Prevention of spinal cord injury using brain-evoked muscle-action potential (Br(E)-MsEP) monitoring in cervical spinal screw fixation.

PURPOSE: The goal of the study was to examine waveform deterioration in intraoperative monitoring during posterior fusion with a cervical screw. This surgery is useful for alignment correction, but worsening of neurological symptoms may occur in association with screw insertion and rod installation. Therefore, spinal cord monitoring is important for safe surgery. METHODS: The study included 25 cases treated with posterior fusion with a cervical screw. Waveform deterioration was defined as an intraoperative amplitude <50% of the control waveform. Comparisons were made between cases with normal and deteriorated waveforms. RESULTS: Intraoperative waveform deterioration occurred in nine cases, including after screw insertion in 8 and after rod installation in one. The nine patients with deteriorated waveforms had a significantly lower preoperative JOA score (8.8 vs. 11.2, P < 0.05) and a tendency for more frequent high signal intensity on MRI [67% (6/9) vs. 31% (5/16), P = 0.087]. Cases in which stenosis was greatest at the apex of the cervical lordosis had significantly more frequent intraoperative waveform deterioration [46% (6/13) vs. 0% (0/8), P < 0.05]. In cases in which the narrowest segment was at the apex of the cervical lordosis, screw insertion before compared to after decompression significantly increased waveform deterioration [67% (6/9) vs. 0% (0/4), P < 0.05]. CONCLUSION: Intraoperative waveform deterioration in posterior cervical screw fixation is associated with severe preoperative symptoms, location of the narrowest segment, and screw insertion before decompression. It is particularly desirable to perform decompression before screw insertion in cases with the narrowest segment at the apex of the cervical lordosis.

Analysis of cervical kyphosis and spinal balance in young idiopathic scoliosis patients classified by the apex of thoracic kyphosis.

PURPOSE: Sagittal balance has recently been the focus of studies aimed at understanding the correction force required for both coronal and sagittal malalignment. However, the correlation between cervical kyphosis and sagittal balance in AIS patients has yet to be thoroughly investigated. This study aimed to clarify the correlation between cervical alignment and spinal balance in patients with adolescent idiopathic scoliosis (AIS). Here, we hypothesized that cervical kyphosis patients can be classified into groups by the apex of thoracic kyphosis. METHODS: This study included 92 AIS patients (84 females, 8 males; mean age, 15.1 years). Patients were divided into the cervical lordosis (CL), cervical sigmoid (CS), or cervical kyphosis (CK) groups and further classified according to the apex of thoracic kyphosis into High (above T3), Middle (T4-T9), and Low (below T10) groups. RESULTS: There were 17 (18.5 %), 22 (23.9 %), and 53 (57.6 %) patients with CL, CS, and CK, respectively. In the CK group, 13 had CK-High, 35 had CK-Middle, and 5 had CK-Low. The C7 sagittal vertical axis (C7SVA) measurements were most backward in CK-High and most forward in CK-Low. The T5-12 kyphosis (TK) measurement was significantly lower in CK-High. CONCLUSIONS: Most AIS patients had kyphotic cervical alignment. Patients with CK can be classified as having CK-High, CK-Middle, or CK-Low according to the apex of thoracic kyphosis. CK-High is due to thoracic hypokyphosis with a backward balanced C7SVA. CK-Middle is well-balanced cervical kyphosis. CK-Low has forward-bent global kyphosis of the cervicothoracic spine that positioned the C7SVA forward.

Prevalence and distribution of ossification of the supra/interspinous ligaments in symptomatic patients with cervical ossification of the posterior longitudinal ligament of the spine: a CT-based multicenter cross-sectional study.

