Posterior cervical fixation using instrumentation is becoming a popular and useful method worldwide. There are many screw types and insertion techniques such as the Magerl screw, pedicle screw, lateral mass screw, subaxial transarticular screw, intralaminar screw and so forth. These rigid internal fixation methods produce a short segmental fixation. In this review, each indication for and the technical feasibility and safety of these screws are briefly described.

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This article is an overview the current status of navigation systems used in spinal surgery to emphasize their importance and to clarify the trend in which navigation technology is evolving. At this moment, there are three major latest-model navigation systems (S7 [Medtronic], Cart II [Stryker], and Kolibri [BrainLab]) used in Japan. Each system has its unique characteristics. It is essential to select the most suitable system based on the specific, differing needs of each hospital. Navigation assist is useful especially in transpedicular screw placement. The navigation unit is used for preoperative screw planning and it assures safety during its insertion. Therefore, it also offers a good spine surgery educational benefit. There are a couple of key points to safely use navigation systems. First a combination of fluoroscope and navigation is mandatory. Secondly, a reference frame should be established and remain untouched during the procedure. Recently, some new technologies have been invented to enable more precise navigation. Intraoperative acquisition of the source image is one such example. Also, robotic assist under navigation guidance for percutaneous pedicle screw placement has been introduced abroad. And in the future, a navigation technique based on the intraoperative functional image may become practical.

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Today, intraoperative neurophysiological monitoring (IOM) is standard practice in neurosurgery. Since spine surgery is a functional operation, the importance of IOM is especially high. By offering early detection of reversible neurophysiologic dysfunction during surgery, IOM allows prompt intervention and prevents the occurrence of permanent neurological damage. One of the most important roles of IOM is the promise of improving neurological outcome after surgery. Although IOM is performed in almost all cases of spinal cord tumors generally, it is not necessarily performed when treating degenerative diseases, which are also the most common disease. We are applying IOM to treatments for all of the degenerative diseases. Motor evoked potentials (MEP) and somatosensory evoked potentials (SEP) are used as basic methods and various other monitoring methods such as D-wave or direct stimulation are added according to the individual case requirements. Although direct stimulation of the cerebral cortex is the most stable method to record MEP, transcranial stimulation is generally used in spinal surgery. The transcranial MEP is a simple and useful method ; however, there are some problems that remain to be solved such as the ability to establish an alarm point overcoming the easy effect of muscle relaxants. Moreover, in order to monitor a waveform with a small potential like SEP, it is important to reduce artifacts generated from the operation apparatus. Aquiring such basic methods as MEP or SEP is essential for stable IOM. In this paper, we explain how standard IOM is deployed for spine surgery and multi-channel monitoring for complicated cases.

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OBJECTIVE : The purpose of this study was to evaluate radiological and clinical results in patients with lumbar spinal canal stenosis due to degenerative spondylolisthesis who had undergone posterior decompressive surgery without fusion. We report our findings in 31 patients who were followed for at least 3 years after surgery. PATIENTS AND METHODS : We evaluated 31 consecutive patients who underwent posterior decompressive surgery without fusion between 2001 and 2005. The mean follow-up period was 62.3 months. Clinical results were evaluated using the Japanese Orthopaedic Association (JOA) score and the recovery rate. The radiographic parameters we assessed were the change in % slip and the slip angle on lateral neutral films, and translation and dynamic angulation on lateral flexion and extension films obtained before and after surgery. RESULTS : The symptom recovery rate assessed with the JOA scoring system was 76.6%. There was no statistically significant difference between pre- and postoperative measurements with respect to the slip angle, translation, and dynamic angulation. The postoperative % slip was statistically larger than the preoperative value (p<0.01) although the progression of slippage and instability after surgery did not affect the clinical results. We performed reoperation in 2 patients (6.5%) ; they underwent posterior decompression. None of the 31 patients required secondary fusion. Six patients had sacroiliac joint syndrome after surgery, and one patient had adjacent disorder. CONCLUSION : In the mid-term we obtained good operative results in patients who had undergone decompression without fusion to treat lumbar spinal canal stenosis due to degenerative spondylolisthesis. Our findings suggest that posterior decompression wide enough to reach the lateral recesses that avoids damage to the articular processes does not routinelv reauire spinal fusion and provides satisfactorv clinical results.

