Epidemiology and Comparative Analysis of Outcomes of Intramedullary Spinal Cord Tumor Between Pediatric and Adult Patients.

STUDY DESIGN: This was as clinical retrospective study. OBJECTIVES: We sought to evaluate the characteristics of Pediatric intramedullary spinal cord tumors (PISCTs) and to identify differences between pediatric and adult intramedullary spinal cord tumors. SUMMARY OF BACKGROUND DATA: PISCTs represent a rare clinical entity with limited evidence-base in the literature. METHODS: This study is a subanalysis of the retrospective multicenter observational study authorized by the Neurospinal Society of Japan, including consecutive patients with spinal intramedullary tumors treated surgically at 58 institutions between 2009 and 2020. Data on 1080 intramedullary spinal cord tumors were obtained, consisting of 91 pediatric and 939 adult patients. Survival was compared using Cox hazard regression while clinical differences were evaluated using multivariable logistic regression that controlled for confounders. RESULTS: Pediatric patients had a shorter overall, and progression-free, survival than adults. Pediatric patients with ISCTs were likely to have scoliosis [odds ratio (OR) = 6.49, 95% CI: 2.26-18.7], short preoperative symptom duration (OR = 0.99, 95% CI: 0.98-0.99), lower incidence of paresthesia (OR = 0.41, 95% CI: 0.22-0.77), higher incidence of paresis (OR = 2.10, 95% CI: 1.01-4.35), histopathology of astrocytoma (OR = 2.97, 95% CI: 1.19-7.43), and postoperative functional deterioration upon discharge (OR = 2.83, 95% CI: 1.43-5.58). Age was not a statistically significant prognostic factor of overall survival among the pediatric cohort. CONCLUSION: We found that the clinical characteristics of ISCTs differed between pediatric and adult patients. In terms of histopathological types, astrocytoma was most common in pediatric patients. ISCT occurring at an early age may not be an indicator for poor prognosis.

Impact of surgical treatment for intramedullary spinal cord metastasis on neurological function and survival: A multicenter retrospective study by the Neurospinal Society of Japan.

BACKGROUND: This retrospective multicenter study aimed to analyze the characteristics and surgical outcomes of intramedullary spinal cord metastasis (ISCM) and to discuss the controversy regarding its surgical indications. METHODS: This study included 29 ISCM patients who underwent surgery between 2009 and 2020. Biopsy cases were excluded from analysis. For functional and neurological functional assessments, Karnofsky Performance Status (KPS, %) and modified McCormick Scale (MMS, 5-grade scale) scores were determined before and after surgery. Patients were divided into two groups: a mild-to-moderate disability group with preoperative MMS grades 1 to 3, and a severe disability group with preoperative MMS grades 4 to 5. RESULTS: The mean preoperative KPS was 45.9, and the mean duration from symptom onset to surgical intervention was 1 month. The ISCM was located in the cervical spine in 10 cases and the thoracic spine in 19 cases. The access route (myelotomy) for ISCM removal was via the posterior median sulcus in 9 cases and via the posterior lateral sulcus in 11 cases, while others were not recorded. The degree of removal was gross total resection in 20 patients (69%), subtotal resection in 0 patients, and partial removal in 9 patients (31%). No significant complications related to the surgical procedures were recorded. Postoperative adjuvant therapy included radiotherapy in 17 patients (58.6%) and chemotherapy or molecular targeted therapy in 13 patients (44.8%). Pathological findings of ISCM showed that colorectal cancer was the most common in 9 cases, followed by lung cancer in 7, renal cell carcinoma in 5, and breast cancer in 2. Twenty-one of the 29 patients (72.4%) were confirmed to have survived 6 months after surgery: 8 of the 10 patients (80%) in the mild-to-moderate disability group and 13 of the 19 patients (68.4%) in the severe disability group. At 6 months after surgery, 3 of the 8 patients (38%) in the mild-to-moderate group were able to maintain or improve their function. Eleven of the 13 patients (85%) in the severe disability group maintained their function despite being severely disabled. CONCLUSIONS: This study suggests that surgical treatment can maintain or improve neurological function in a limited number of patients with ISCM, although it had minimal impact on improving the survival rate after surgery.

Predictors of Progression-Free Survival in Patients With Spinal Intramedullary Ependymoma: A Multicenter Retrospective Study by the Neurospinal Society of Japan.

