Goal of the Study?
Vertebral slippage (spondylolisthesis) can occur in the ageing spine. In listhesis, one vertebra is either forward or backwards relative to its adjacent vertebral partner in the vertebral column. In this research study 1, the authors looked at dynamic anterior (forward) slippage of the top vertebra relative to the lower because there is debate on whether these slippages are still moving or if the misalignment is stable. They were curious whether instability could be predicted with MRI alone.
Why are they doing this study?
Learning which (if any) vertebra(e) slip during everyday movements, related to pain syndromes, is essential when a surgical (or other therapeutic) intervention is considered. In this study conducted at the Spine Center in Denmark, all patients admitted undergo MRI to look for anatomical findings suspected of contributing to dynamic spondylolisthesis. The findings of interest include disc height loss, thickened ligamentum flavum, facet joint effusion, facet joint angle, and vacuum phenomenon. Currently, standing flexion/extension x-rays with a vertebral translation greater than 3mm are the most accurate technique to measure instability. However, some back pain sufferers may not be able to achieve full flexion/extension because of pain-limiting movements. Therefore, it would be helpful to glean more details from MRI imaging to help discern segmental instability.
The L4-5 joint level was the spinal level of interest in this study. Two hundred thirty-two patients with known lumbar segmental instability were retrospectively reviewed. MRI and radiographic images were evaluated for threshold values of disc height, facet joint angle and facet effusion. By combining these values on MRI, the hope was that MRI findings could predict what could be expected with flexion-extension radiographs and, ultimately, the degree of lumbar instability.
What did they find?
Of the 232 patients, 47 were stable, and 185 were unstable. The MRI findings that were found to be significant were:
- facet joint angle greater than 46 degrees
- bilateral joint effusion greater than 1.5mm
- disc height index (as a percentage loss of 13)
Vacuum phenomenon was NOT found to be statistically significant in this study.
Why do these findings matter?
Trying to predict dynamic motion from motionless MR imaging is crucial in the case of lumbar instability. This research demonstrated that when these MRI findings are looked at carefully, one can help predict instability on standing radiographs. This can be helpful not only in the case of surgical options but can also help in the conservative management of low back pain cases that may be related to hypermobility as well.
At Dynamic Disc Designs, we craft dynamic disc models to help clinicians explain MRI findings in a tangible and motivational way to foster a conservative management strategy. When patients can visualize their findings in a dynamic way, this can really help with the locus of control in the case of stability exercises and the movements that reduce the translation of shear forces. Teach and empower with ddd.