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Study Design: A clinicobiomechanical study., Objective: To clarify the clinicobiomechanical characteristics of a segment with lumbar degenerative spondylolisthesis (LDS) using an original intraoperative measurement system., Summary of Background Data: Although radiographical evaluation of LDS is extensively performed, the diagnosis of segmental instability remains controversial. The intraoperative measurement system used in this study is the first clinically available system that performs cyclic flexion-extension displacement of the segment with all ligamentous structures intact and can determine both the stiffness (N/mm) and neutral zone (NZ, [mm/N])., Methods: Forty-eight patients with LDS (males/females = 19/29, 68.5 yr; group D) were compared with 48 patients with lumbar spinal stenosis without LDS (males/females = 33/15, 64.8 yr, group N) in terms of symptoms, radiological, and biomechanical results. Instability was defined as a segment with NZ more than 2 mm. Symptoms (36-Item Short Form Health Survey), radiographical findings (radiographs, magnetic resonance images, computed tomographic scans), stiffness, NZ, and frequency of instability were also compared. Risk factors for instability were analyzed by multivariate logistic regression with a forward stepwise procedure., Results: None of the physical function categories or radiological findings of 36-Item Short Form Health Survey and low back pain (visual analogue scale) differed significantly between the groups. Although NZ was significantly greater in group D (1.97) than in group N (1.73) (P < 0.05), the frequency of instability did not differ significantly between groups. Facet opening (odds ratio, 11.0; P < 0.01) and facet type (odds ratio, 6.0; P < 0.05) were significant risk factors for instability., Conclusion: Neither the symptoms nor the frequency of instability differed significantly between groups. The radiological findings of spondylolisthesis did not indicate instability, but facet opening and sagittally oriented facets were indicative of instability. The results of this study demonstrated that LDS is not always unstable in the measurement setting, suggesting that the instability of LDS can stabilize spontaneously during the natural course., Level of Evidence: N/A.

Study Design: Retrospective clinical study., Objective: To evaluate clinical results of patients with nontraumatic cervical lesions treated by cervical pedicle screw (PS) fixation and to discuss the surgical indications., Summary of Background Data: PS fixation provides an outstanding stability for cervical lesions with instability. This technique, however, has a potential risk of vertebral artery, spinal cord, and nerve root injuries, which may be catastrophic., Methods: Fifty-eight patients were divided into 2 groups: patients with cervical kyphosis with vertebral destructive lesions (group D, n = 38) and those without destructive lesions (group ND, n = 20). Clinical results of the 2 groups were compared. The results of decompression and PS fixation for cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL) in this series were also compared with those of previous laminoplasty alone in patients with CSM and OPLL., Results: Nape pain in group D improved in 86.7% of the patients. Overall neurologic status was improved in both groups. Bony fusion was confirmed in 100% of the cases that were alive in group D and 95% in group ND. Eight complications including 2 vertebral artery injuries occurred. The incidence of postoperative cervical complications in group ND was significantly higher than that in group D. Although PS fixation significantly corrected cervical kyphosis and maintained in both CSM and OPLL, operation time and intraoperative blood loss in cases treated by PS were significantly higher than those treated by laminoplasty alone. Improvement of nape pain and neurologic status did not differ with and without using PS fixation., Conclusion: There is an indication of cervical PS fixation for destructive lesions because of a high fusion rate with improvement of nape pain. On the other hand, there is no indication in cases of typical CSM and OPLL if a potential risk of vertebral artery or nerve injury is taken into account.

