Tensile mechanical analysis of anisotropy and velocity dependence of the spinal cord white matter: a biomechanical study

Nishida, Norihiro; Sakuramoto, Itsuo; Fujii, Yoshiyuki; Hutama, Rudolf Yoga; Jiang, Fei; Ohgi, Junji; Imajo, Yasuaki; Suzuki, Hitomi; Funaba, Masahiro; Chen, Xian; Sakai, Takashi

doi:10.4103/1673-5374.313059

Cited by 5 publications

(3 citation statements)

References 28 publications

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“…The kinetic energy of spinal cord tissue increases with the square of its velocity value (E = m*v 2 ; E = energy; m = mass; v = velocity), suggesting increased dynamic mechanical strain with increasing velocities during oscillations. In a bovine model could be demonstrated that mechanical strain parallel to white matter fiber direction (i.e., tissue stretch) increased cord tissue stress and stress levels increased with higher velocities of external forces ( 40 ). Recently, a computational model additionally demonstrated mechanical strain to the spinal cord caused by cord motion/oscillations comparable to a dynamic compression model during spine flexion and extension ( 20 ).…”

Section: Discussionmentioning

confidence: 99%

Potential thresholds of critically increased cardiac-related spinal cord motion in degenerative cervical myelopathy

Pfender,

Jutzeler,

Hubli

et al. 2024

Front. Neurol.

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IntroductionNew diagnostic techniques are a substantial research focus in degenerative cervical myelopathy (DCM). This cross-sectional study determined the significance of cardiac-related spinal cord motion and the extent of spinal stenosis as indicators of mechanical strain on the cord.MethodsEighty-four DCM patients underwent MRI/clinical assessments and were classified as MRI+ [T2-weighted (T2w) hyperintense lesion in MRI] or MRI− (no T2w-hyperintense lesion). Cord motion (displacement assessed by phase-contrast MRI) and spinal stenosis [adapted spinal canal occupation ratio (aSCOR)] were related to neurological (sensory/motor) and neurophysiological readouts [contact heat evoked potentials (CHEPs)] by receiver operating characteristic (ROC) analysis.ResultsMRI+ patients (N = 31; 36.9%) were more impaired compared to MRI− patients (N = 53; 63.1%) based on the modified Japanese Orthopedic Association (mJOA) subscores for upper {MRI+ [median (Interquartile range)]: 4 (4–5); MRI−: 5 (5–5); p < 0.01} and lower extremity [MRI+: 6 (6–7); MRI−: 7 (6–7); p = 0.03] motor dysfunction and the monofilament score [MRI+: 21 (18–23); MRI−: 24 (22-24); p < 0.01]. Both patient groups showed similar extent of cord motion and stenosis. Only in the MRI− group displacement identified patients with pathologic assessments [trunk/lower extremity pin prick score (T/LEPP): AUC = 0.67, p = 0.03; CHEPs: AUC = 0.73, p = 0.01]. Cord motion thresholds: T/LEPP: 1.67 mm (sensitivity 84.6%, specificity 52.5%); CHEPs: 1.96 mm (sensitivity 83.3%, specificity 65.6%). The aSCOR failed to show any relation to the clinical assessments.DiscussionThese findings affirm cord motion measurements as a promising additional biomarker to improve the clinical workup and to enable timely surgical treatment particularly in MRI− DCM patients.Clinical trial registrationwww.clinicaltrials.gov, NCT 02170155.

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Section: Discussionmentioning

confidence: 99%

Potential thresholds of critically increased cardiac-related spinal cord motion in degenerative cervical myelopathy

Pfender,

Jutzeler,

Hubli

et al. 2024

Front. Neurol.

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“…To study the effects of tension on SWV, 9 incremental boundary loads (i.e., stresses) were applied to the virtual cord. The stresses ranged from 0 to 32 kPa at 4 kPa increments, modified from a recent biomechanical spinal cord study to overlap with our cadaveric benchtop model 65 .…”

Section: Methodsmentioning

confidence: 99%

Quantifying tethered spinal cord tension: Ultrasound elastography results from computational, cadaveric, and intraoperative first-in-human studies

Kerensky

Paul²,

Routkevitch³

et al. 2023

Preprint

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Background Tension in the spinal cord is a trademark of tethered cord syndrome. Unfortunately, existing tests cannot quantify tension across the bulk of the cord, making the diagnostic evaluation of stretch ambiguous. A potential non-destructive metric for spinal cord tension is ultrasound-derived shear wave velocity (SWV). The velocity is sensitive to tissue elasticity and boundary conditions including strain. We use the term Ultrasound Tensography to describe the acoustic evaluation of tension with SWV. Methods Our solution “Tethered cord Assessment with Ultrasound Tensography (TAUT)” was utilized in three sub-studies: finite element simulations, a cadaveric benchtop validation, and a neurosurgical case series. The simulation computed SWV for given tensile forces. The induced tension cadaveric model validated the SWV-tension relationship. Lastly, SWV was measured intraoperatively in patients diagnosed with tethered cord who underwent surgical treatment (spinal column shortening). The surgery alleviates tension by decreasing the vertebral column length. Results Here we observe a strong linear relationship between tension and squared SWV across the preclinical sub-studies. Higher tension induces faster shear waves in the simulation (R2 = 0.984) and cadaveric (R2 = 0.951) models. The SWV decreases in all neurosurgical procedures (p<0.001). Moreover, TAUT has a c-statistic of 0.962 (0.92-1.00), detecting all tethered cords. Conclusions This study presents the first clinical metric of spinal cord tension. Strong agreement among computational, cadaveric, and clinical studies demonstrates the utility of ultrasound-induced SWV for quantitative intraoperative feedback. This technology is positioned to enhance tethered cord diagnosis, treatment, and post-operative monitoring as it differentiates stretched from healthy cords.

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“…The kinetic energy of spinal cord tissue increases with the square of its velocity value (E = m*v 2 ; E = energy; m = mass; v = velocity), suggesting increased dynamic mechanical strain with increasing velocities during oscillations. In a bovine model could be demonstrated that mechanical strain parallel to white matter fiber direction (i.e., tissue stretch) increased cord tissue stress and stress levels increased with higher velocities of external forces (40). Recently, a computational model additionally demonstrated mechanical strain to the spinal cord caused by cord motion/oscillations comparable to a dynamic compression model during spine flexion and extension (20).…”

Section: Association Of Increased Motion To Pathologic Assessmentsmentioning

confidence: 99%

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Tensile mechanical analysis of anisotropy and velocity dependence of the spinal cord white matter: a biomechanical study

Cited by 5 publications

References 28 publications

Potential thresholds of critically increased cardiac-related spinal cord motion in degenerative cervical myelopathy

Potential thresholds of critically increased cardiac-related spinal cord motion in degenerative cervical myelopathy

Quantifying tethered spinal cord tension: Ultrasound elastography results from computational, cadaveric, and intraoperative first-in-human studies

Table_1.XLSX

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