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  • Author or Editor: Kazuhiro Chiba x
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Masahiko Watanabe, Kazuhiro Chiba, Morio Matsumoto, Hirofumi Maruiwa, Yoshikazu Fujimura and Yoshiaki Toyama

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Masahiko Watanabe, Kazuhiro Chiba, Morio Matsumoto, Hirofumi Maruiwa, Yoshikazu Fujimura and Yoshiaki Toyama

Object. Spinal cord herniation is a rare cause of progressive myelopathy and can be corrected surgically. In most previous reports, closure of the dural defect was the recommended procedure. The object of this paper is to describe a new procedure in which spinal cord constriction is released by enlarging the hiatus; additionally the postoperative results will be discussed.

Methods. In nine patients with spinal cord herniation, enlargement of the dural defect was performed. In eight patients, neurological deficits resolved immediately after surgery. In one patient with a severe preoperative neurological deficit whose spinal cord herniated massively, deterioration occurred postoperatively. To date, no recurrence of herniation has been observed.

Conclusions. The goals of surgery are to reduce the herniation, return the spinal cord to the normal position, and prevent the recurrence of herniation. The use of sutures to close the dural defect has been the method of choice to date. The surgical space in front of the spinal cord, however, is insufficient to accommodate this procedure safely. Because symptoms are caused by the constriction of the spinal cord at the hiatus, surgical expansion of the hiatus allows the goals of surgery to be achieved. This procedure, which is technically easier and less invasive with regard to the vulnerable spinal cord than the closure of the dural defect, could be a viable alternative for the treatment of this rare disease.

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Morio Matsumoto, Kazuhiro Chiba, Takashi Tsuji, Hirofumi Maruiwa, Yoshiaki Toyama and Jun Ogawa

✓ The authors placed titanium mesh cages to achieve posterior atlantoaxial fixation in five patients with atlantoaxial instability caused by rheumatoid arthritis or os odontoideum. A mesh cage packed with autologous cancellous bone was placed between the C-1 posterior arch and the C-2 lamina and was tightly connected with titanium wires. Combined with the use of transarticular screws, this procedure provided very rigid fixation. Solid fusion was achieved in all patients without major complications. The advantages of this method include more stable fixation, better control of the atlantoaxial fixation angle, and reduced donor-site morbidity compared with a conventional atlantoaxial arthrodesis in which an autologous iliac crest graft is used.

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Ken Ishii, Kazuhiro Chiba, Masahiko Watanabe, Hiroo Yabe, Yoshikazu Fujimura and Yoshiaki Toyama

✓ Excision is the treatment of choice in cases of sacral chordoma. Local recurrences, however, have often been observed even after total en bloc resection. The authors assessed outcomes in four cases of tumor recurrence in patients who underwent total en bloc S2–3 resection for sacral chordomas that were located below S-3. The primary recurrences were located at either side of the lateral portion of the remaining sacrum in all patients. In two patients in whom preoperative magnetic resonance imaging indicated no invasion of the tumor into surrounding soft tissues, recurrence in the resected end of the gluteus maximus or piriformis muscle was also observed. The authors therefore recommend that the S2–3 sacrectomy should be performed over an adequate margin, including a part of sacroiliac joints at the bilateral portions of the sacrum and soft tissues such as the gluteus maximus or piriformis muscle.

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Yukihiko Obara, Morio Matsumoto, Kazuhiro Chiba, Hiroo Yabe, Yoshiaki Toyama and Makio Mukai

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Kenya Nojiri, Morio Matsumoto, Kazuhiro Chiba, Hirofumi Maruiwa, Masaya Nakamura, Takashi Nishizawa and Yoshiaki Toyama


The aim of this study was to establish standard values for the normal alignment of the upper cervical spine and to clarify its relationship with the lower cervical spine in terms of alignment.


Three hundred thirteen asymptomatic volunteers (155 men and 158 women) participated in this study. Lateral radiographs were obtained with the neck in neutral position, and the angles formed by the occiput (Oc) and the axis, the atlas and the axis, and C-2 to C-7 were measured. The mean Oc—C2 angle was 14.5 ± 8° in men and 16 ± 8.5° in women; the mean C1–2 angle was 26.5 ± 7° and 28.9 ± 6.7°, respectively; and the mean C2–7 angle was 16.2 ± 12.9° and 10.5 ± 10.3°, respectively. Although weak, statistically significant negative correlation was observed between Oc—C2 and C2–7 angles (r = −0.31 in men and −0.37 in women), and between C1–2 and C2–7 angles (r = −0.22 in men and −0.22 in women). The correlation coefficient between the Oc—C2 and C2–7 angles was greater than that between the C1–2 and C2–7 angles.


Such relationships between alignment of the upper and lower cervical spines should be taken into consideration when performing occipitocervical fusion.