Study Design: Retrospective analysis., Objective: To test the hypothesis that spinal cord lesions cause postoperative upper extremity palsy., Summary of Background Data: Postoperative paresis, so-called C5 palsy, of the upper extremities is a common complication of cervical surgery. Although there are several hypotheses regarding the etiology of C5 palsy, convincing evidence with a sufficient study population, statistical analysis, and clear radiographic images illustrating the nerve root impediment has not been presented. We hypothesized that the palsy is caused by spinal cord damage following the surgical decompression performed for chronic compressive cervical disorders., Methods: The study population comprised 857 patients with chronic cervical cord compressive lesions who underwent decompression surgery. Anterior decompression and fusion was performed in 424 cases, laminoplasty in 345 cases, and laminectomy in 88 cases. Neurologic characteristics of patients with postoperative upper extremity palsy were investigated. Relationships between the palsy, and patient sex, age, diagnosis, procedure, area of decompression, and preoperative Japanese Orthopaedic Association score were evaluated with a risk factor analysis. Radiographic examinations were performed for all palsy cases., Results: Postoperative upper extremity palsy occurred in 49 cases (5.7%). The common features of the palsy cases were solely chronic compressive spinal cord disorders and decompression surgery to the cord. There was no difference in the incidence of palsy among the procedures. Cervical segments beyond C5 were often disturbed with frequent multiple segment involvement. There was a tendency for spontaneous improvement of the palsy. Age, decompression area (anterior procedure), and diagnosis (ossification of the posterior longitudinal ligament) are the highest risk factors of the palsy., Conclusions: The results of the present study support our hypothesis that the etiology of the palsy is a transient disturbance of the spinal cord following a decompression procedure. It appears to be caused by reperfusion after decompression of a chronic compressive lesion of the cervical cord. We recommend that physicians inform patients and surgeons of the potential risk of a spinal cord deficit after cervical decompression surgery.

Study Design: Description of surgical technique and retrospective review of 13 cases., Objectives: To describe the surgical technique of margin-free spondylectomy and the outcome of 13 cases and to discuss the advantages and limitations of the procedure., Summary of Background Data: Recently, spondylectomy became a standard procedure by several pioneers. For extended malignant spine tumors involving pedicles or epidural space, however, performing an "en bloc" resection with a tumor-free margin remains a challenge., Methods: Our procedure consists of a combined anterior and posterior procedure with one or two stages. In the anterior procedure, tumor vertebrae are covered by the pleura or psoas muscles as a barrier. The posterior procedure includes decompression through the intact posterior elements, coverage of the tumor with all possible soft tissue barriers, and en bloc extirpation by rotating the tumor vertebrae around the spinal cord. We performed this procedure in 13 cases: 3 chondrosarcoma, 3 giant cell tumor, 1 osteosarcoma, 1 chordoma, and 5 metastases., Results: Neurologic status and pain improved in all cases except asymptomatic cases. There was no local recurrence, except in 2 cases (chondrosarcoma with extirpation of 5 vertebrae, chordoma with multiple previous surgeries). Two cases of chondrosarcoma were disease-free 14 years and 13 years after surgery, respectively., Conclusion: Although the best chance for a cure in extended malignant tumors of the spine is realized through wide resection, the procedure is not yet standardized. Margin-free spondylectomy is technically demanding, but the procedure can be used with a confidence as a more radical surgery for tumors extending to the epidural space and the unilateral pedicle. A key to success is the surgical technique, including a 360 degree dissection around the tumor vertebrae, instrumentation, and removal of the lesion with all possible soft tissues maintained intact to function as a barrier, like the dura mater.

Study Design: Two case reports of sciatica that was considered to be caused by cervical and thoracic spinal cord compression., Objectives: To point out that sciatica can be an initial major symptom in patients with cervical or thoracic spinal cord lesions., Summary of Background Data: Usually, tract pain caused by cord compression is considered to be diffuse and does not resemble sciatica., Methods: Medical history, physical findings, and the results of imaging studies were reviewed in one case of cervical cord tumor and one case of thoracic kyphosis., Results: In both cases, sciatica was the initial and major symptom. Imaging studies showed no lesion in the lumbar spine. In one patient, a cervical dumbbell tumor was found to compress the cervical cord, and in the other the spinal cord was severely compressed at the thoracic kyphosis. The sciatica disappeared immediately after decompression surgery in both cases., Conclusions: Leg pain resembling sciatica can be caused by cord compression at the cervical and thoracic level. Thoracic kyphosis may be a causative factor in sciatica, in addition to spinal cord tumor and disc herniation, which have been reported previously.

Study Design: This is a retrospective study of the morphologic limitations of posterior decompression for ossification of the posterior longitudinal ligament in the cervical spine., Objectives: To determine the morphologic limitations of the posterior approach in the management of ossification of the posterior longitudinal ligament., Summary of Background Data: Thirty-eight patients who underwent laminoplasty by midsagittal splitting for ossification of the posterior longitudinal ligament were reviewed. Fifteen patients were included in the noncontact group, in which the spinal cord was free of the ossified lesion after posterior decompression. Twenty-three patients were included in the contact group, in which the spinal cord was not free of the ossified lesion even after posterior decompression., Methods: The preoperative sagittal alignment of the cervical spine and preoperative maximal thickness of ossification were compared between the two groups. In addition, the morphologic limitations of posterior decompression for ossification of the posterior longitudinal ligament were investigated., Results: The following factors were found to contribute significantly to contact between the spinal cord and ossification of the posterior longitudinal ligament after posterior decompression: 1) lordosis of less than 10 degrees or kyphosis in the preoperative sagittal alignment, and 2) preoperative maximal thickness of ossification of more than 7 mm., Conclusions: Patients who exhibit significant risk factors for continued contact of the spinal cord should be morphologically considered for anterior decompression.

