Biomechanical study of the spinal cord in thoracic ossification of the posterior longitudinal ligament

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Objective: Although there are several classifications for cervical myelopathy, these do not take differences between spinal cord segments into account. Moreover, there has been no report of stress analyses for individual segments to date. Methods: By using the finite element method, we constructed 3-dimensional spinal cord models comprised of gray matter, white matter, and pia mater of the second to eighth cervical vertebrae (C2-C8). We placed compression components (disc and yellow ligament) at the front and back of these models, and applied compression to the posterior section covering 10%, 20%, 30%, or 40% of the anteroposterior diameter of each cervical spinal cord segment. Results: Our results revealed that, under compression applied to an area covering 10%, 20%, or 30% of the anteroposterior diameter of the cervical spinal cord segment, sites of increased stress varied depending on the morphology of each cervical spinal cord segment. Under 40% compression, stress was increased in the gray matter, lateral funiculus, and posterior funiculus of all spinal cord segments, and stress differences between the segments were smaller. Conclusion: These results indicate that, under moderate compression, sites of increased stress vary depending on the morphology of each spinal cord segment or the shape of compression components, and also that the variability of symptoms may depend on the direction of compression. However, under severe compression, the differences among the cervical spinal segments are smaller, which may facilitate diagnosis.

Section: -19mentioning

confidence: 99%

Stress analysis of the cervical spinal cord: Impact of the morphology of spinal cord segments on stress

Nishida

Kanchiku

Imajo

et al. 2016

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“…Our first goal was to develop a 3D-FEM spinal cord model that simulates the clinical situation, while our second goal was to analyze the clinical condition of patients. Similar to previous studies by Kato et al, [14][15][16] Li and Dai, 17,18 and Nishida et al, [19][20][21] bovine spinal cord was used in the current analytical model since it was impossible to obtain fresh human spinal cord. The mechanical properties of the spinal cord used in our study were similar to earlier reports.…”

Section: Discussionmentioning

confidence: 86%

“…The mechanical properties of the spinal cord used in our study were similar to earlier reports. [15][16][17][18][19][20][21] Li et al noted that it was reasonable to use the mechanical properties of bovine spinal cord because the brain and spinal cord of cattle and humans show similar injury-induced changes. 17 For the purpose of this study, we therefore assumed that the mechanical properties of spinal cord from these two species were similar.…”

Section: Discussionmentioning

confidence: 99%

Cervical ossification of the posterior longitudinal ligament: Biomechanical analysis of the influence of static and dynamic factors

Nishida¹,

Kanchiku²,

Kato³

et al. 2014

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Objective: Cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is induced by static factors, dynamic factors, or a combination of both. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions in the cervical spinal cord under static compression, dynamic compression, or a combination of both in the context of OPLL. Methods: Experimental conditions were established for the 3D-FEM spinal cord, lamina, and hill-shaped OPLL.To simulate static compression of the spinal cord, anterior compression at 10, 20, and 30% of the anterior-posterior diameter of the spinal cord was applied by the OPLL. To simulate dynamic compression, the OPLL was rotated 5°, 10°, and 15°in the flexion direction. To simulate combined static and dynamic compression under 10 and 20% anterior static compression, the OPLL was rotated 5°, 10°, and 15°in the flexion direction. Results: The stress distribution in the spinal cord increased following static and dynamic compression by cervical OPLL. However, the stress distribution did not increase throughout the entire spinal cord. For combined static and dynamic compression, the stress distribution increased as the static compression increased, even for a mild range of motion (ROM). Conclusion: Symptoms may appear under static or dynamic compression only. However, under static compression, the stress distribution increases with the ROM of the responsible level and this makes it very likely that symptoms will worsen. We conclude that cervical OPLL myelopathy is induced by static factors, dynamic factors, and a combination of both.

“…28 Although postoperative analysis of thoracic OPLL was also performed, this analysis targeted behaviors of the spinal cord, without mentioning mobility of anterior compression. 29 With the analysis models developed in the present study, mobility of anterior components was assessed. As a result, models matched to the clinical features were developed in terms of the pathology of OPLL and postoperative outcomes, and the conventional analysis was further improved.…”

Section: Discussionmentioning

confidence: 99%

Cervical ossification of the posterior longitudinal ligament: factors affecting the effect of posterior decompression

Nishida

Kanchiku

Kato

et al. 2016

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Objective: Decompression procedures for cervical myelopathy of ossification of the posterior longitudinal ligament (OPLL) are anterior decompression with fusion, laminoplasty, and posterior decompression with fusion. Preoperative and postoperative stress analyses were performed for compression from hill-shaped cervical OPLL using 3-dimensional finite element method (FEM) spinal cord models. Methods: Three FEM models of vertebral arch, OPLL, and spinal cord were used to develop preoperative compression models of the spinal cord to which 10%, 20%, and 30% compression was applied; a posterior compression with fusion model of the posteriorly shifted vertebral arch; an advanced kyphosis model following posterior decompression with the spinal cord stretched in the kyphotic direction; and a combined model of advanced kyphosis following posterior decompression and intervertebral mobility. The combined model had discontinuity in the middle of OPLL, assuming the presence of residual intervertebral mobility at the level of maximum cord compression, and the spinal cord was mobile according to flexion of vertebral bodies by 5°, 10°, and 15°. Results: In the preoperative compression model, intraspinal stress increased as compression increased. In the posterior decompression with fusion model, intraspinal stress decreased, but partially persisted under 30% compression. In the advanced kyphosis model, intraspinal stress increased again. As anterior compression was higher, the stress increased more. In the advanced kyphosis + intervertebral mobility model, intraspinal stress increased more than in the only advanced kyphosis model following decompression. Intraspinal stress increased more as intervertebral mobility increased. Conclusion: In high residual compression or instability after posterior decompression, anterior decompression with fusion or posterior decompression with instrumented fusion should be considered.