Measurement of in vivo spinal cord displacement and strain fields of healthy and myelopathic cervical spinal cord

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OBJECTIVE

Cervical myelopathy (CM) is a common and debilitating form of spinal cord injury caused by chronic compression; however, little is known about the in vivo mechanics of the healthy spinal cord during motion and how these mechanics are altered in CM. The authors sought to measure 3D in vivo spinal cord displacement and strain fields from MR images obtained during physiological motion of healthy individuals and cervical myelopathic patients.

METHODS

Nineteen study participants, 9 healthy controls and 10 CM patients, were enrolled in the study. All study participants had 3T MR images acquired of the cervical spine in neutral, flexed, and extended positions. Displacement and strain fields and corresponding principal strain were obtained from the MR images using image registration.

RESULTS

The healthy spinal cord displaces superiorly in flexion and inferiorly in extension. Principal strain is evenly distributed along the spinal cord. The CM spinal cord displaces less than the healthy cord and the magnitude of principal strain is higher, at the midcervical levels.

CONCLUSIONS

Increased spinal cord compression during cervical myelopathy limits motion of the spinal cord and increases spinal cord strain during physiological motion. Future studies are needed to investigate how treatment, such as surgical intervention, affects spinal cord mechanics.

ABBREVIATIONS ccRatio = cord-canal ratio; CM = cervical myelopathy; JOA = Japanese Orthopaedic Association; LBDFT = landmark based deformation field transform.

Article Information

Correspondence Nicole M. Grosland: The University of Iowa, Iowa City, IA. nicole-grosland@uiowa.edu.

INCLUDE WHEN CITING Published online March 22, 2019; DOI: 10.3171/2018.12.SPINE18989.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Superior (positive values) and inferior (negative values) cervical spinal cord displacement of CM patients and healthy controls during flexion (upper) and extension (lower). Data are presented as mean ± standard deviation.

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    Maximum and minimum principal strain of healthy controls in flexion and extension. Data are presented as mean ± standard deviation.

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    Maximum and minimum principal strain of CM patients in flexion and extension. Data are presented as mean ± standard deviation.

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    MR image of healthy control subject in extension (left). White arrow indicates mild compression at C5–6 and C6–7. 3D figure of minimum and maximum principal Eulerian strain of the same subject’s spinal cord (right). Black arrows indicate areas of high compressive (left) and tensile (right) strains as a result of compression. Spinal cord roots are shown in gray. Figure is available in color online only.

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