BACKGROUND AND OBJECTIVES: Ependymoma is the most common spinal intramedullary tumor. Although clinical outcomes have been described in the literature, most of the reports were based on limited numbers of cases or been confined to institutional experience. The objective of this study was to analyze more detailed characteristics of spinal intramedullary ependymoma (SIE) and provide clinical factors associated with progression-free survival (PFS). METHODS: This retrospective observational multicenter study included consecutive patients with SIE in the cervical or thoracic spine treated surgically at a total of 58 institutions between 2009 and 2020. The results of pathological diagnosis at each institute were confirmed, and patients with myxopapillary ependymoma, subependymoma, or unverified histopathology were strictly excluded from this study. Outcome measures included surgical data, surgery-related complications, postoperative systemic adverse events, postoperative adjuvant treatment, postoperative functional condition, and presence of recurrence. RESULTS: This study included 324 cases of World Health Organization grade II (96.4%) and 12 cases of World Health Organization grade III (3.6%). Gross total resection (GTR) was achieved in 76.5% of cases. Radiation therapy (RT) was applied after surgery in 16 cases (4.8%), all of which received local RT and 5 of which underwent chemotherapy in combination. Functional outcomes were significantly affected by preoperative neurological symptoms, tumor location, extent of tumor resection, and recurrence. Multivariate regression analysis suggested that limited extent of tumor resection or recurrence resulted in poor functional outcomes. Multiple comparisons among the groups undergoing GTR, subtotal resection and biopsy, or partial resection of the tumor showed that the probability of PFS differed significantly between GTR and other extents of resection. CONCLUSION: When GTR can be safely obtained in the surgery for SIE, functional maintenance and longer PFS can be expected.

Quantitative Gait Feature Assessment on Two-Dimensional Body Axis Projection Planes Converted from Three-Dimensional Coordinates Estimated with a Deep Learning Smartphone App.

To assess pathological gaits quantitatively, three-dimensional coordinates estimated with a deep learning model were converted into body axis plane projections. First, 15 healthy volunteers performed four gait patterns; that is, normal, shuffling, short-stepped, and wide-based gaits, with the Three-Dimensional Pose Tracker for Gait Test (TDPT-GT) application. Second, gaits of 47 patients with idiopathic normal pressure hydrocephalus (iNPH) and 92 healthy elderly individuals in the Takahata cohort were assessed with the TDPT-GT. Two-dimensional relative coordinates were calculated from the three-dimensional coordinates by projecting the sagittal, coronal, and axial planes. Indices of the two-dimensional relative coordinates associated with a pathological gait were comprehensively explored. The candidate indices for the shuffling gait were the angle range of the hip joint < 30° and relative vertical amplitude of the heel < 0.1 on the sagittal projection plane. For the short-stepped gait, the angle range of the knee joint < 45° on the sagittal projection plane was a candidate index. The candidate index for the wide-based gait was the leg outward shift > 0.1 on the axial projection plane. In conclusion, the two-dimensional coordinates on the body axis projection planes calculated from the 3D relative coordinates estimated by the TDPT-GT application enabled the quantification of pathological gait features.

Cervical ganglioneuroma arising from the dorsal root ganglion: illustrative case.

BACKGROUND: Ganglioneuroma is a benign and well-differentiated tumor derived from neural crest cells, which occurs infrequently, with most patients being female and adolescents. While predilection sites are the posterior mediastinum and retroperitoneal cavity, ganglioneuroma originating from the dorsal root ganglion is very rare. Here the authors report a case with C2 dorsal root ganglion-derived ganglioneuroma with some literature review. OBSERVATIONS: A 45-year-old male patient complained of persistent right-side throbbing occipital headache for more than a year. Magnetic resonance imaging (MRI) of the cervical spine revealed a dumbbell-shaped intradural extramedullary tumor from the C2 posterior surface of the odontoid to right C1-2 intervertebral foramen with high T2- and low T1-weighted signal intensities. The tumor displayed homogeneous contrast enhancement by MRI. The authors suspected schwannoma and performed a tumorectomy for both diagnosis and treatment purposes. Intraoperative findings showed that the tumor originated from the dorsal root ganglion, and pathological examination revealed ganglioneuroma. Immediately after the tumorectomy, the throbbing occipital headache disappeared and the patient was discharged from the hospital without major complications. LESSONS: Although ganglioneuroma derived from the dorsal root ganglion is very rare, a differential diagnosis of the ganglioneuroma should be made, when schwannoma is suspected.

