The narrowing of the lumbar spinal canal during loaded MRI: the effects of the disc and ligamentum flavum

Abstract

Load and activity changes of the spine typically cause symptoms of nerve root compression in subjects with spinal stenosis. Protrusion of the intervertebral disc has been regarded as the main cause of the compression. The objective was to determine the changes in the size of the lumbar spinal canal and especially those caused by the ligamentum flavum and the disc during loaded MRI. For this purpose an interventional clinical study on consecutive patients was made. The lumbar spines in 24 supine patients were examined with MRI: first without any external load and then with an axial load corresponding to half the body weight. The effect of the load was determined through the cross-sectional areas of the spinal canal and the ligamentum flavum, the thickness of ligamentum flavum, the posterior bulge of the disc and the intervertebral angle. External load decreased the size of the spinal canal. Bulging of the ligamentum flavum contributed to between 50 and 85% of the spinal canal narrowing. It was concluded that the ligamentum flavum, not the disc had a dominating role for the load induced narrowing of the lumbar spinal canal, a finding that can improve the understanding of the patho-physiology in spinal stenosis.

Increased Facet Fluid Predicts Dynamic Changes in the Dural Sac Size on Axial-Loaded MRI in Patients with Lumbar Spinal Canal Stenosis

“…In evaluating the severity of spinal canal narrowing, the dural sac cross-sectional area (DCSA) is frequently measured by using axial MR images. [1][2][3][4][5][6] However, conventional MR imaging is performed with the patient in the supine position, and the DCSA may be larger in this position than in the standing position. 3,4,7 Hence, conventional MR imaging carries a risk of underestimating the severity of spinal canal narrowing.…”

“…Axial-loaded MR imaging may induce a significant reduction in the DCSA and potentially show additional imaging findings that cannot be acquired on conventional MR imaging. 3,4,6,8 The DCSA on axial-loaded MR imaging has been reported to correlate with the severity of clinical symptoms in patients with LSCS. 9 Furthermore, previous studies have demonstrated that a dynamic decrease in the DCSA induced by axial loading increases the diagnostic specificity of spinal canal narrowing and influences the indications for surgical treatment.…”

Indications for prophylactic lumbar decompression at the L3/4 level in patients with L4/5 responsible lumbar spinal canal stenosis

“…Recently, some researchers have reported a device that can apply axial loading to the lumbar spine of patients in the supine position during MRI 10,[23][24][25][26] . Use of the device could induce significant narrowing of the spinal canal and provide valuable information that was not detected by conventional MRI [23][24][25][26] .…”

“…Use of the device could induce significant narrowing of the spinal canal and provide valuable information that was not detected by conventional MRI [23][24][25][26] . Kanno et al 27) described that the DCSA on axial-loaded MRI was significantly correlated with the severity of the symptoms.…”

Variations in Morphology of Lumbar Spinal Canal In Degenerative Discopathy

“…Domed disc has been recognized as a major cause of compression. Hansson et al [17] evaluated the change in the size of the lumbar spinal canal in patients with discectomy and bold ligamentum flavum. the authors concluded that an overload of the lumbar spine can produce changes in the intervertebral discs but also in the yellow ligaments which, likewise, are bulging, and are actively involved in the pathogenesis of spinal canal stenosis causing stenosis of up to 50-85%.…”