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Introduction: We usually perform the decompression surgery for lumbar degenerative spondylosis alone ; however, in cases of lumbar instability, lumbar degenerative spondylolisthesis and lumbar foraminal stenosis, posterior fusion surgery may also be selected. We have performed mini-open TLIF as a minimally invasive spinal surgery since 2006. We discuss our surgical method and operative results mainly concerning spinal column function. Materials and Methods: We have operated on 64 cases of lumbar degenerative disease by mini-open TLIF. In this procedure, the skin is linearly incised about 6 cm long. The neural decompression is performed via hemi-fenestration. A unilateral inferior facetectomy at the open side is performed and intervertebral fusion via the intervertebral foramen is achieved. At the contralateral side, the pedicle screws are inserted by an intramuscular approach between the multifidus muscle and longissimus muscle. We evaluated the clinical results and postoperative spinal column function. Results: The affected vertebral height increases significantly just after the operation ; however, correction loss was seen one year after the operation. The correction of slippage and lordosis between the affected vertebrae was maintained one year after the operation. As to the total balance of the spine, the postoperative C7 plumb line tended to move posteriorly, which meant an improvement in spinal sagittal balance. Discussion and Conclusion: The importance of spinal balance has recently been discussed. Spinal deformity such as severe kyphosis of the total spine may induce a restricted daily life and leas to a poor prognosis by respiratory and gastrointestinal problems. Finally, since we have selected short-segmental fusion, which must be inspected in the points of total spinal balance in the future.

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Object: The ligamentum flavum associated with hemorrhage was studied pathologically and immunohistochemically with special reference to subacute inflammation in order to reveal the mechanisms behind ligament degeneration. Materials and Methods: A 68-year-old man had suffered from pain in the right buttock and thigh for 4 months. L4-5 ganglion cyst compressing the L5 nerve root was revealed by MRI and microscopic ligamentectomy was performed. The specimen was pathologically stained with HE, EVG, AZAN, Congo red and immunohistochemically examined with CD31, CD34, VEGFR2, and vWF. The relationship between micro angiogenesis and grade of degeneration and inflamation in the ligaments was studied. Results: The ganglion cyst, originating from the facet joint, was associated with hemorrhage and inflammation and neovascularization were found around the ganglion. The angiogenesis was distributed from the inflammation area towards the ventral side membrane of the interlaminar ligament. The angiogenesis was observed in a far site from the inflammation and the CD34 positive stromal cells increased as the distance from the ganglion cyst increased. Discussion: The ganglion cyst induced inflammation and angiogenesis. We suspect that these new vessels were stretched and injured with the elastic ligament movement. And this mechanical stressed new vasculature origin bleeding formed the hematoma. Our findings suggest that the CD34 positive stromal cells have potential to respond to the angiogenesis. Conclusion: In our specimen, the inflammation-induced angiogenesis was suspected to cause the bleeding in the ganglion cyst.

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We report three cases of scalp rupture after cranioplasty using titanium plates. Case 1 is a 68-year-old man. Under the diagnosis of intracerebral hemorrhage, hematoma evacuation under endscope followed by a ventriculoperitoneal shunt was performed. Two years after the surgical intervention, his titanium plate became exposed from under the scalp. The titanium plate was removed and replaced with a bioabsorbable polymer. Case 2 is a 74-year-old female, who had surgery for a subarachnoid hemorrhage. Eleven years after the initial surgical intervention, removal of sequestrum and cranioplasty with titanium mesh was performed for her late-onset surgical site infection. After this surgical intervention, the mesh has become clearly visible through progressive skin thinning. Case 3 is a 65-year-old female, who underwent surgery for a subarachnoid hemorrhage. Six years after the surgery, the titanium plate which had been used for craniplasty at the initial surgery became exposed. Removal of the plate and scalp plasty to smooth the focally sharpened skull were performed. Scalp ruptures are usually caused by chronic stimulus caused by the titanium plate, incisional fragility of the scalp and subsidence of the scalp into the skull defect. Using a titanium plate on a curved or defected portion of the skull may also cause scalp rupture. We consider that bioabsorbable polymer may be useful to avoid these post-surgical cosmetic complications, especially in cases with these risk factors for scalp rupture.

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Hypoglossal schwannomas are extremely rare tumors and are usually associated with hypoglossal dysfunction. We report a case of intracranial hypoglossal schwannoma without hypoglossal nerve paresis in a 71-year-old woman. The patient experienced headache ; computed tomography (CT) and magnetic resonance imaging revealed a cystic mass on the right side of the medulla and cerebellum. The axial CT scan, at the bone window level, showed an enlargement of the right hypoglossal canal. The size of the tumor gradually increased during the 2-year follow-up. The patient was admitted to our hospital for surgical resection of the tumor. Neurological examinations yielded unremarkable findings. Since the patient was quite old, we resected the tumor via the right lateral suboccipital approach without exposing the hypoglossal canal. The entire tumor except the intracanalicular portion was excised. After tumor resection, normal rootlets and a trunk of the hypoglossal nerve were observed. The postoperative course was uneventful, and the patient showed no hypoglossal nerve paresis. In case of hypoglossal schwannoma without hypoglossal nerve paresis, an intact trunk of the hypoglossal nerve should be identified and retained during the operation to avoid hypoglossal dysfunction. Furthermore, since complete resection of the tumor frequently leads to the development of hypoglossal nerve paresis, deliberate incomplete resection is a therapeutic option, especially in elderly patients.

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