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Study Finds Evidence Asymmetrical Postures During Loading Contribute to Disc Failure

disc failure

A microstructural analysis of how healthy discs respond to compression and complex loading postures—specifically those incorporating flexion and facet-constrained shear—found evidence that the required load contributing to disc failure was reduced when complex postures, rather than simple flexion, were utilized in load-bearing situations. In addition, when asymmetric postures were used during lifting, rather than simple compression or flexion, there occurred more infiltration of the nucleus material as it made its way to the annular periphery. The results of the study indicate that asymmetric postures during lifting are more likely to contribute to disc degeneration and lower back pain and should therefore be avoided.

The Study

The study 1 involved 30 motion segments from 10 sheep spines that had no previous signs of disc degeneration. The discs were frozen, thawed, and then rehydrated fully prior to the compression experiments to be in agreement with previous similar experiments and maximize the annular load. Researchers created a bending, twisting, lifting scenario that involved axial rotation, lateral, anterior, and posterior shear, and flexion, adapting the mechanical rig to compress and rotate the disc segments to failure using compressive force.

The typical failure was lower under complex loading conditions than in conditions of simple flexion. Microstructural damage included fractures of the vertebrae and three variations of annular damage, including mid-span direct tearing, non-continuous mid-span tearing, and annular-endplate tearing. Combinations of all three types of damage occurred, as well as circumferential failure, in all 30 discs.

The complex postures utilized in the study lessened the discs abilities to withstand compressive loading and contributed to failures. The complex loading conditions contributed to instances of dual modes of failure, including the circumferential (circuitous tracking of nuclear materials towards the annular periphery) evident in all study samples. This suggests that the lateral parts of the disc may be especially vulnerable during flexion because of shear loading in the area. Circumferential damage was evident in all 30 discs involved in this study, which suggests that it is likely an important type of damage involved in disc failure under complex loading conditions.

Conclusion

Complex postures during load-lifting may contribute to herniation and disc failure. Asymmetrical postures (in addition to flexion) should be avoided during lifting to reduce the likelihood of sustaining a lower back injury.

 

KEYWORDS: complex loading, disc failure, asymmetrical postures during loading, compression and complex loading postures, flexion and facet-constrained shear, disc degeneration, annular damage, disc herniation

Summary
Asymmetrical loading and disc failure - Lift properly
Article Name
Asymmetrical loading and disc failure - Lift properly
Description
Study showed that asymmetrical loading of the lumbar spine during loading is a risk factor for disc herniation.
Author
Publisher Name
Dynamic Disc Designs
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