Development of Smartphone Application for Markerless Three-Dimensional Motion Capture Based on Deep Learning Model.

To quantitatively assess pathological gait, we developed a novel smartphone application for full-body human motion tracking in real time from markerless video-based images using a smartphone monocular camera and deep learning. As training data for deep learning, the original three-dimensional (3D) dataset comprising more than 1 million captured images from the 3D motion of 90 humanoid characters and the two-dimensional dataset of COCO 2017 were prepared. The 3D heatmap offset data consisting of 28 × 28 × 28 blocks with three red-green-blue colors at the 24 key points of the entire body motion were learned using the convolutional neural network, modified ResNet34. At each key point, the hottest spot deviating from the center of the cell was learned using the tanh function. Our new iOS application could detect the relative tri-axial coordinates of the 24 whole-body key points centered on the navel in real time without any markers for motion capture. By using the relative coordinates, the 3D angles of the neck, lumbar, bilateral hip, knee, and ankle joints were estimated. Any human motion could be quantitatively and easily assessed using a new smartphone application named Three-Dimensional Pose Tracker for Gait Test (TDPT-GT) without any body markers or multipoint cameras.

Current Trends in the Surgical Management of Intramedullary Tumors: A Multicenter Study of 1,033 Patients by the Neurospinal Society of Japan.

OBJECTIVE: We performed a retrospective observational study to demonstrate the surgical risks and long-term prognoses of intramedullary tumors in Japan using a multicenter registry authorized by the Neurospinal Society of Japan. METHODS: Data from 1,033 consecutive patients with intramedullary tumors, treated between 2009 and 2020, were collected from 58 centers. Patients with spinal lipomas or myxopapillary ependymomas were excluded. Patient characteristics, clinical presentations, imaging characteristics, treatments, and outcomes were analyzed. The modified McCormick scale was used to classify functional status. Survival was described using Kaplan-Meier curves, and multivariable logistic regression analyses were performed. RESULTS: The mean age of the patients was 48.4 years. Data of 361 ependymomas, 196 hemangioblastomas, 168 astrocytic tumors, 160 cavernous malformations, and the remaining 126 cases including subependymomas, metastases, schwannomas, capillary hemangiomas, and intravascular B-cell lymphomas were analyzed. Twenty-two patients were undiagnosed. The mean follow-up duration was 46.1 ± 38.5 months. Gross total tumor removal was achieved in 672 tumors (65.1%). On the modified McCormick scale, 234 patients (22.7%) had worse postoperative grades at the time of discharge. However, neurological status gradually improved. At 6 months postoperatively, 251 (27.5%), 500 (54.9%), and 160 patients (17.6%) had improved, unchanged, and worsened grades, respectively. Preoperative functional status, gross total tumor removal, and histopathological type were significantly associated with mortality and functional outcomes. CONCLUSION: Our findings demonstrate better postoperative functional outcomes in patients with fewer preoperative neurological deficits. Degree of resection, postoperative treatments, and prognoses are closely related to the histology of intramedullary tumors.

Description of the Diversity in Surgical Indication and Surgical Strategies for Primary Spinal Cord Tumors: A Nationwide Survey by the Neurospinal Society of Japan.

OBJECTIVE: To assess the current management of primary spinal cord tumors (PSCTs) and determine whether and to what extent there are differences in surgical strategies for PSCTs. METHODS: The Neurospinal Society of Japan conducted a survey between April 1 and 30, 2021. Certified spine surgeons were requested for information on the frequency of surgeries in 2020 and the surgical strategies adopted for each PSCTs. The following tumor histologies were focused: schwannoma, meningioma, and cauda equina tumor as extramedullary tumors; and ependymoma, hemangioblastoma, astrocytoma, and cavernoma as intramedullary tumors. The participants were divided according to their response as follows: experts, who had experienced ≥ 100 surgeries for PSCTs, and nonexperts. RESULTS: Among 308 participants (63%), 35 (11%) were experts. The total number of PSCTs in 2020 was 802 of which 564 tumors were extramedullary and 223 were intramedullary. Schwannoma accounted for 53% of the extramedullary tumors, and ependymoma accounted for 39% of the intramedullary tumors. Surgical strategies significantly differed among both the experts and nonexperts groups. Some discrepancies in the adopted surgical strategies were observed between groups. Some of the nonexperts, and none of the experts, ruled out surgery for schwannomas (Eden type 4), astrocytomas, or cavernomas. Five nonexperts (2.2%), and none of the experts, resected the entire dura for meningiomas. CONCLUSION: A nationwide survey revealed that a sufficient consensus did not exist regarding surgical strategies for PSCTs. A disease-specific registry for PSCTs is necessary in academic societies.

