Published papers

The structural changes of apatite ceramics with bioactive function and mechanical property in in vivo and in vitro were investigated. For starting materials for making HA ceramics, submicrometer HA ceramics powder was used, and pressureless sintering was performed at 1573K in O2 atmosphere using pre-sintered bodies. Fracture resistance tests were performed using compact tension specimens, whose configuration was the tension test piece into which a notch of 16mm long was introduced. The results showed improvement of fracture resistance in simulated body fluids (SBF) environment, and maintenance of fracture resistance was also shown in rat abdomen subcutis.

The expression levels of osteoblast differentiation markers and the effect of geometry of porous hydroxyapatite (HAp) fiber scaffold on the differentiation were investigated. The glyceraldehyde-3-phosphate dehydrogenases (GAPDH) mRNA was used as internal control to estimate expression level of differential marker mRNA. An apparent acceleration of the expression was observed for osteoblast differentiation in induced condition. The results show that the materials with various pore sizes effects the three-dimensional apatite fiber scaffold on cell profileration and differentiation.

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.

Marfanoid habitus suggests abnormal microfibril formation, whereas a situs ambiguus or situs inversus phenotype points to detective left-right axis determination. The concurrence of these two abnormalities has been reported only once in the literature. We report a similar phenotype in two unrelated patients. Documentation of this specific combination of Marfanoid habitus and abnormal situs gives further credence to the notion that the combination may represent a distinct syndrome. © 2004 Wiley-Liss, Inc.

Objective: We sought to determine factors likely to influence postoperative changes in cervical spinal curvature and range of motion (ROM) in patients with cervical spinal cord tumors. Methods: Fifty-one patients who underwent tumor excision via a single posterior approach were examined. Surgical methods were classified as follows: group A, expansive open-door laminoplasty (ELAP); group B, conventional laminectomy; and group C, hemilaminectomy (HL). Pre- and postoperative cervical spinal curvature, cervical curvature type, and ROM were evaluated using lateral radiographs. Results: Worsening of cervical curvature type was statistically less frequent in group C than in group A or B (P < 0.05), although no significant difference was evident overall between pre- and postoperative cervical curvature indexes or ROM in any group. Cases of C2 surgery showed more frequent curvature worsening (80%) in group A than in other groups (P < 0.05). Postoperative changes of the cervical curvature in patients with cervical spinal cord tumors were greatly influenced by the surgical method; the cervical curvature was particularly unfavorable when patients had C2 decompression. Conclusions: Careful attention to postoperative changes in the spinal curvature is needed when ELAP is performed, especially if surgery involves C2. HL is the best posterior approach for resection of cervical spinal cord tumors from the viewpoint of postoperative spinal curvature and ROM.

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.

HAp films with good adhesive property were formed by a simple surface treatment utilizing an enzyme reaction of urea with urease. The resulting coating layer consisted of carbonate-containing HAp with poor crystallinity. The in vitro evaluation using osteoblastic cells showed that HAp-coated Ti substrate had a good cellular response, such as cell proliferation and differentiation into osteoblast. From the results of in vivo evaluation using rabbit models, the HAp-coated Ti substrate directly bonded to bones to form large amount of new bone around implant. It has been found from both the in vitro and in vivo evaluations that the present HAp-coated Ti substrate has excellent biocompatibility.

Novel scaffolds have been developed from single-crystal apatite fibres synthesized by a homogeneous precipitation method using urea. The resulting apatite fibre scaffolds have large pores with diameters of 110-250 μm and high porosities of 98-99%. The scaffolds were biologically evaluated using two kinds of cells, osteoblast cells (MC3T3-E1) and rat bone marrow cells. In both cases, the cells cultured in the scaffolds showed excellent cellular response, such as good cell proliferation and enhanced differentiation into osteoblasts. We conclude that such scaffolds with high porosity and large pore size may be effective as the matrix of tissue engineered structures in order to promote regeneration of bone.

Background context: Threaded cage technology has had a meteoric rise in usage. It has been touted as a procedure with low risk and minimal complications. PURPOSE: To gauge the spine surgical community's general consensus regarding cage usage and its complications. Study design/setting: A canvassing questionnaire regarding threaded cage usage and complications was sent to members of the North American Spine Society. Patient sample: A total of 665 doctors reported on their perception of 22,585 cages placed by the second year after pre-market approval from the Food and Drug Administration approval. Outcome measures: A nonscientific canvassing questionnaire was thought to give a consensus of surgical outcome perception in a large number of caregivers with hopes of understanding general trends. Methods: Simple statistical measurements were used to report perceived complications by surgeons involved in performing threaded cage surgical procedures. Results: Sixty-nine percent of doctors reported at least one complication with threaded cages, but the complication incidence was low. Visceral injuries were reported in 0.1%; vascular injuries, 1.0%; cage displacement and dislodgement, 1.4%; temporary and permanent neurologic injuries, 2.25% and 0.56%, respectively; infection 0.34%; retrograde ejaculation 1.2% and revision surgery recorded for 2.7%. Those rating cages as fair to poor (16.5%) were those physicians reporting the longest experience with this technology. Conclusions: The general consensus is that threaded cages have low complication rates and high satisfaction rates, 83.5%. The data represent a convenience sampling and is not scientific. © 2003 Elsevier Inc. All rights reserved.

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

Study design: Prospective study on magnetic resonance imaging (MRI) and radiographic findings of the cervical spine. Objective: To elucidate the age-related changes of the cervical spinal cord and the cervical spinal canal and the relationship between the spinal cord and the spinal canal in asymptomatic subjects using MRI and radiography. Setting: Tokyo, Japan. Methods: The transverse area of the cervical spinal cord and the ratio of the anteroposterior diameter to the transverse diameter (RAPT) were investigated, using MRI in 229 asymptomatic subjects. The sagittal spinal canal diameter and anteroposterior diameter of the cervical vertebral body were also measured on plain lateral radiographs. The canal body ratio (CBR), which was defined as the diameter of the spinal canal divided by that of the vertebral body, was calculated. Results: The transverse spinal cord area correlated negatively with age. RAPT did not correlate with age. The CBR correlated negatively with age. The correlation between spinal cord area and CBR was significant but weak and the correlation between RAPT and CBR was not significant. Conclusion: The transverse area of the cervical spinal cord measured by MRI decreased with age, while RAPT remained unchanged. The bony spinal canal became narrower with age. The spinal cord area and the shapes of the spinal cord were independent from the spinal canal diameter in asymptomatic subjects. These facts should be considered when evaluating radiological findings in patients with cervical spinal disorders.