BACKGROUND: Supra/interspinous ligaments connect adjacent spinous processes and act as a stabilizer of the spine. As with other spinal ligaments, it can become ossified. However, few report have discussed ossification supra/interspinous ligaments (OSIL), so its epidemiology remains unknown. We therefore aimed to investigate the prevalence and distribution of OSIL in symptomatic patients with cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: The participants of our study were symptomatic patients with cervical OPLL who were diagnosed by standard radiographs of the cervical spine. The whole spine CT data as well as clinical parameters such as age and sex were obtained from 20 institutions belong to the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament (JOSL). The prevalence and distribution of OSIL and the association between OSIL and clinical parameters were reviewed. The sum of the levels involved by OPLL (OP-index) and OSIL (OSI-index) as well as the prevalence of ossification of the nuchal ligament (ONL) were also investigated. RESULTS: A total of 234 patients with a mean age of 65 years was recruited. The CT-based evidence of OSIL was noted in 68 (54 males and 14 females) patients (29%). The distribution of OSIL showed a significant thoracic preponderance. In OSIL-positive patients, single-level involvement was noted in 19 cases (28%), whereas 49 cases (72%) presented multi-level involvement. We found a significant positive correlation between the OP-index grade and OSI-index. ONL was noted at a significantly higher rate in OSIL-positive patients compared to negative patients. CONCLUSIONS: The prevalence of OSIL in symptomatic patients with cervical OPLL was 29%. The distribution of OSIL showed a significant thoracic preponderance.

Nogo receptor 1 is expressed in both primary cultured glial cells and neurons.

Nogo receptor (NgR) is common in myelin-derived molecules, i.e., Nogo, MAG, and OMgp, and plays important roles in both axon fasciculation and the inhibition of axonal regeneration. In contrast to NgR's roles in neurons, its roles in glial cells have been poorly explored. Here, we found a dynamic regulation of NgR1 expression during development and neuronal injury. NgR1 mRNA was consistently expressed in the brain from embryonic day 18 to postnatal day 25. In contrast, its expression significantly decreased in the spinal cord during development. Primary cultured neurons, microglia, and astrocytes expressed NgR1. Interestingly, a contusion injury in the spinal cord led to elevated NgR1 mRNA expression at the injury site, but not in the motor cortex, 14 days after injury. Consistent with this, astrocyte activation by TGFß1 increased NgR1 expression, while microglia activation rather decreased NgR1 expression. These results collectively suggest that NgR1 expression is enhanced in a milieu of neural injury. Our findings may provide insight into the roles of NgR1 in glial cells.

Spinal sagittal balance substantially influences locomotive syndrome and physical performance in community-living middle-aged and elderly women.

OBJECTIVES: Spinal sagittal imbalance has been well known risk factor of decreased quality of life in the field of adult spinal deformity. However, the impact of spinal sagittal balance on locomotive syndrome and physical performance in community-living elderly has not yet been clarified. The present study investigated the influence of spinal sagittal alignment on locomotive syndrome (LS) and physical performance in community-living middle-aged and elderly women. METHODS: A total of 125 women between the age of 40-88 years (mean 66.2 ± 9.7 years) who completed the questionnaires, spinal mouse test, physical examination and physical performance tests in Yakumo study were enrolled in this study. Participants answered the 25-Question Geriatric Locomotive Function Scale (GLFS-25), the visual analog scale (VAS) for low back pain (LBP), knee pain. LS was defined as having a score of >16 points on the GLFS-25. Using spinal mouse, spinal inclination angle (SIA), thoracic kyphosis angle (TKA), lumbar lordosis angle (LLA), sacral slope angle (SSA), thoracic spinal range of motion (TSROM), lumbar spinal range of motion (LSROM) were measured. Timed-up-and-go test (TUG), one-leg standing time with eyes open (OLS), and maximum stride, back muscle strength were also measured. The relationship between spinal sagittal parameters and GLFS-25, VAS and physical performance tests were analyzed. RESULTS: 26 people were diagnosed as LS and 99 were diagnosed as non-LS. LBP and knee pain were greater, physical performance tests were poorer, SIA were greater, LLA were smaller in LS group compared to non-LS group even after adjustment by age. SIA significantly correlated with GLFS-25, TUG, OLS and maximum stride even after adjustment by age. The cutoff value of SIA for locomotive syndrome was 6°. People with a SIA of 6° or greater were grouped as "Inclined" and people with a SIA of less than 6° were grouped as "Non-inclined". 21 people were "Inclined" and 104 were "Non-inclined". Odds ratio to fall in LS of Inclined group compared to Non-inclined group is 5.0. GLFS-25 were significantly higher, VAS for LBP were greater, TUG, OLS and maximum stride were poorer in Inclined group compared to Non-inclined group even after adjustment by age. CONCLUSIONS: The present study demonstrated that spinal sagittal balance influences the LS and physical performance in community-living middle-aged and elderly women. SIA is a useful spinal parameter to evaluate the risk of LS, and its cutoff value is 6°.