[Lumbar Interbody Fusion:How to Achieve Reliable Bone Fusion?]

The goal of surgery for degenerative spine disease is to decompress nerves; however, extensive spinal decompression may compromise spinal stability. Therefore, spinal fusion surgery is performed to immediately stabilize such anatomical disruption during a short hospital stay and to allow quick recuperation. Recently, implants such as pedicle screws and intervertebral cages have been regularly used in lumbar fusion surgery. These implants are used to reconstruct the functional unit of the failed spine, correcting any deformity if necessary and maintaining its fixation until complete bone fusion. In other words, the essence of spinal fusion surgery is not the placement of implants but the induction of bone fusion. Therefore, each case requires a carefully developed surgical plan to achieve sufficient bone fusion for spinal stabilization. In this article, we describe the mechanism and the surgical technique for achieving reliable interbody fusion.

A Case of Spinal Ependymoma Developed in the Extramedullary Location: A Case Report and Literature Review.

Intradural extramedullary (IDEM) ependymoma except for tumors originated from the filum terminale or conus medullaris is rare. The present study showed a case of IDEM ependymoma. A 16-year-old boy was referred to our hospital with a complaint of right hypochondriac pain and motor weakness in his right leg. MRI revealed a solitary intradural tumor at Th5-8 level with syringomyelia at Th2-4 level. Microscopic total tumor resection was performed with right hemi-laminectomy of Th4-9. Histological diagnosis was ependymoma (WHO grade 2). Although his leg weakness was worsened transiently, he showed improvement in leg weakness being able to go up and down the stairs 1 month after the surgery. There was no tumor recurrence until now, 7 years after the surgery, without any adjunctive therapies. A total of 44 cases of IDEM ependymoma had been reported in the past literatures. They are thought to arise from ependymal cells which remained during the process of neural tube closure. Like intramedullary ependymomas, most of the IDEM ependymomas have clear border to surrounding tissue and often removed completely. However, a small number of recurrences and malignant transformations had been reported after complete resections despite benign histological features tumors. In the case of totally resected low grade IDEM ependymoma, it is thought to be reasonable to perform long-term periodical radiographic follow-up without postoperative adjunctive therapy.

A Case of Atopic Myelitis with Cervical Cavernous Angioma.

Atopic myelitis, a type of myelitis which appears in patients with elevated serum levels of immunoglobulin E (IgE), occurs more commonly in the cervical spinal cord, but this mechanism has not yet been elucidated. Herein, we experienced a case of atopic myelitis developed during the growth of cervical cavernous angioma caused by bleeding. A 37-year-old woman suffered from hand swelling caused by a house cat licking. At the same time when cavernous angioma had grown, she experienced a numbness in her four extremities, and multifocal peritumoral hyperintense spinal cord signals were seen. The diagnosis of atopic myelitis was made because we observed significantly elevated levels of specific IgE antibody to cat dander. Symptoms disappeared immediately after steroid pulse therapy. We subsequently resected a cavernous angioma, and eosinophil invasion was found inside it. This is the first case report of atopic myelitis which developed in association with spinal cord vascular lesions. A local blood-brain barrier breakdown due to hemorrhagic lesions of the spinal cord may have contributed to the onset of atopic myelitis.

Surgical Treatment for Occipital Condyle Fracture, C1 Dislocation, and Cerebellar Contusion with Hemorrhage after Blunt Head Trauma.

