Current understanding of lumbar disc degeneration

The effect of compressive loading rate on annulus fibrosus strength following endplate fracture

Intervertebral disc degeneration poses a considerable healthcare challenge, although the process is not well understood. Endplate fracture marks severe biomechanical compromise in a segment and may be correlated with degeneration of the disc. The purpose of this experiment was to investigate the relationship between endplate fracture velocity and damage to the annulus fibrosus. Following overnight-thawing, 27 frozen porcine cervical spines were dissected into motion segments (vertebra-disc-vertebra) and compressed until fracture at one of three loading rates (fast=15 mm/s, medium=1.5 mm/s, and slow=0.15 mm/s), or remained unfractured (control). Two annular samples were extracted and mechanically tested from each segment: 1) Bilayer samples underwent uniaxial tension to a stretch-ratio of 1.5; 2) Multilayer samples were delaminated with a 180° peel test configuration. All three rates of compression resulted in specimen fracture observed in the endplate and/or vertebra with varying degree of severity. Significant differences were detected in compressive strength and stiffness of motion segments when loaded at different rates of compression; interestingly these differences were not observed in the mechanical properties of the annulus fibrosus suggesting that at slow rates of loading, fracture of the endplate precedes destruction of the annulus fibrosus. In corroboration of these findings, gross and histological analysis reported no signs of annular disruption, strengthening assertions that annular damage did not occur.

The Influence of Axial Compression on the Cellular and Mechanical Function of Spinal Tissues; Emphasis on the Nucleus Pulposus and Annulus Fibrosus: A Review

In light of the correlation between chronic back pain and intervertebral disc (IVD) degeneration, this literature review seeks to illustrate the importance of the hydraulic response across the nucleus pulposus (NP)-annulus fibrosus (AF) interface, by synthesizing current information regarding injurious biomechanics of the spine, stemming from axial compression. Damage to vertebrae, endplates (EPs), the NP, and the AF, can all arise from axial compression, depending on the segment's posture, the manner in which it is loaded, and the physiological state of tissue. Therefore, this movement pattern was selected to illustrate the importance of the bracing effect of a pressurized NP on the AF, and how injuries interrupting support to the AF may contribute to IVD degeneration.

Assessing the correlation between the degree of disc degeneration on the Pfirrmann scale and the metabolites identified in HR-MAS NMR spectroscopy

OBJECTIVE

The objective of this study is to assess the correlation between the degree of degeneration of lumbar discs according to the Pfirrmann classification system and the concentrations of metabolites determined by means of 1H high-resolution magic angle spinning nuclear magnetic resonance (1H HR MAS NMR) spectroscopy.

MATERIALS AND METHODS

Twenty-six human intervertebral lumbar discs that were operated on due to degenerative disease were analyzed. Routine preoperative 1.5T, T2-weighed magnetic resonance (MR) images were used to classify the cases according to the Pfirrmann classification system. In all the cases, during microdiscectomy, the fragments of the annulus fibrosus and nucleus pulposus were harvested and their metabolic profile was examined by means of 1H HR MAS. The grades of disc degeneration on the Pfirrmann scale were correlated with the metabolite concentrations.

RESULTS

Spectral analyses of the intervertebral discs with Pfirrmann grades IV and V demonstrated significantly higher concentrations of creatine, glycine, hydroxyproline, alanine, leucine, valine, acetate, isoleucine, α,β-glucose, and myo-inositol, and a lower intensity of the N-acetyl peak of chondroitin sulfate, compared to the spectra with Pfirrmann grade III.

CONCLUSION

Our results demonstrate correlations between metabolite concentrations and the degree of lumbar disc degeneration assessed using the Pfirrmann grading system and provide another step toward the potential use of in vivo MR spectroscopy for investigation of biomarkers in lumbar disc degeneration.

Immediate changes in spinal height and pain after aquatic vertical traction in patients with persistent low back symptoms: a crossover clinical trial

OBJECTIVE

To investigate the effect of aquatic vertical traction on spinal height, pain intensity, and centralization response compared with a land-based supine flexion position for patients with low back pain and signs of nerve root compression.

DESIGN

Single-blind, repeated-measures crossover design.

SETTING

Outpatient physical therapy clinic.

SUBJECTS

Ninety-eight subjects were recruited using consecutive sampling, with 28 men and 32 women of a mean ± standard deviation (SD) age of 59.6 ± 11.6 years completing testing.

INTERVENTION

Each subject participated in 2 sessions that consisted of loaded walking for 15 minutes, followed by either 15 minutes of land-based supine position or 15 minutes of aquatic vertical traction.

MEASUREMENTS

Spinal height change, measured using a commercial stadiometer, was determined after completing loaded walking and after each intervention.

RESULTS

The mean ± SD height change of 4.99 ± 2.88 mm after aquatic vertical traction was similar to that of 4.21 ± 2.53 mm after the land-based supine flexion (P = .0969). Paired t-test indicated that both interventions resulted in significant increased height (P < .0001). Decreases in pain after aquatic intervention (2.7 ± 2.1 cm) were significantly greater than decreases after land intervention (1.7 ± 1.7 cm; P = .0034), and centralization of symptoms was more pronounced after aquatic vertical suspension compared with the supine land-based flexion condition (P < .0001). A significant correlation between height change and both pain reduction (r = 0.39; P = .001) and centralization (r = 0.29; P = .013) was observed for the aquatic intervention only.

CONCLUSION

Although both the aquatic and land interventions produced significant increases in overall spinal height, the aquatic intervention produced greater pain relief and centralization response in subjects with low back pain and signs of nerve root compression.