Predictive factors for a distal adjacent disorder with L3 as the lowest instrumented vertebra in Lenke 5C patients.

OBJECTIVE: To investigate what type of Lenke 5C patient benefits most from a fusion to L3 as the LIV. METHODS: The subjects were 16 patients who underwent fusion surgery to L3 as the lowest instrumented vertebra (LIV), and who were then observed for a minimum of 2 years postoperatively. We considered an unsatisfactory radiologic outcome for the distal adjacent curve (DAD) to be an L3 or L4 tilt angle less than 10° or L3/4 disc wedging less than 10°. Patients were divided into 2 groups based on the radiologic outcome of the distal curve: the distal adjacent disorder+ (DAD+) and the distal adjacent disorder-(DAD-). We compared global balance, Cobb angles (thoracic and lumbar), L3 and L4 tilt angles and L3/4/5 disc angles between the 2 groups on preoperative, postoperative and final radiographs. RESULTS: Seven patients (43.8 %) met the criteria for the DAD+ group. On preoperative radiographs, there was a significant difference in the L3/4 disc angle: the DAD+ group opened to the preoperative convex side (-2.1° ± 3.0°) and the DAD- group opened to the preoperative concave side (4.7° ± 5.1°). The standing L3- and L4-CSVL and the L4-CSVL under traction were significantly different. CONCLUSIONS: In Lenke 5C patients who underwent fusion surgery to L3 as the LIV, preoperative LIV (L3), LIV + 1 (L4) translation and L3/4 disc angle on standing, plus LIV + 1 translation under traction were very important parameters correlating with postoperative global coronal balance.

Tuberculous meningitis with dementia as the presenting symptom after intramedullary spinal cord tumor resection.

Early-stage TB meningitis has no specific symptoms in patients, potentially leading to delayed diagnosis and consequently worsening prognosis. The authors present the fatal case with a delayed diagnosis of tuberculous (TB) meningitis with dementia as the presenting symptom after intramedullary spinal cord tumor resection. The medical records, operative reports, and radiographical imaging studies of a single patient were retrospectively reviewed. A 77-year-old man who underwent thoracic intramedullary hemangioblastoma resection for 2 times. The postoperative course was uneventful, but 1.5 months after surgery, the patient suffered from dementia with memory loss and diminished motivation and speech in the absence of a fever. No abnormalities were detected on blood test, brain computed tomography and cerebrospinal fluid (CSF) analysis. A sputum sample was negative for Mycobacterium tuberculosis in the QuantiFERON®-TB Gold (QFT-G) In-Tube Test and the tuberculin skin test was also negative. The patient was diagnosed with senile dementia by a psychiatrist. However, the patient's symptoms progressively worsened. Despite the absence of TB meningitis findings, we suspected TB meningitis from the patient's history, and administered a four-drug regimen. However the patient died 29 days after admission, subsequently M. tuberculosis was detected in the CSF sample. This case is a rare case of TB meningitis initially mistaken for dementia after intramedullary spinal cord tumor resection. Symptoms of dementia after intramedullary spinal cord tumor resection should first be suspected as one of TB meningitis, even if the tests for meningitis are negative. We propose that anti-tuberculosis therapy should be immediately initiated in cases of suspected TB meningitis prior to positive identification on culture.

