Cervical interbody fusion cages (CIFC) are currently used for anterior cervical fusion. There are few reports documenting their biomechanical property in the cervical spine. The purpose of the present study is to investigate biomechanical stability of the caprine cervical spine implanted with a CIFC device. Thirty-two spinal units (C3-4 and C5-6) were harvested from 16 fresh-frozen caprine cervical spines. Each spinal unit underwent discectomy and transection of the posterior longitudinal ligament, and then was implanted with single CIFCs, double CIFCs, autograft, or autograft and anterior cervical plate. An iliac crest tricortical bone was used as an autograft. The degrees of displacement of the cervical spine specimens by multidirectional moments in flexion, extension, lateral bending and axial rotation were evaluated using a video-recording. The stiffness against the multidirectional loads was calculated from load-displacement curves. There were no statistical differences in stiffness between the single-cage and autograft groups in flexion, extension and axial rotation. The autograft group showed significantly increased stiffness compared with that of the single-cage group in lateral bending. The stiffness values were far larger in both the double-cage and autogtraft with plating groups than in the other groups in all directions. There were no statistical differences in stiffness between the double-cage and autogtraft with plating groups in flexion, lateral bending and axial rotation. The double-cage group showed significantly decreased stiffness compared with that of the autograft with plating group only in extension. The stiffness values of the single- or double-cage groups would represent the characteristic biomechanical properties derived from the structure and shape of the implants.

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Anterolateral partial vertebrectomy, a new operative technique which involves drilling into the anterolateral part of the vertebral bodies, enables radical resection of the lesion, without any fusion. The cervical spine, however, could possibly become instable because of excessive resection to get a wider operative field. The authors describe the operative technique and emphasize that the approach should be made as laterally as possible to preserve postoperative vertebral stability. The patient is placed in a supine position, with the head in slight extension and rotation to the contralateral side. Supporting pads are placed at the contralateral side, providing for contralateral rotation of the operative table. Longus colli muscles are exposed through the routine anteromedial approach. The medial half of the ipsilateral longus colli muscle is excised for as many levels as required, and the lateral half is dissected from the vertebral bodies and reflected laterally with strings to expose the lateral wall of the vertebral bodies. The drilling is started at the anterolateral aspect of the vertebral bodies within the dissected area of the longus colli muscle. The drilling is extended obliquely toward the opposite side. The osteophytes or the ossification of the posterior longitudinal ligament are resected and the vertebral canal is opened widely, thus preserving more than half of the vertebral bodies. Postoperatively, all patients are asked to wear a soft collar for 4 weeks. The surgery was performed in 16 cases. The duration of postoperative follow-up ranged from 3 to 15 months, with an average period of 12 months. All of them except two improved neurologically. The cervical alignment was preserved in all patients.

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There are various methods of grafting for anterior cervical fusion. The most important thing for spinal fusion is to achieve decompression of the neural structure, reconstruction of stability, and physiological alignment of the cervical spine. Anterior cervical fusion with hydroxyapatite graft is gaining popularity in the management of degenerative cervical spine disease because this material has excellent bioactivity and biocompatibility, and makes it possible for patients to avoid the donor site problem. We have used three types of hydroxyapatite graft in 72 cases in the past 4 years. The underlying primary pathological conditions included disc extrusion, spondylosis, ossification and/or hypertrophy of the posterior longitudinal ligament, and epiphyseal dysplasia. No neurological deterioration related to the surgical procedure has been encountered. However, dislocation and collapse of the graft occurred in three patients who needed reoperation. Dislocation occurred in two patients who could not remain at rest after surgery, and we think it was caused because we did not make the embankment on the posterior portion of their vertebral bodies. Collapse occurred in one patient due to the fragility of the porous hydroxyapatite material with 42% porosity. Since then, we have used denser hydroxyapatite graft and have never experienced collapse of the graft. We would like to say that anterior cervical fusion with hydroxyapatite graft is one of the useful procedures for keeping good and precise fusion without donor site problem. Moreover, we intend to continue to follow up long-term postoperative results and to make efforts to devise the best procedure for patients.

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A new laminoplasty of the cervical spine has been developed using a newly designed hydroxyapatite spacer for laminae which are open en bloc bilaterally. The trapezoidal shaped spacer, designed to fit the contour and section of the lamina, was placed on both sides of each lamina, which was anchored by titanium miniplate to the lateral mass bilaterally. We have used this method in 10 patients with cervical spondylosis and 6 patients with ossification of the posterior longitudinal ligament for expansive laminoplasty, and 4 patients with spinal tumors. The rigid fixation of laminas allowed less restricted postoperative care including a few days application of a simple neck collar. There was no postoperative complication associated with lanimoplasty. The new method, maintaining the spinolaminoligamentous complex intact, contributed to the reduction of operative time and complications sometimes found in unrigid laminoplasty. This method is compatible with laminoplasty after removal of an intracanalicular mass and for decompression surgery for canal stenosis.