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Masaya Nakamura, Kazuhiro Chiba, Takashi Nishizawa, Hirofumi Maruiwa, Morio Matsumoto and Yoshiaki Toyama

Object. Pain is one of the major symptoms in patients with syringomyelia; however, its origin is not fully understood, and postoperative improvement of pain is difficult to predict. The objectives of this study were to assess the surgery-related results obtained in patients who underwent treatment for syringomyelia associated with Chiari I malformation, particularly related to pain status, and to identify factors that may influence improvement in postoperative pain by comparing pre- and postoperative magnetic resonance (MR) imaging findings.

Methods. The correlation between pre- and postoperative changes in the size and the location of the syrinx and pain improvement was investigated in 25 patients. The shapes of the syringes were classified into three types: central, enlarged, and deviated. In most cases in which the syrinx deviated toward the posterolateral aspect of the spinal cord at the level corresponding to dermatomal distribution of preoperative pain, the lesion remained at the same position postoperatively, and improvement in pain was poor. On the other hand, enlarged-type syringes were the most frequently observed prior to surgery, exhibited diverse changes postoperatively, and improvement in pain status was difficult to predict. When postoperative MR imaging revealed a transformation to the deviated type, poor pain improvement was noted.

Conclusions. Neurons in the dorsal horn were thought to be involved in the development of pain as a result of the deafferentiation mechanism in cases of syringomyelia.

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Yuto Ogawa, Yoshiaki Toyama, Kazuhiro Chiba, Morio Matsumoto, Masaya Nakamura, Hironari Takaishi, Hisashi Hirabayashi and Kiyoshi Hirabayashi

Object. Numerous surgical procedures have been developed for treatment of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine, and these can be performed via three approaches: anterior, posterior, or combined anterior—posterior. The optimal approach in cases involving OPLL-induced cervical myelopathy, however, remains controversial. To address this issue, the authors assessed the benefits and limitations of expansive open-door laminoplasty for OPLL-related myelopathy by evaluating mid- and long-term clinical results.

Methods. Clinical results obtained in 72 patients who underwent expansive open-door laminoplasty between 1983 and 1997 and who were followed for at least 5 years were assessed using the Japanese Orthopaedic Association (JOA) scoring system. The mean preoperative JOA score was 9.2 ± 0.4; at 3 years postoperatively, the JOA score was 14.2 ± 0.3 and the recovery rate (calculated using the Hirabayashi method) was 63.1 ± 4.5%, both having reached their highest level. These favorable results were maintained up to 5 years after surgery. An increase in cervical myelopathy due to progression of the ossified ligament was observed in only two of 30 patients who could be followed for more than 10 years. Severe surgery-related complications were not observed. Preoperative JOA score, age at the time of surgery, and duration between onset of initial symptoms and surgery affected clinical results.

Conclusions. Mid-term and long-term results of expansive open-door laminoplasty were satisfactory. Considering factors that affected surgical results, early surgery is recommended for OPLL of the cervical spine.

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Morio Matsumoto, Kazuhiro Chiba, Masaya Nakamura, Yuto Ogawa, Yoshiaki Toyama and Jun Ogawa

Object. Structural interlaminar graft materials were used for atlantoaxial transarticular screw fixation (TSF), and its impact on the fusion status was investigated.

Methods. Forty-two patients (10 men, 32 women, mean age 51 years, mean follow-up period 45 months; 30 with rheumatoid arthritis, and 12 with os odontoideum) underwent TSF and modified Brooks posterior wiring involving titanium cables. As interlaminar graft materials, autologous bone from posterior iliac crest alone was used in 20 patients (Group A), and a structural spacer (13 ceramic spacers, nine titanium mesh cages) in 22 (Group B). Lateral radiographs were evaluated to determine bone fusion, alignment of the cervical spine, and wire loosening. Solid osseous fusion was obtained in 95% of Group A and 96% of Group B patients. The mean atlantoaxial angle was 19.1 ± 9.7° and 16.7 ± 10.4° before surgery (p = 0.45), and 27.4± 7.8° and 22.1 ± 5.5° after surgery (p = 0.02) in Groups A and B, respectively. Atlantoaxial hyperlordosis (atlantoaxial angle ≥ 30°) was observed in 32% of Group A and 18% of Group B patients (p = 0.26). Postoperative kyphosis occurred in 40% of Group A and 23% of Group B patients (p = 0.28). Loosening of the cable was demonstrated in 50% of Group A and 36% of Group B patients (p = 0.37). In Group B patients maintenance of cervical lordosis was more likely than in those in Group A, although the differences did not reach statistical significance.

Conclusions. These results indicate that structural interlaminar spacers can maintain proper cervical alignment without a decease in the fusion rate; the authors recommend their use in conjunction with TSF.