Fatal case of cervical blunt vascular injury with cervical vertebral fracture: a case report.

Blunt cerebrovascular injury (BCVI) is usually caused by neck trauma that predominantly occurs in high-impact injuries. BCVI may occur due to damage to both the vertebral and carotid arteries, and may be fatal in the absence of appropriate treatment and early diagnosis. Here, we describe a case of cerebral infarction caused by a combination of a lower cervical spinal fracture and traumatic injury to the carotid artery by a direct blunt external force in a 52-year-old man. Initially, there was no effect on consciousness, but 6 hours later loss of consciousness occurred due to traumatic dissection of the carotid artery that resulted in a cerebral infarction. Brain edema was so extensive that decompression by emergency craniectomy and internal decompression were performed by a neurosurgeon, but with no effect, and the patient died on day 7. This is a rare case of cerebral infarction caused by a combination of a lower cervical spinal fracture and traumatic injury to the carotid artery. The case suggests that cervical vascular injury should be considered in a patient with a blunt neck trauma and that additional imaging should be performed.

Utility of a 3-dimensional full-scale NaCl model for rib strut grafting for anterior fusion for cervicothoracic kyphosis.

In severe spinal deformity, pain and neurological disorder may be caused by spinal cord compression. Surgery for spinal reconstruction is desirable, but may be difficult in a case with severe deformity. Here, we show the utility of a 3D NaCl (salt) model in preoperative planning of anterior reconstruction using a rib strut in a 49-year-old male patient with cervicothoracic degenerative spondylosis. We performed surgery in two stages: a posterior approach with decompression and posterior instrumentation with a pedicle screw; followed by a second operation using an anterior approach, for which we created a 3D NaCl model including the cervicothoracic lesion, spinal deformity, and ribs for anterior reconstruction. The 3D NaCl model was easily scraped compared with a conventional plaster model and was useful for planning of resection and identification of a suitable rib for grafting in a preoperative simulation. Surgery was performed successfully with reference to the 3D NaCl model. We conclude that preoperative simulation with a 3D NaCl model contributes to performance of anterior reconstruction using a rib strut in a case of cervicothoracic deformity.

Surgically treated cases of lumbar spondylolysis and isthmic spondylolisthesis: a multicenter study.

STUDY DESIGN: Prospective database study. OBJECTIVES: To grasp the characteristics of surgically treated cases with lumbar spondylolysis or isthmic spondylolisthesis. SUMMARY OF BACKGROUND DATA: A detailed analysis of surgically treated cases with spondylolysis or isthmic spondylolisthesis has never been reported. An epidemiological study in Japan conducted on 2000 subjects found the incidence of lumbar spondylolysis in the Japanese general population (population-based study) to be 5.9% (males: 7.9%, females: 3.9%). Among 124 vertebrae with spondylolysis, there were 0.8% L2 lesions, 3.2% L3 lesions, 5.6% L4 lesions, and 90.3% L5 lesions, including 5 cases (4.3%) with multiple-level lesions. METHODS: We have been registering surgically treated spine cases in our database since 2000. From this database, we prospectively collected cases with lumbar spondylolysis or isthmic spondylolisthesis that were treated surgically between January 2000 and December 2009. We determined the age at surgery, sex, and vertebral level of spondylolysis. RESULTS: Of the 564 spondylolysis patients treated surgically, 66.8% were male and 33.2% were female. The mean age at surgery was 52.5 years (range, 13-84 y). There were 585 vertebrae with spondylolysis including 21 cases (3.7%) with multiple-level lesions. L5 spondylolysis affected 432 vertebrae and was the most common location (73.8%), followed by 125 L4 lesions (21.4%), 24 L3 lesions (4.1%), and 2 L2 lesions (0.7%). CONCLUSIONS: The percentage of L4 lesions in our study was significantly higher and of L5 lesions was significantly lower than those lesions' percentages in the population-based study. L4 spondylolysis may be more unstable or cause clinical symptoms more frequently leading to more surgical intervention. The percentage of multiple-level spondylolysis was similar between the 2 studies, suggesting these patients respond relatively well to conservative treatment. The male/female ratio was 2:1 in both studies, indicating that males and females require surgery at a similar frequency.

