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Biomechanical study of cervical flexion myelopathy using a three-dimensional finite element method.

OBJECT
The goal of this study was to perform a biomechanical study of cervical flexion myelopathy (CFM) using a finite element method.


METHODS
A 3D finite element model of the spinal cord was established consisting of gray matter, white matter, and pia mater. After the application of semi-static compression, the model underwent anterior flexion to simulate CFM. The flexion angles used were 5 degrees and 10 degrees , and stress distributions inside the spinal cord were then evaluated.


RESULTS
Stresses on the spinal cord were very low under semi-static compression but increased after 5 degrees of flexion was applied. Stresses were concentrated in the gray matter, especially the anterior and posterior horns. The stresses became much higher after application of 10 degrees of flexion and were observed in the gray matter, posterior funiculus, and a portion of the lateral funiculus.


CONCLUSIONS
The 5 degrees model was considered to represent the mild type of CFM. This type corresponds to the cases described in the original report by Hirayama and colleagues. The main symptom of this type of CFM is muscle atrophy and weakness caused by the lesion of the anterior horn. The 10 degrees model was considered to represent a severe type of CFM and was associated with lesions in the posterior fand lateral funiculi. This type of CFM corresponds to the more recently reported clinical cases with combined long tract signs and sensory disturbance.