Study Design: Introduction of a new diagnostic procedure and a report on its usefulness., Objectives: To introduce a new endoscope (myeloscope) developed for the examination of the spinal canal and to present a previously unreported subarachnoid condition as a cause of paraparesis revealed by it., Summary of Background Data: In spite of the availability of advanced imaging technology, there still exists a significant number of patients with spinal diseases in whom a diagnosis cannot be made. Direct visualization of the pathologic area is required in these patients. Recent advances in fiberoptics have made this possible., Methods: The endoscope consisted of a fiberscope with an external diameter of 0.5, 0.9, or 1.4 mm. It was inserted into the subarachnoid space in the lumbar spine and carefully advanced cranially. Since 1987, this examination has been performed on 18 patients aged 7 to 69 years who had pain or other neurologic symptoms of unknown origin., Results: The surface of the spinal cord, roots, properties of the arachnoid membrane, and small vessels could be observed clearly. The scope could be advanced as far as the upper cervical spine. Cotton-candy-like proliferation of fibrous tissue was identified by myeloscopy in four paraparetic patients who had clinical and radiologic features similar to those of a spinal cord herniation. The fibrous tissue beat on the spinal cord with the pulsation of the spinal fluid. Resection of the fibrous tissue with conventional surgery resulted in neurologic improvement. Complications included one case of meningitis in the early period and five cases of postspinal headache. No nerve injury was apparent., Conclusions: Myeloscopy provides detailed information about the subarachnoid space and even reveals dynamic conditions that cannot be identified during open surgery or at autopsy. It will bring new concepts to the diagnosis of spinal diseases.

Study Design: Radiologic and operative findings of intravertebral cleft in the osteoporotic spine were investigated and the pathomechanism discussed., Objectives: To clarify the pathologic features of the intravertebral cleft., Summary of Background Data: Intravertebral "vacuum" cleft is one of the common radiographic findings in the osteoporotic spine. It is thought that the cleft is a rare lesion of an ununited fracture, or pseudarthrosis. Evidential findings of the disease, however, have never been reported., Methods: Simple bone grafting was performed in five cases (average age, 76.8 years) of thoracolumbar intravertebral cleft in osteoporotic spine in patients who had been suffering from prolonged pain of the back or leg. Preoperative radiologic evaluation using flexion-extension radiograph and magnetic resonance imaging was performed in all patients. At operation, the cleft and the components of the structure were macroscopically and microscopically observed. The fluid content in the cleft was biochemically analyzed., Results: In all patients, preoperative flexion-extension radiographs showed intravertebral instability at the location of the clefts that indicated gas density in three cases and water density in two cases. Magnetic resonance imaging showed that, for the most part, the cleft was low intensity on the T1-weighted image and high intensity on the T2-weighted scans, regardless of the radiographic findings. At operation, abnormal movement was observed at the cleft of the affected body, which was covered with hypertrophic membrane. The serous fluid within the cleft was aspirated before the excision of soft tissue. The thick membrane was excised and showed that the cleft was lined by smooth fibrocartilaginous tissue and the great degree of motion between the fracture ends that is consistent with the pathologic appearance of pseudarthrosis., Conclusions: The unstable cleft in the affected vertebral body of the osteoporotic spine with magnetic resonance findings of low intensity on the T1-weighted scans and high intensity on the T2-weighted scans suggests that the cleft is a false joint lined by fibrocartilaginous tissue with notable movement consistent with pseudarthrosis.