Hyperamylasemia and pancreatitis following posterior spinal surgery.

BACKGROUND: Postoperative pancreatitis has primarily been reported as a complication of abdominal surgery, but there are some case reports of postoperative pancreatitis after spinal surgery. The objective of this study was to investigate a case series of hyperamylasemia and pancreatitis following posterior spinal surgery. METHODS: The serum amylase level was measured following posterior spinal surgery in the prone position. Patients were divided into groups with a normal serum amylase level (0-125 IU/L) and with hyperamylasemia (>125 IU/L), based on the upper limit of normal of 125 IU/L in our institution. Relationships among preoperative factors, perioperative factors, and the serum amylase level were investigated. RESULTS: Hyperamylasemia (serum amylase >125 IU/L) following posterior spinal surgery was found in 92 cases (35 %). Among perioperative factors, intraoperative estimated blood loss (EBL) and operating time were significantly higher in patients with high serum amylase than in patients with normal serum amylase (P < 0.01). In a multivariate regression model, intraoperative EBL (OR 1.001, 95 % CI 1.000-1.002; P = 0.001) and operation time (OR 1.006, 95 % CI 1.003-1.009; P = 0.006) were significantly associated with postoperative pancreatitis. Serum amylase levels of ≥ 5 times the upper limit of normal were found in six cases. Five of these cases were asymptomatic and one was caused by severe pancreatitis. CONCLUSIONS: In our case series, intraoperative blood loss caused a rise in the serum amylase level following posterior spinal surgery. Thus, this level should be carefully monitored after spinal surgery with significant blood loss. Clinical symptoms of pancreatitis, such as abdominal pain and vomiting, should also be monitored following spinal surgery.

Appropriate timing of surgical intervention for the proximal type of cervical spondylotic amyotrophy.

PURPOSE: The purposes of this study were to evaluate the clinical outcome after surgical treatment of patients with the proximal type of cervical spondylotic amyotrophy (CSA) and to explore the appropriate timing for surgical intervention. MATERIALS AND METHODS: A retrospective review was performed on a consecutive cohort of 41 patients who underwent surgical treatment for the proximal type of CSA between 1995 and 2011 at the Nagoya Spine Group Hospitals. We collected information regarding age, type of muscle atrophy, preoperative and final manual muscle test, duration of symptoms, high-intensity areas on T2-weighted MRI images, low-intensity areas on T1-weighted MRI images, levels of spinal canal stenosis, the compression lesion site, cervical kyphosis and surgical procedures (laminoplasty, anterior spinal fusion and posterior spinal fusion). Univariate analyses and multivariate logistic regression analysis were performed to identify correlates of a poor outcome. To explore the appropriate timing for performing surgery, we analyzed the data using receiver operating characteristic (ROC) analysis. RESULTS: The duration of CSA symptoms was 11.6 months on average. The surgical results were excellent for 25 patients, good for six, fair for nine and poor for one. On multivariate logistic regression analysis, the duration of symptoms was statistically associated with a poor surgical outcome (OR 1.393, p = 0.011). ROC analysis demonstrated that 4.3 months from the onset of CSA symptoms was the appropriate time to undergo surgery. CONCLUSIONS: Our results indicate that we should recommend surgical intervention to patients with the proximal type of CSA within about 4 months after the onset of symptoms if conservative treatment has not been successful.

Volumetric change in interbody bone graft after posterior lumbar interbody fusion (PLIF): a prospective study.

