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Yusuke Tanabe, Kazuki Sakata, Hiromu Yamada, Takao Ito and Mitsuaki Takada

✓ Subarachnoid hemorrhage (SAH) was produced experimentally by injecting normal dog's blood as well as reserpinized dog's blood into the chiasmal cistern of the dog. The following observations were made: 1) After SAH with normal dog's blood, the intima of the basal truncal arterial wall showed some or all of such ultrastructural changes as appearance of vacuoles and dense bodies in endothelial cells, detachment of endothelial cells, appearance of intimal cells, and intimal thickening. The changes first appeared 2 hours after SAH, culminated at 3 to 7 days after SAH, and persisted up to 1 month after SAH. 2) After SAH with normal dog's blood, the media of the basal truncal arterial wall showed some or all of such ultrastructural changes as moth-eaten contour of muscle cells, appearance of intracytoplasmic vacuoles and dense bodies, appearance of cell debris, enlargement of interstitial space, and appearance therein of dense particles. These findings, which, in short, are to be expressed as myonecrosis and its repairing process, first appeared 2 hours after SAH, culminated at 1 to 4 months after SAH, and persisted up to 1 year after SAH. 3) Three and 5 days following SAH with reserpinized dog's blood, ultrastructural findings of the intima and media of the basal truncal arterial wall were entirely normal.

On the basis of the above findings, it was concluded that the ultrastructural changes in the cerebral arterial wall observed after SAH with normal dog's blood occurred as a consequence of vasospasm. The possibility that late spasm, in turn, might be facilitated by myonecrosis, could not be denied.

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Masahiko Miyata, Masashi Neo, Hiromu Ito, Makoto Yoshida, Shunsuke Fujibayashi and Takashi Nakamura

Object

Vertebral artery (VA) injury is a potentially serious complication of C-2 pedicle screw (PS) fixation. Although this surgery is frequently performed in patients with rheumatoid arthritis (RA), few studies have compared the risk of VA injury in patients with and without RA. In this study, the authors compare the morphological risk of VA injury relating to C-2 PS fixation in patients with and without RA.

Methods

A total of 110 3D CT images of the cervical spine including the axis were evaluated. Fifty patients with RA and 60 patients without RA were included in the study. The maximum PS diameter (MPSD) that could be used at C-2 without breaching the cortex was measured in 3D using a computer-assisted navigation system. A narrow-pedicle carrier was defined as a patient with an MPSD of 4 mm or less.

Results

In the RA group, 42 of 100 MPSDs were ≤ 4 mm, and 30 of 50 patients (60%) were narrow-pedicle carriers. In the non-RA group, 10 of 120 MPSDs (8%) were ≤ 4 mm, and 8 of 60 (13%) patients were narrow-pedicle carriers. The MPSD, the anteroposterior (AP) diameter of C-3, and the ratio of MPSD to the AP diameter of C-3 were significantly smaller in the RA group than in the non-RA group. Multiple logistic regression analysis showed that RA and narrow C-3 AP diameter were significant risk factors for a narrow-pedicle carrier.

Conclusions

Rheumatoid arthritis is a significant risk factor for a narrow C-2 pedicle. When performing PS placement at C-2, particularly in patients with RA, thorough preoperative evaluation of the bone architecture is very important for avoiding inadvertent injury to the VA.

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Kazuaki Morizane, Mitsuru Takemoto, Masashi Neo, Shunsuke Fujibayashi, Bungo Otsuki, Shimei Tanida, Takayoshi Shimizu, Hiromu Ito and Shuichi Matsuda

OBJECTIVE

Dyspnea and/or dysphagia is a life-threatening complication after occipitocervical fusion. The occiput-C2 angle (O-C2a) is useful for preventing dyspnea and/or dysphagia because O-C2a affects the oropharyngeal space. However, O-C2a is unreliable in atlantoaxial subluxation (AAS) because it does not reflect the translational motion of the cranium to C2, another factor affecting oropharyngeal area in patients with rheumatoid arthritis (RA) who have reducible AAS. The authors previously proposed the occipital and external acoustic meatus to axis angle (O-EAa; i.e., the angle made by McGregor’s line and a line joining the external auditory canal and the middle point of the endplate of the axis [EA line]) as a novel, useful, and powerful predictor of the anterior-posterior narrowest oropharyngeal airway space (nPAS) distance in healthy subjects. The aim of the present study was to elucidate the validity of O-EAa as an indicator of oropharyngeal airway space in RA patients with AAS.

METHODS

The authors investigated 64 patients with RA. The authors collected lateral cervical radiographs at neutral position, flexion, extension, protrusion, and retraction and measured the O-C2a, C2-C6, O-EAa, anterior atlantodental interval (AADI), and nPAS. Patients were classified into 2 groups according to the presence of AAS and its mobility: group N, patients without AAS; and group R, patients with reducible AAS during dynamic cervical movement.

RESULTS

Group N had a significantly lower AADI and O-EAa than group R in all but the extension position. The O-EAa was a better predictor for nPAS than O-C2a according to the mixed-effects models in both groups (marginal R2: 0.510 and 0.575 for the O-C2a and O-EAa models in group N, and 0.250 and 0.390 for the same models, respectively, in group R).

CONCLUSIONS

O-EAa was superior to O-C2a in predicting nPAS, especially in the case of AAS, because it affects both O-C2a and cranial translational motion. O-EAa would be a useful parameter for surgeons performing occipitocervical fusion in patients with AAS.