Study Design: Using helical computed tomography with three-dimensional and multiplanar reconstruction, ossification of the posterior longitudinal ligament in the cervical and thoracic region was observed. Preoperative simulation also was performed, and the availability of these methods was evaluated., Objective: To use preoperative evaluation and simulation with helical computed tomography to enhance the accuracy of excision of ossification of the posterior longitudinal ligament lesion., Summary of Background Data: Ossification of the posterior longitudinal ligament lesion is sometimes so complicated that preoperative morphologic evaluation and excision of the lesion are difficult when using only conventional imaging techniques., Methods: Seven cases of cervical and two cases of thoracic ossification of the posterior longitudinal ligament were scanned using helical computed tomography at 2-mm or 5-mm slice thickness. Three-dimensional and multiplanar reconstruction were performed at 0.7-mm or 2-mm intervals in the bone window. Surgical simulation of the anterior approach for cervical lesion and posterior approaches for thoracic lesion was performed., Results: Preoperative direct observation of the ossification of the posterior longitudinal ligament lesion was possible, and the complicated structures could be understood more easily than with other conventional methods. When surgical simulation was performed in the workstation, the ossification of the posterior longitudinal ligament lesion was removed sufficiently on arbitrarily reconstructed view in the spinal canal. When the viewpoint then was changed to the approaching side, the location and dimension of the removed area were determined. In all cases, surgical approach and excision of the ossification of the posterior longitudinal ligament lesion were performed more easily and more precisely than in the surgery with no three-dimensional images., Conclusion: Helical computed tomography with three-dimensional, multiplanar reconstruction would be a valuable tool for evaluation and surgical simulation of ossification of the posterior longitudinal ligament lesion by enhancing the accuracy of the surgical procedure.

Study Design: The reactions to sequestrated disc fragments, which were removed surgically from 35 patients, were examined histologically., Objectives: To elucidate whether or not there is histologic evidence of absorption of sequestrated discs., Summary of Background Data: Spontaneous disappearance or diminution of lumbar herniated discs in the spinal canal has been recognized, and this could be a possible explanation for relief of symptoms without surgery. The mechanism of this phenomenon is unclear., Methods: Sequestrated discs removed surgically from 35 patients were examined histologically., Results: In 30 cases, neovascularization was observed at the periphery of the sequestrated discs. Many foamy cells (macrophages) were present in the vascularized areas. In addition, immunohistochemistry revealed that many spindle-shaped, fibroblast-like cells were positive for CD68, a marker of macrophages. No fibrous scar formation was observed in any region., Conclusion: These findings suggest that organization is not a main course for this type of herniated disc and that a kind of "absorption" process occurs predominantly in the healing stage.

Two groups of patients with diseased lumbar spines treated by the Steffee variable screw placement system were studied, in order to compare concomitant posterolateral fusion and posterior lumbar interbody fusion. The use of posterolateral fusion resulted in less invasiveness than posterior lumbar interbody fusion, with regard to operating time and blood loss. With the posterolateral fusion method, correction of olisthesis or kyphotic deformity, if attained at all, was difficult to maintain. Posterior lumbar interbody fusion produced better correction and maintenance, even in osteoporotic cases. Bone union was achieved at an average of 11 months in only 60% of the posterolateral fusion group, whereas it was complete within a significantly shorter period (average; 6 months) in 91% of the posterior lumbar interbody fusion group. Breakage or loosening of screws occurred in 14% of the posterolateral fusion group. Deep wound infection and adhesive arachnoiditis, which were never seen in the posterolateral fusion group, developed in 3% of the posterior lumbar interbody fusion group. Posterior lumbar interbody fusion is considered to be a better method of bone grafting than posterolateral fusion, when used with the Steffee variable screw placement system.

Magnetic resonance imaging and histologic features of hypertrophic cervical posterior longitudinal ligament were determined in a cervical myelopathy patient. On T1-weighted images, the thickened ligament and the prolapsed nucleus pulposus showed isointensity shadows, making it impossible to differentiate these tissues. On T2-weighted images, the thickened ligament and prolapsed nucleus pulposus were visualized at high and low intensity, respectively. Sagittal T1-weighted images after gadolinium-diethylene triamine pentaacetic acid injection showed obvious enhancement of the thickened ligament.

To study the safety of hyperthermia cancer treatment, canine spinal cords were heated with radio waves to between 43 C and 47 C for 30 minutes. Spinal cord evoked potentials (SCEP) studied by epidural recording after epidural stimulation showed shortened latency and unchanged amplitude at 44 C or below. At 45 C or above, reduction of amplitude combined with shortened latency was observed, a phenomenon that has not hitherto been reported. After heating to 45 C, SCEP recovered with the reduction of temperature, but histologic examinations showed pigment exudation, vacuolation, and hemorrhage. These results suggest that tolerable spinal cord temperature should not exceed about 44 C.