PURPOSE: The purpose of this study is to quantify the change in the volume of the interbody bone graft after the PLIF and monitor the change over time for subsequent analysis. METHODS: The 114 cases were selected as the subjects of this study. The observation period was for 5 years following the surgery. The volume of the bone graft in the interbody space was calculated by summing up the cross-sectional area of the bone graft on each axial image multiplied by the height (2 mm) (the volume of the two cages was excluded). The volume ratio (%) = (bone graft volume)/(total volume of the interbody space - cage volume) was used for the purpose of evaluation. RESULTS: The volumetric change of the bone graft was 51 % (3 months), 53 % (6 months), 54 % (1 year), 55 % (2 years), 59 % (3 years), 62 % (4 years), and 72 % (5 years), indicating a continued increase up to the 5-year mark. In particular, a significant increase was observed from the second year as compared with the previous years' result. Additionally, the volumetric increase from the second year to the fifth year was significantly higher than that before the second year. CONCLUSIONS: The post-PLIF volumes of interbody bone grafts exhibited increases particularly from the second to fifth years after the procedure. Even the elderly and those with poor bone qualities can expect to have volumetric increases over time. Sufficient interbody space should be secured for accommodating bone grafts by intraoperative reduction, wherever possible.

Chronic spontaneous lumbar epidural hematoma simulating extradural spinal tumor: a case report.

Spinal epidural hematoma (SEH) is an uncommon disorder, and chronic SEHs are rarer than acute SEHs. However, there is few reported involving the bone change of the vertebral body in chronic SEHs. We present a case report of lumbar epidural hematoma that required differentiation from extramedullary spinal tumors by a long process because the CT scan revealed scalloping of the vertebral body and review the relevant literature. A 78-year-old man had experienced a gradual onset of low back pain and excruciating pain in both legs. Lumbar MRI on T1-weighted images revealed a space-occupying lesion with a hyperintense signal relative to the spinal cord with no enhancement on gadolinium adminisration. Meanwhile, T2-weighted images revealed a heterogeneous intensity change, accompanying a central area of hyperintense signals with a hypointense peripheral border at the L4 vertebra. Moreover, the CT scan demonstrated scalloping of the posterior wall of the L4 vertebral body which is generally suspected as the CT finding of spainal tumor. During the epidural space exploration, we found a dark red-colored mass surrounded by a capsular layer, which was fibrous and adhered to the flavum and dura mater. Microscopic histological examination of the resected mass revealed a mixture of the relatively new hematoma and the hematoma that was moving into the connective tissue. Accordingly, the hematoma was diagnosed as chronic SEH. The particular MRI findings of chronic SEHs are helpful for making accurate preoperative diagnoses of this pathology.

Recurrence of solitary fibrous tumor of the cervical spinal cord.

Solitary fibrous tumor (SFT) mostly originates from the pleura because of proliferation of fibroblast cells. It is extremely rare for the tumor to originate from the spinal cord. Here, we report a rare case of SFT in the spinal cord that recurred repeatedly and progressed from intramedullary to extramedullary. A 40-year-old man underwent C4-5 intramedullary and extramedullary tumor resection in another hospital. Eighteen years later, he experienced symptoms of myelopathy because of tumor recurrence; therefore, he consulted with our hospital and underwent tumor resection again. During surgery, we found that the tumor had an intramedullary and extramedullary location. Only partial resection was possible because of intraoperative deterioration in the compound motor action potential (CMAP). After resection, the pathological diagnosis was SFT. The postoperative course was good. However, two years later, a third tumor resection was required because of dysuria and tumor growth. In this surgery, total resection of the tumor was possible without intraoperative deterioration of the CMAP. The tumor has not subsequently recurred. However, SFT recurrence is relatively common and careful follow-up is required for early detection of recurrence, even after successful removal of the tumor.

Primary cauda equina lymphoma: case report and literature review.