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We investigated 16 surgically treated cervical central spinal cord injury patients (10 males and 6 females) without bony injury. Age at injury varied from 24 to 84 (mean, 60.3 years). Magnetic resonance (MR) imaging disclosed spinal cord compression in all patients. Dynamic cervical lateral X-ray showed mild to moderate instability in 11 patients. Fourteen patients who had been admitted within 8 hours after the injury were treated with high-dose methylpredonisolone. Interval between injury and surgery ranged from 1 to 35 (mean, 8.6) days. Patients with a single or two-level segmental cord compression underwent anterior decompression and fusion while patients with multi-level cord compression underwent posterior decompression and fusion. Postoperatively, all patients showed neurological improvement of one to two grades on Frankel's scale. Our results demonstrated that the relatively early surgical intervention will be mandatory for the patients with cervical central spinal cord injury with instability and cord compression.

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We installed an intraoperative computed tomography (CT) imaging system using a self-moving helical CT scanner gantry enabling intraoperative three dimensional (3D) imaging in the operating room, and used this system to assist in cervical spine surgery. Intraoperative CT scanning with this system was performed in 47 patients with cervical spine diseases including cervical spondylosis in 22 cases, ossification of the posterior longitudinal ligament (OPLL) in 14 cases, cervical intervertebral disc herniation in 8 cases, cervical spine injury in 2 cases, and meningioma in the cervical spinal canal in 1 case. It takes only about 15 minutes for intraoperative CT scanning while the surgical wound remains open, the surgical drapes are kept in place, and the surgical position remains unchanged. We were given enough working space while doing surgery by placing the CT gantry away from the operating table. Self-moving helical CT scanner gantry enabled scanograms, which made it possible to decide accurately the extent of the scanning even after draping of the patient's neck. It also enabled intraoperative 3D imaging of the cervical spine, which was useful especially for determination of the extent of vertebrectomy and detection of residual bony lesions such as osteophyte and OPLL, permitting further surgery when needed. We were able to carry out more complete and safe cervical spine surgery by using this intraoperative CT imaging system.

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Since the development of MRI techniques, congestive myelopathy has been revealed to be an important clinical entity. We report here 10 cases of congestive myelopathy and discuss the surgical indication. In the last 10 years, we have encountered 199 cases of spinal disease, among which there were 10 cases of congestive myelopathy. Five out of 9 cases of spinal dural AVF, 4 out of 19 cases of spinal AVM, and 1 out of 1 case of arachnoiditis showed congestive myelopathy secondarily. All patients underwent surgical and/or endovascular procedures and all but one showed clinical improvement. We recommend surgery for congestive myelopathy before it progresses to myelomalacia. Especially in the case of congestive myelopathy due to spinal AVF, surgery should be the first choice.

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The purpose of this study is to evaluate safety, fusion, and clinical outcome of posterior lumbar interbody fusion (PLIF) for spondylolisthesis. There were 38 patients who underwent PLIF in our department, of whom 18 were males and 20 were females, with ages ranging from 35 years to 79 years (mean : 55 years). Thirty-four patients had severe low back pain, 17 had neurogenic intermittent claudication, and 15 had numbness and weakness of the lower extremities. Seven patients had isthmic spondylolisthesis (grade 1), and 31 had degenerative spondylolisthesis (grade 1). Posterior decompression and fusion with interbody cages were carried out in all cases. Six patients received an additional pedicle screw fixation. Postoperative pain relief and gait improvement were achieved in 33 patients (87%) with the degree of "excellent" in 22 (58%), "good" in 11 (29%), and "fair" in 5 (13%). Postoperative X-rays disclosed good segmental fusion without halo around cages or abnormal segmental motion in 90.3% (28/31). There were 2 cases of cerebrospinal fluid leakage, 3 of superficial wound infection, and 3 of cage dislocation. Posterior lumbar interbody fusion showed a safe and effective procedure for both low grade isthmic and degenerative spondylolisthesis.

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Objective : Spinal dural arteriovenous fistulas (AVFs) represent a rare but important cause of myelopathy brought about by venous hypertension due to shunt formation between the dural artery and medullary vein. Magnetic resonance imaging (MRI) findings include intramedullary hyperintensity on T2-weighted images, as well as cord enlargement due to venous hypertension. Postoperative resolution patterns of hyperintensity suggest a pathophysiology of spinal dural AVF. Clinical presentation and results : We report two cases of thoracic spinal dural AVF with a single feeding artery, which were treated by surgical intervention. MRI findings were reviewed before and after surgery. Before surgery, hyperintensity on T2-weighted images spread from above the feeding artery to the conus, and was present in the central cord on axial images. After correction of the arteriovenous shunt, the region of hyperintensity began to resolve from the cranial side followed by the caudal side. Conclusion : Hyperintensity on T2-weighted images of the cord was largely reversible, indicating that edema of the cord was caused by elevated venous pressure. The hyperintensity on T2-weighted images decreased initially from the cranial side and then from the caudal side. This transmission and resolution of increased venous pressure appeared to depend on the presence of obstruction to the venous outflow system of the spinal cord.

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Thoracic disc herniations are relatively rare disease. In particular, dorsally herniated thoracic discs are even more infrequent. We report a 70-year-old man who presented with a three weeks' history of paraparesis which was caused by a dorsal disc herniation. Magnetic resonance imaging demonstrated a limb-enhanced intraspinal mass with a "tent-like" round configuration at T11-12 intervertebral level. His symptoms improved after removal of the herniated disc material through the posterior approach. Laminectomy combined with the partial removal of the facet joint was appropriate in this case.

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