In Vivo Characteristics of Nondegenerated Adjacent Segment Intervertebral Foramina in Patients With Degenerative Disc Disease During Flexion-Extension

Abstract

Study Design In vivo patient biomechanical study. Objective To investigate the dimensions of lumbar intervertebral foramen (LIVF) of patients with degenerative disc disease (DDD) during a flexion-extension motion of the body. Summary of Background Data LIVF narrowing may result in nerve root compression. The area changes of degenerated and adjacent non-degenerated LIVFs in DDD patients under physiologic loading conditions are unknown. Methods Nine symptomatic low back pain patients with radiological evidence of L4-S1 DDD were recruited. Each subject was MRI scanned for construction of 3D lumbar vertebral models, and fluoroscopically imaged when the body extended from 45° flexion to full extension for reconstruction of LIVF dimensions. The data of the adjacent segment L3/4 and diseased segment L4/5 and L5/S1 were compared with a normal control group at 45° flexion, upright, and full extension of the body. Results The mean LIVF areas of DDD segments were significantly smaller than those of the normal subjects in all positions (p<0.05). In upright position, the LIVF areas of the DDD patients were 32.8% and 33.6% smaller than the normal subjects for L4/5 and L5/S1, respectively. For the adjacent L3/4, the LIVF area of the DDD patients was 32.3% smaller than that of the normal controls (p<0.05). The total change of L3/4 LIVF area in DDD patients from flexion to extension was significantly smaller than that of the normal subjects, but the changes in L4/5 and L5/S1 LIVF areas were similar between the two groups (p>0.05). Conclusion Similar reductions of the LIVF dimensions were observed at the adjacent and the involved levels of the DDD patients, implying that biomechanical changes might have already occurred at the adjacent segment despite the lack of radiographic evidence of degeneration. Subsequent research should focus on the effects of surgical fusion on the biomechanical features of the adjacent segment. Level of Evidence N/A

In vivo intervertebral disc deformation: intratissue strain patterns within adjacent discs during flexion–extension

“…Intratissue IVD strains have been reported indirectly with combinatorial methods (e.g. radiography and 3D modeling 53 – 55 and fluoroscopy/MRI 56 – 58 ) typically extrapolating displacement and strain fields from digital reconstruction of vertebral endplate movements. Nevertheless, to our knowledge, no in vivo studies report direct voxel-level intratissue strains from a single noninvasive modality, which demonstrates the improvement of dualMRI over more composite and conventional techniques (Fig.…”

Axial Loading during MRI Induces Lumbar Foraminal Area Changes and Has the Potential to Improve Diagnostics of Nerve Root Compromise

“…There are many factors, alone or in combination, that may affect specific foramen during the loading of the spine, e.g., disc degeneration degree in the actual level, the direction of the loading forces applied, disc height, disc angle [3,[6][7][8], and other potential factors, such as muscle tension. The effect of a specific loading situation on a single foramen both in real life (standing/sitting) and in a loaded supine position, particularly during an MRI, is difficult to predict.…”

“…Furthermore, specific pathologies not detected in an unloaded position may appear with loading, e.g., facet joint cysts [4,5]. The loading of the lumbar spine may influence foramina differently based on several factors, e.g., spinal segment level, disc angle, loading direction, and the degree of pathological changes [6][7][8][9]. However, despite reports on the influence of spinal loading on intervertebral foramina, no systematic work has evaluated the extent to which the intervertebral lumbar foramina are affected during axial loading of the lumbar spine.…”

Treatment of adjacent segment disease with percutaneous transforaminal endoscopic discectomy: Early experience and results

“…2 Regarding the biomechanics, reductions of the lumbar intervertebral foramina dimensions, which have been observed at the adjacent and the involved levels of patients with degenerative disc disease imply that similar changes occur at the ASD despite the lack of radiographic evidence of degeneration. 18 Additionally, adjacent segment Kapetanakis et al…”

“…Regarding the biomechanics, reductions of the lumbar intervertebral foramina dimensions, which have been observed at the adjacent and the involved levels of patients with degenerative disc disease imply that similar changes occur at the ASD despite the lack of radiographic evidence of degeneration. 18 Additionally, adjacent segment intervertebral joint loads have been linked to the degree of lordosis that is surgically imposed during vertebral fusion, indicating that an artificial decrease in lumbar lordosis caused by an L4/5 fusion lead to adverse loading conditions for the adjacent levels. 19…”