Flexion model simulating spinal cord injury without radiographic abnormality in patients with ossification of the longitudinal ligament: the influence of flexion speed on the cervical spine.
OBJECTIVE
It is suspected that the speed of the motion of the spinal cord under static compression may be the cause of spinal cord injury (SCI). However, little is known about the relationship between the speed of the motion of the spinal cord and its stress distributions. The objective was to carry out a biomechanical study of SCI in patients with ossification of the longitudinal ligament without radiologic evidence of injury.


METHODS
A 3-dimensional finite element spinal cord model was established. After the application of static compression, the model underwent anterior flexion to simulate SCI in ossification of the longitudinal ligament patients without radiologic abnormality. Flexion of the spine was assumed to occur at 1 motor segment. Flexion angle was 5 degrees, and flexion speeds were 0.5 degrees/s, 5 degrees/s, and 50 degrees/s. Stress distributions inside of the spinal cord were evaluated.


RESULTS
Stresses on the spinal cord increased slightly after the application of 5 degrees of flexion at a speed of 0.5 degrees/s. Stresses became much higher at a speed of 5 degrees/s and increased further at 50 degrees s.


CONCLUSIONS
The stress distribution of the spinal cord under static compression increased with faster flexion speed of the spinal cord. High-speed motion of the spinal cord under static compression may be one of the causes of SCI in the absence of radiologic abnormality.
Kato
Yoshihiko
Y
Department of Orthopedic Surgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan. kato-yo@yamaguchi-u.ac.jp
Kanchiku
Tsukasa
T
Imajo
Yasuaki
Y
Ichinara
Kazuhiko
K
Kawano
Syunichi
S
Hamanama
Daiskue
D
Yaji
Kentaro
K
Taguchi
Toshihiko
T
D002574:Cervical Vertebrae / Q000503:physiopathology; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008953:Models, Anatomic; D017887:Ossification of Posterior Longitudinal Ligament / Q000150:complications*; D013119:Spinal Cord Injuries / Q000209:etiology*; D013131:Spine / Q000473:pathology*