traction method to influence on the pain intensity, functional state, general improvement or return to work in patients with degenerative spine diseases has been identified. There has been a statistically significant regression of lumbar and radicular pain under the influence of «dry» horizontal tractions of the spine (13389 patients with degenerative spine diseases received them), including in combination with physiotherapy (vibration, impulse currents, laser therapy), and there has been an improvement in the motor function of the spine, a decrease in the disability rate in patients with herniated disks. These results were also obvious in short-term observation (up to 3 months after intervention). Underwater traction (5533 patients received it) had a positive impact on pain syndrome at rest and during activity, increased the activity of patients. All registered effects were related to short-term effect for up to 3 months after the intervention.

CONCLUSION

The evidence, based on the materials of meta-analyses and systematic reviews of medium and low quality, that «dry» and underwater spinal traction can be considered as a therapeutic tool for short-term (within 3 months) reducing pain and disability in patients with lumbar pain and lumbar radiculopathy, is presented.

Use of machine learning to select texture features in investigating the effects of axial loading on T2-maps from magnetic resonance imaging of the lumbar discs

BACKGROUND

Recent advances in texture analysis and machine learning offer new opportunities to improve the application of imaging to intervertebral disc biomechanics. This study employed texture analysis and machine learning on MRIs to investigate the lumbar disc's response to loading.

METHODS

Thirty-five volunteers (30 (SD 11) yrs.) with and without chronic back pain spent 20 min lying in a relaxed unloaded supine position, followed by 20 min loaded in compression, and then 20 min with traction applied. T₂-weighted MR images were acquired during the last 5 min of each loading condition. Custom image analysis software was used to segment discs from adjacent tissues semi-automatically and segment each disc into the nucleus, anterior and posterior annulus automatically. A grey-level, co-occurrence matrix with one to four pixels offset in four directions (0°, 45°, 90° and 135°) was then constructed (320 feature/tissue). The Random Forest Algorithm was used to select the most promising classifiers. Linear mixed-effect models and Cohen's d compared loading conditions.

FINDINGS

All statistically significant differences (p < 0.001) were observed in the nucleus and posterior annulus in the 135° offset direction at the L4-5 level between lumbar compression and traction. Correlation (P_2-Offset, P_4-Offset) and information measure of correlation 1 (P_3-Offset, P_4-Offset) detected significant changes in the nucleus. Statistically significant changes were also observed for homogeneity (P_2-Offset, P_3-Offset), contrast (P_2-Offset), and difference variance (P_4-Offset) of the posterior annulus.

INTERPRETATION

MRI textural features may have the potential of identifying the disc's response to loading, particularly in the nucleus and posterior annulus, which appear most sensitive to loading.

LEVEL OF EVIDENCE

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.