Occipital condyle fractures (OCFs) have been treated as rare traumatic injuries, but the number of reported OCFs has gradually increased because of the popularization of computed tomography (CT) and magnetic resonance imaging (MRI). The patient in this report presented with OCFs and C1 dislocation, along with traumatic cerebellar hemorrhage, which led to craniovertebral junction instability. This case was also an extremely rare clinical condition in which the patient presented with traumatic lower cranial nerve palsy secondary to OCFs. When the patient was transferred to our hospital, the occipital bone remained defective extensively due to surgical treatment of cerebellar hemorrhage. For this reason, concurrent cranioplasty was performed with resin in order to fix the occipital bone plate strongly. The resin-made occipital bone was used to secure a titanium plate and screws enabled us to perform posterior fusion of the craniovertebral junction. Although the patient wore a halo vest for 3 months after surgery, lower cranial nerve symptoms, including not only neck pain but also paralysis of the throat and larynx, improved postoperatively. No complications were detected during outpatient follow-up, which continued for 5 years postoperatively.

[Juxta-facet Cyst Associated with Conjoined Nerve Roots:A Case Report].

We report a case of a patient with a juxta-facet cyst and conjoined nerve roots. A 66-year-old man presented with left leg pain from the past 4 months. Neurological examinations revealed L5 and S1 radiculopathy on the left side. Magnetic resonance imaging(MRI)detected a mass lesion located near the left intervertebral joint at the level of L5/S1 and canal stenosis at the level of L3/L4. A juxta-facet cyst was diagnosed by arthrography. We performed a curettage and resection of the mass, posterior lumbar interbody fusion at the level of L5/S1, and laminectomy at the level of L3/L4. Conjoined left L5/S1 nerve roots were observed during surgery. The patient recovered from the symptoms of L5 and S1 radiculopathy immediately after surgery. Postoperative review of the preoperative computed tomography images revealed bony abnormality in the L5/S1 joint. We speculate that the bony abnormality may be associated with the development of conjoined nerve roots and the juxta-facet cyst.

Simultaneous discovery of cranial and spinal intradural chordomas: case report.

The present case illustrates the unexpected occurrence of intradural chordomas that were simultaneously discovered in cranial and spinal locations. A 63-year-old female presented with weakness in the left upper extremity. The patient visited a local doctor and underwent brain computerized tomography (CT). CT revealed a brain tumor, and she was referred to our hospital. Brain magnetic resonance imaging (MRI) demonstrated a midline intradural retroclival tumor in addition to an intradural extramedullary mass lesion at the level of C1-C2. The patient developed a spastic gait disturbance that forced her to use a cane. She underwent laminectomy at C1-C2 along with total removal of the tumor and showed no remarkable symptoms after surgery. Histopathological examination confirmed the diagnosis of chordoma. One month after the cervical surgery, the intracranial tumor was subtotally removed in intracranial surgery via the right subtemporal approach. Histopathological data were identical to that of the cervical tumor. The patient consulted another hospital and underwent gamma-knife surgery. Her neurological examination is relatively unchanged 20 months after the cervical surgery. This case suggests that neuroradiological evaluation should also be performed for an intradural spinal chordoma when an intracranial chordoma is detected. Careful determination of the tumor responsible for the symptoms is necessary if an intradural spinal chordoma is simultaneously detected with an intracranial chordoma.

Incidental Detection of Primary Spinal Malignant Melanoma before Central Nervous System Dissemination.

The present case illustrates the incidental detection of a primary malignant melanoma of the thoracic spinal cord before central nervous system dissemination. A 54-year-old female fell down and bruised the thoracolumbar region. The patient visited a local doctor and underwent magnetic resonance imaging (MRI) of the thoracic and lumbar spine to rule out vertebral fractures. MRI revealed no vertebral fracture, but an intradural extramedullary mass was observed at the T12 level. She was referred to our hospital in October 2008. MRI showed that the mass appeared hyperintense on T1-weighted images and hypointense on T2-weighted images. T1-weighted MRI with gadolinium showed a mild homogeneous enhancement of the lesion. The patient underwent laminectomy at T11-L1, along with the complete removal of the tumor, and she exhibited no remarkable symptoms after surgery. Histopathological examination confirmed the diagnosis of malignant melanoma. Malignant melanoma was not detected elsewhere in the body. Neither radiotherapy nor chemotherapy was performed after surgery. Her neurological examination was unremarkable 5 years after the surgery and no tumor recurrence was detected. The present case suggests that patients with primary spinal malignant melanoma may survive >5 years without recurrence after complete surgical removal of the tumor alone. Complete removal of the tumor before central nervous system dissemination may be critical for treatment in such cases. Precise diagnosis via MRI may increase the detection of primary spinal malignant melanoma before central nervous system dissemination, thus facilitating prompt surgical removal, improving the prognosis of patients.