The central nervous system, in particular the spinal cord, is a rare site for primary lymphoma occurrence, with very few published cases. We report an extremely rare primary lymphoma in the cauda equina in a single case with literature review. An immunocompetent 59-year-old male, who complained of progressive low back and bilateral leg pain for 7 months, was studied. Magnetic resonance imaging (MRI) revealed an intradural space-occupying lesion from T12 to S1, poorly demarcated to the normal cauda equina. The intradural lesion showed T1 low intensity, T2 low isointensity, and marked homogeneous enhancement with gadolinium-diethylenetriaminepentaacetic acid on MRI. We performed spinal tap to obtain additional information about the intradural lesion. Large-sized atypical lymphoid cells were found during pathological examination. Fluorodeoxyglucose accumulation was found only in the lumbar area, which corresponded with the MRI findings, and the primary lymphoma site was defined as the cauda equina area. For further detailed pathological diagnosis, we performed surgical biopsy of the cauda equina. Morphological and immunohistochemical assessment made a diagnosis of diffuse large B-cell lymphoma of the cauda equina. The patient received radiotherapy to the lumbosacral area (50 Gy) and methotrexate (MTX) therapy after surgery. The patient was able to walk without help after the therapies. Follow-up MRI performed 1 year after biopsy showed remission of the lesion. MRI and spinal tap were effective tools for the early definitive diagnosis of cauda equina lymphoma. Combined treatment with radiotherapy and MTX should be performed as early as possible.

Pedicle screws can be 4 times stronger than lateral mass screws for insertion in the midcervical spine: a biomechanical study on strength of fixation.

STUDY DESIGN: A biomechanical study. OBJECTIVE: To compare, in cervical vertebrae (C3-C6), the pullout strengths of pedicle screws and lateral mass screws after both types of screw had been subjected to a period of cyclic loading in 2 planes. SUMMARY OF BACKGROUND DATA: In posterior subaxial cervical fixation systems, screws are usually inserted into the lateral mass. As an alternative to lateral mass fixation, pedicle screw fixation became popular in the 1990s and was first used for lower cervical spine trauma cases. However, it is controversial as to whether lateral mass screw fixation in the upper-middle cervical spine offers as much biomechanical security as compared with pedicle screw fixation. METHODS: For each of the 32 vertebrae, 1 side was randomly chosen to receive a pedicle screw and the other side a lateral mass screw. The pedicle or lateral mass screws inserted into the first 16 vertebrae were cyclically loaded to simulate torsion and the remaining 16 vertebrae were cyclically loaded to simulate flexion/extension of the spine. At the end of the cyclic loading each screw was pulled out along its long axis. RESULTS: For the torsion group, the mean pullout strength of the pedicle screws was nearly 4 times greater than the mean pullout strength of the lateral mass screws (cf 762 N with 191 N). In contrast, the mean pullout strength of the pedicle screws in the flexion/extension group was only twice the mean pullout strength of the lateral mass screws (cf 571 N with 289 N). CONCLUSIONS: Not forgetting the potential risks of inserting pedicle screws in cervical vertebrae, pedicle screws are a better biomechanical choice than lateral mass screws for cervical fixation at the levels C3 through to C6.

Differentiation of spinal schwannomas and myxopapillary ependymomas: MR imaging and pathologic features.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: The objective of this study is to evaluate magnetic resonance imaging and pathologic features of spinal schwannomas (SCHs) and myxopapillary ependymomas (MPEs) with focus on differentiating 2 disease entities. SUMMARY OF BACKGROUND DATA: Few studies have reported on the differentiation of SCHs and MPEs. METHODS: Fifty-three patients were retrospectively reviewed with histologically confirmed spinal SCHs (41 patients) or MPEs (12 patients) of the cauda equina and/or conus medullaris. We evaluated neurological deterioration after surgery in association with the intraoperative findings of the tumor, as well as with the preoperative magnetic resonance images and postoperative histologic findings. RESULTS: Patients in the SCH group had a greater mean age at surgery and a greater mean disease duration. In the SCH group, all 24 tumors that were homogeneously hyperintense on the T2-weighted (T2W) images showed rim enhancement on the postcontrast T1-weighted (T1W) images. Moreover, all 14 of the SCHs with homogeneous enhancement on the postcontrast T1W images were isointense on the T2W images. However, in the MPE group, all 8 of the tumors that were homogeneously hyperintense on T2W images showed homogeneous enhancement on their postcontrast T1W images. CONCLUSIONS: It is very important to differentiate SCHs and MPEs before surgery, because there are reported cases of dissemination of MPEs through cerebrospinal fluid throughout the neuraxis; the tumor must be removed en block to prevent this. Although MPEs and SCHs may have similar imaging characteristics, detailed examination of the magnetic resonance T2W image and postcontrast T1W image facilitates their differentiation.

