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

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

Lumbar foraminal stenosis is a common cause of lumbar radiculopathy and conventionally assessed with magnetic resonance imaging (MRI) in supine-positioned patients. An MRI acquired during spine loading may unmask pathology not otherwise revealed in a relaxed position. Therefore, we investigated how spine loading during MRI affects lumbar foramina. In 89 low-back pain patients’ lumbar, MRIs were performed in a relaxed supine position and during axial loading using a Dynawell^® compression device. The smallest area of all intervertebral foramina at levels L3/L4–L5/S1 (534 foramina) was determined using a freehand polygonal tool in parasagittal T2-weighted sequences. The grading system described by Lee et al. was also used to qualitatively assess foraminal stenosis. Overall, a mean reduction of 2.2% (mean −0.89 cm² and −0.87 cm², respectively) was observed (p = 0.002), however for individual foramina large variations, with up to about 50% increase or decrease, were seen. Stratified for lumbar level, an area reduction was found for L3/L4 and L4/L5 foramina (mean change −0.03 cm²; p = 0.036; and −0.03 cm²; p = 0.004, respectively) but not for L5/S1. When comparing the measured area changes to qualitative foraminal grading, 22% of the foramina with a measured area decrease were evaluated with a higher grading. Thus, detailed information on foraminal appearance and nerve root affection can be obtained using this method.

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

PURPOSE

Adjacent segment disease (ASD) constitutes a long-term complication of instrumented spinal fusion. Aim of this study is to analyze the utilization of percutaneous transforaminal endoscopic discectomy (PTED) for the treatment of symptomatic ASD, emphasizing basically in the postoperative course.

METHODS

A prospective study with 35 patients was designed. Patients enrolled in our study were distributed in two different groups. Group A constituted of 15 patients featuring ASD as a complication of a previously conducted lumbar spinal fusion. Group B was composed of 20 patients, presenting simple lumbar disc herniation (LDH). All patients were subjected to successful PTED for LDH. Patients were evaluated at regular intervals in 6-week and 3-, 6-, and 12-month postoperatively. Visual analog scale was utilized for leg (VAS-LP) and low back pain (VAS-BP) evaluation. Health-related quality of life was assessed with short-form 36 health survey questionnaire (SF-36).

RESULTS

VAS-BP scores were statistically significantly differentiated between the two groups in all intervals of follow-up. In contrast, VAS-LP scores demonstrated statistically significant differentiation in none of follow-up intervals, indicating similar results between the two groups. Maximal improvement was in both cases for all patients observed in 6-week postoperatively, with subsequent stabilization. SF-36 preoperative evaluation denoted a statistically significant differentiation in bodily pain and role emotional parameters, which was continually until the end of follow-up observed. The other SF-36 parameters featured similar values between the two groups preoperatively as well as during the follow-up intervals.

CONCLUSION

PTED is capable of successfully dealing with LDH and furthermore with complications of fusion as ASD.

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

The biomechanical function of the intervertebral disc (IVD) is a critical indicator of tissue health and pathology. The mechanical responses (displacements, strain) of the IVD to physiologic movement can be spatially complex and depend on tissue architecture, consisting of distinct compositional regions and integrity; however, IVD biomechanics are predominately uncharacterized in vivo. Here, we measured voxel-level displacement and strain patterns in adjacent IVDs in vivo by coupling magnetic resonance imaging (MRI) with cyclic motion of the cervical spine. Across adjacent disc segments, cervical flexion-extension of 10° resulted in first principal and maximum shear strains approaching 10%. Intratissue spatial analysis of the cervical IVDs, not possible with conventional techniques, revealed elevated maximum shear strains located in the posterior disc (nucleus pulposus) regions. IVD structure, based on relaxometric patterns of T₂ and T_1ρ images, did not correlate spatially with functional metrics of strain. Our approach enables a comprehensive IVD biomechanical analysis of voxel-level, intratissue strain patterns in adjacent discs in vivo, which are largely independent of MRI relaxometry. The spatial mapping of IVD biomechanics in vivo provides a functional assessment of adjacent IVDs in subjects, and provides foundational biomarkers for elastography, differentiation of disease state, and evaluation of treatment efficacy.

[Vertebral three-dimensional motion characteristics of adjacent segments in patients with isthmic spondylolisthesis in vivo]

Objective

To observe vertebral three-dimensional motion characteristics of adjacent segments in patients with symptomatic L 4 isthmic spondylolisthesis (IS).

Methods

Fourteen symptomatic L 4 IS patients who underwent surgery treatment (trial group) and 15 asymptomatic volunteers without back pain and other lesions of spine (control group) were recruited. There was no significant difference in gender, age, body mass index, and bone mineral density between the two groups ( P>0.05). The three-dimensional reconstruction model of lumbar spine was acquired from the thin slice CT of the lumbar spine of the subjects by combining dual-X-ray fluoroscopy imaging system with spiral CT examination. The model was matched to the double oblique X-ray fluoroscopy images captured by dual-X-ray fluoroscopy imaging system at different active positions of the lumbar spine to reproduce the three-dimensional instantaneous of lumbar spondylolisthesis at different state of motion. The motion and relative displacement of adjacent segments (L 3, 4 and L 5, S 1) of spondylolisthesis were measured quantitatively by establishing a three-dimensional coordinate system at the geometric center of the vertebral body. The results were compared with those of the control group.

Results

When L 3, 4 in the control group were flexed flexion-extension, left-right twisting, and left-right bending, and when L 5, S 1 in the control group were flexed left-right twisting and left-right bending, the activity along the main axis of motion (main axis of motion) tended to increase compared with that along the corresponding coupled axis of motion (secondary axis of motion); however, this trend disappeared in the trial group, and the main and secondary movements were disordered. Because of the coronal orientation of the facet joints of L 5, S 1, the degree of motion along the main axis of motion decreased during flexion and extension, but this trend disappeared in the trial group. Compared with the control group, L 3, 4 in the trial group exhibited displacement instability in flexion-extension, left-right twisting, and left-right bending ( P<0.05); there was no significant difference in the relative displacement of L 5, S 1 intervertebral bodies along x, y, and z axes between the trial group and the control group in flexion-extension, left-right twisting, and left-right bending curvature ( P>0.05).

Conclusion

Patients with symptomatic L 4 IS have disorders of primary and secondary movement patterns in adjacent segments, while IS showed significantly displacement instability in L 3, 4 and significantly decreased motion in L 5, S 1.