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Yasuaki Imajo, Tsukasa Kanchiku, Yuichiro Yoshida, Norihiro Nishida, and Toshihiko Taguchi

Here the authors report the case of a fresh vertebral body fracture with a large spinal intraosseous arteriovenous fistula (AVF). A 74-year-old woman started to experience low-back pain following a rear-end car collision. Plain radiography showed diffuse idiopathic skeletal hyperostosis (DISH). Sagittal CT sections revealed a transverse fracture of the L-4 vertebral body with a bone defect. Sagittal fat-suppressed T2-weighted MRI revealed a flow void in the fractured vertebra. Spinal angiography revealed an intraosseous AVF with a feeder from the right L-4 segmental artery. A fresh fracture of the L-4 vertebral body with a spinal intraosseous AVF was diagnosed. Observation of a flow void in the vertebral body on fat-suppressed T2-weighted MRI was important for the diagnosis of the spinal intraosseous AVF. Because conservative treatment was ineffective, surgery was undertaken. The day before surgery, embolization through the right L-4 segmental artery was performed using 2 coils to achieve AVF closure. Posterolateral fusion with instrumentation at the T12–S2 vertebral levels was performed without L-4 vertebroplasty. The spinal intraosseous AVF had disappeared after 4 months. At 24 months after surgery, the bone defect was completely replaced by bone and the patient experienced no limitations in daily activities. Given their experience with the present case, the authors believe that performing vertebroplasty or anterior reconstruction may not be necessary in treating spinal intraosseous AVF.

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Yoshihiko Kato, Yasuaki Imajo, Tsukasa Kanchiku, Takanori Kojima, Hideo Kataoka, and Toshihiko Taguchi

Cervical flexion myelopathy is thought to arise following compression of the spinal cord by vertebrae or intervertebral discs and dura mater, or from overstretching of the spinal cord induced by cervical spinal flexion. However, the influence of spinal flexion on the spinal cord and the detailed origins of this disease are unknown. In this article the authors report a case of cervical flexion myelopathy in which dynamic electrophysiological examination was performed using an epidural electrode. This investigation showed the real-time influence of flexion of the cervical spine on spinal cord function. This technique was considered to be useful for diagnosis and in decision making for treatment. Anterior fusion was the optimal surgical method for treating this disease.

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Masahiro Funaba, Yasuaki Imajo, Hidenori Suzuki, Norihiro Nishida, Yuji Nagao, Takuya Sakamoto, Kazuhiro Fujimoto, and Takashi Sakai

OBJECTIVE

Neurological and imaging findings play significant roles in the diagnosis of degenerative cervical myelopathy (DCM). Consistency between neurological and imaging findings is important for diagnosing DCM. The reasons why neurological findings exhibit varying sensitivity for DCM and their associations with radiological findings are unclear. This study aimed to identify associations between radiological parameters and neurological findings in DCM and elucidate the utility of concordance between imaging and neurological findings for diagnosing DCM.

METHODS

One hundred twenty-one patients with DCM were enrolled. The Japanese Orthopaedic Association (JOA) score, radiological parameters, MRI and kinematic CT myelography (CTM) parameters, and the affected spinal level (according to multimodal spinal cord evoked potential examinations) were assessed. Kinematic CTM was conducted with neutral positioning or at maximal extension or flexion of the cervical spine. The cross-sectional area (CSA) of the spinal cord, dynamic change in the CSA, C2–7 range of motion, and C2–7 angle were measured. The associations between radiological parameters and hyperreflexia, the Hoffmann reflex, the Babinski sign, and positional sense were analyzed via multiple logistic regression analysis.

RESULTS

In univariate analyses, the upper- and lower-limb JOA scores were found to be significantly associated with a positive Hoffmann reflex and a positive Babinski sign, respectively. In the multivariate analysis, a positive Hoffmann reflex was associated with a higher MRI grade (p = 0.026, OR 2.23) and a responsible level other than C6–7 (p = 0.0017, OR 0.061). A small CSA during flexion was found to be significantly associated with a positive Babinski sign (p = 0.021, OR 0.90). The presence of ossification of the posterior longitudinal ligament (p = 0.0045, OR 0.31) and a larger C2–7 angle during flexion (p = 0.01, OR 0.89) were significantly associated with abnormal great toe proprioception (GTP).

CONCLUSIONS

This study found that the Hoffmann reflex is associated with chronic and severe spinal cord compression but not the dynamic factors. The Babinski sign is associated with severe spinal cord compression during neck flexion. The GTP is associated with large cervical lordosis. These imaging features can help us understand the characteristics of the neurological findings.

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Yoshihiko Kato, Tsukasa Kanchiku, Yasuaki Imajo, Kotaro Kimura, Kazuhiko Ichihara, Syunichi Kawano, Daisuke Hamanaka, Kentaro Yaji, and Toshihiko Taguchi

Object

The authors evaluated the biomechanical effect of 3 different degrees of static compression in a model of the spinal cord in order to investigate the effect of cord compression in patients with ossification of the posterior longitudinal ligament (OPLL).

Methods

A 3D finite element spinal cord model consisting of gray matter, white matter, and pia mater was established. As a simulation of OPLL-induced compression, a rigid plate compressed the anterior surface of the cord. The degrees of compression were 10, 20, and 40% of the anteroposterior (AP) diameter of the cord. The cord was supported from behind by the rigid body along its the posterior border, simulating the lamina. Stress distributions inside of the cord were evaluated.

Results

The stresses on the cord were very low under 10% compression. At 20% compression, the stresses on the cord increased very slightly. At 40% compression, the stresses on the cord became much higher than with 20% compression, and high stress distributions were observed in gray matter and the lateral and posterior funiculus. The stresses on the compressed layers were much higher than those on the uncompressed layer.

Conclusions

The stress distributions at 10 and 20% compression of the AP diameter of the spinal cord were very low. The stress distribution at 40% compression was much higher. The authors conclude that a critical point may exist between 20 and 40% compression of the AP diameter of the cord such that when the degree of the compression exceeds this point, the stress distribution becomes much higher, and that this may contribute to myelopathy.

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Yoshihiko Kato, Hideo Kataoka, Kazuhiko Ichihara, Yasuaki Imajo, Takanori Kojima, Shunichi Kawano, Daisuke Hamanaka, Kentaro Yaji, and Toshihiko Taguchi

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° and 10°, 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° 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° of flexion and were observed in the gray matter, posterior funiculus, and a portion of the lateral funiculus.

Conclusions

The 5° 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° 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.