Radiologic evaluation after posterior instrumented surgery for thoracic ossification of the posterior longitudinal ligament: union between rostral and caudal ossifications.

STUDY DESIGN: Retrospective clinical study. OBJECTIVE: To investigate, using multislice CT images, how thoracic ossification of the posterior longitudinal ligament (OPLL) changes with time after thoracic posterior fusion surgery. SUMMARY OF BACKGROUND DATA: Few studies have evaluated thoracic OPLL preoperatively and post using computed tomography (CT). METHODS: The subjects included 19 patients (7 men and 12 women) with an average age at surgery of 52 years (38-66 y) who underwent indirect posterior decompression with corrective fusion and instrumentation at our institute. Minimum follow-up period was 1 year, and averaged 3 years 10 months (12-120 mo). Using CT images, we investigated fusion range, preoperative and postoperative Cobb angles of thoracic fusion levels, intraoperative and postoperative blood loss, operative time, hyperintense areas on preoperative MRI of thoracic spine and thickness of the OPLL on the reconstructed sagittal, multislice CT images taken before the operation and at 3 months, 6 months and 1 year after surgery. The basic fusion area was 3 vertebrae above and below the OPLL lesion. RESULTS: The mean operative time was 7 hours and 48 min (4 h 39 min-10 h 28 min), and blood loss was 1631 mL (160-11,731 mL). Intramedullary signal intensity change on magnetic resonance images was observed at the most severe ossification area in 18 patients. Interestingly, the rostral and caudal ossification regions of the OPLLs, as seen on sagittal CT images, were discontinuous across the disk space in all patients. Postoperatively, the discontinuous segments connected in all patients without progression of OPLL thickness by 5.1 months on average. CONCLUSIONS: All patients needing surgery had discontinuity across the disk space between the rostral and caudal ossified lesions as seen on CT. This discontinuity was considered to be the main reason for the myelopathy because a high-intensity area on magnetic resonance imaging was seen in 18 of 19 patients at the same level. Rigid fixation with instrumentation may allow the discontinuous segments to connect in patients without a concomitant thickening of the OPLL.

Impact of low back pain, knee pain, and timed up-and-go test on quality of life in community-living people.

BACKGROUND: The Japanese Orthopaedic Association (JOA) has proposed the term "locomotive syndrome" (LS) to designate a condition in people from high-risk groups with musculoskeletal disease who are highly likely to require nursing care at some point. This syndrome is caused by weakening of the musculoskeletal organs such as bone, joint, and muscle. The current study investigated factors that influence quality of life (QOL) loss caused by LS, which builds upon our previous study showing that LS affects individuals' QOL. METHODS: We enrolled 386 subjects >50 years old. Sex, age, body mass index and bone mineral density, plus physical function tests of grip strength, back muscle strength, maximum stride, 10-m gait time, functional reach (cm), timed up-and-go test (TUG) (s) and one-leg standing time (s), and the visual analogue scale assessments for leg numbness and knee, low back and leg pain were selected as independent variables in a multiple regression model for the JOA Back Pain Evaluation Questionnaire (JOABPEQ), the Short Form-36 (SF-36), and the Roland Morris Disability Questionnaire (RDQ) scores. RESULTS: Low back pain contributed significantly to all JOABPEQ scores. Knee pain and TUG contributed significantly to 4/5 and 3/5 of the JOABPEQ scores, respectively. Age, TUG, knee pain, and low back pain contributed significantly to the RDQ and the physical component summary of the SF-36. CONCLUSIONS: Low back and knee pain proved to be significant contributors to individuals' QOL. TUG might be the most valuable function test for effectively evaluating an individual's QOL.