Radiation-induced spinal cord anaplastic astrocytoma subsequent to radiotherapy for testicular seminoma.

A 54-year-old man presented with a very rare case of radiation-induced intramedullary spinal cord anaplastic astrocytoma, which developed 37 years after radiotherapy for testicular seminoma. The patient presented with weakness and numbness of the left lower extremity that had gradually aggravated for 3 months. Magnetic resonance imaging demonstrated an intramedullary mass lesion with syringomyelia at the T9 to T12 levels. Subtotal removal of the tumor was performed using standard microsurgical technique. Histological examination revealed anaplastic astrocytoma. Although radiotherapy was seriously considered, chemotherapy was employed as adjuvant therapy considering the previous treatment. Although his neurological status improved transiently after surgery, relentless neurological decline occurred and resulted in death 9 months following surgery. Considering that subtotal removal of the tumor and chemotherapy had little influence on the quality of life and the length of survival in our case, cordectomy may be the optimum treatment for patients with radiation-induced spinal intramedullary malignant astrocytoma.

Neuropsychological improvement in patients with cervical spondylotic myelopathy after posterior decompression surgery.

Patients with cervical spondylotic myelopathy sometimes complain of cognitive dysfunction, which may be coincidence. However, cognitive dysfunction may be related to disorders of the cervical spine and/or spinal cord. This study investigated cognitive dysfunction in patients with cervical spinal disorders. A total of 79 patients with cervical spondylotic myelopathy (40 women and 39 men, mean age 61.2 years) underwent cervical laminoplasty between January 2006 and July 2007. Ten of these 79 patients (7 women and 3 men, mean age 65.2 years) complained of moderate to severe memory disturbances. These 10 patients underwent neuroimaging studies and a battery of neuropsychological tests consisting of the mini-mental state examination, Kohs Block Design Test, Miyake Memory Test, Benton Visual Retention Test (BVRT), and "kana-hiroi" test before and 3 months after surgery. Brain magnetic resonance imaging showed no organic brain lesions in the 10 patients, but single photon emission computed tomography demonstrated reduced regional cerebral blood flow in the posterior cortical areas in eight patients before surgery. Neuropsychological test scores showed statistically significant improvement after surgery in the Kohs Block Design Test and the BVRT, which measure visuospatial perception and reflect the function of the parietal and/or occipital lobes (p < 0.05). The practice effect may have contributed to the neuropsychological improvements, but this study suggests that cervical spinal disorders may affect cognitive functions and that surgical treatment can ameliorate such effects.

Technical improvements and results of open-door expansive laminoplasty with hydroxyapatite implants for cervical myelopathy.

OBJECTIVE: A new, modified technique of cervical open-door laminoplasty with hydroxyapatite implants was developed to enlarge the spinal canal in stable fashion yet preserve the architecture of the cervical spine and surrounding tissues. To assess the efficacy of this technique, a retrospective review of neurological and radiological outcomes after cervical laminoplasty was conducted. METHODS: Clinical charts and cervical x-rays of 151 patients with cervical stenotic myelopathy were reviewed. Patients were treated with the cervical laminoplasty between May 2001 and January 2002. The patient group comprised 69 women and 82 men ranging in age from 30 to 86 years (mean, 63 yr). Neurological outcomes were evaluated according to the Japanese Orthopaedic Association grade. To assess alignment and mobility of the cervical spine, the C2-C7 angle was used. RESULTS: The average Japanese Orthopaedic Association grade was 8.1 +/- 2.5 before surgery and 15.2 +/- 1.5 at 1 year after surgery (P < 0.01). No neurological complications were observed. The average C2-C7 angle at the neutral position increased from 8.3 +/- 11.7 degrees before surgery to 14.9 +/- 11.6 degrees at 1 year after surgery (P < 0.01). The range of motion between C2 and C7 was 36.9 +/- 12.5 degrees and 29.1 +/- 10.8 degrees before and 1 year after surgery, respectively. CONCLUSION: A new modified technique of cervical open-door laminoplasty described herein offers some solutions to the problems associated with conventional techniques of cervical laminoplasty.