Mitsuhiro Kamiya

C5 palsy after cervical laminoplasty: A MULTICENTRE STUDY

We have reviewed 1858 patients who had undergone a cervical laminoplasty and identified 43 (2.3%) who had developed a C5 palsy with a MMT (MRC) grade of 0 to 2 in the deltoid, with or without involvement of the biceps, but with no loss of muscular strength in any other muscles. The clinical features and radiological findings of patients with (group P; 43 patients) and without (group C; 100 patients) C5 palsy were compared. CT scanning of group P revealed a significant narrowing of the intervertebral foramen of C5 (p < 0.005) and a larger superior articular process (p < 0.05). On MRI, the posterior shift of the spinal cord at C4-5 was significantly greater in group P, than in group C (p < 0.01). This study is the first to correlate impairment of the C5 nerve root with a C5 palsy. It may be that early foraminotomy in susceptible individuals and the avoidance of tethering of the cord by excessive laminoplasty may prevent a post-operative palsy of the C5 nerve root.

Nitric oxide via macrophage iNOS induces apoptosis following traumatic spinal cord injury

To investigate the pathophysiological mechanisms involved in post-traumatic impairment of the spinal cord, we analyzed expression patterns of the inducible nitric oxide synthase (iNOS) gene following acute injury of rat spinal cord using a weight drop technique. PCR analysis revealed that iNOS mRNA appeared at 3-12 h after injury and declined thereafter. Immunohistochemical analysis showed that iNOS-positive cells invaded the lesioned area through the perivascular space at 6 h after injury. The population of these cells peaked at 24 h and then declined to disappear 3 days after injury. The iNOS-positive cells were also stained with ED-2 but not with ED-1 or OX-42, indicating that these cells were macrophages and/or perivascular cells. In parallel with the appearance of iNOS-positive cells, other cells emerged that were positively stained by the terminal deoxynucleotidyl-transferase-mediated dUDP-biotin nick end-labeling (TUNEL) assay. TUNEL-positive cells were scattered in the lesioned area 1 day after injury, but some in the surrounding area close to iNOS-positive cells. Administration of L-Ng-nitro-arginine methylester, a competitive inhibitor of NOS, resulted in a reduction of TUNEL-positive cells in the lesioned area. These results suggest that nitric oxide generated by iNOS of macrophages and/or perivascular cells plays a significant role in eliminating damaged cells from the lesioned area by apoptosis.

Up-regulation of glial cell line-derived neurotrophic factor (GDNF) following traumatic spinal cord injury.

We investigated the temporal and spatial expression patterns of the GDNF gene after subjecting rats to an acute contusion injury of the spinal cord using the weight drop technique. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that GDNF transcription in the spinal cord began to increase within 30 min after injury and peaked within 3 h. Immunohistochemical analysis showed GDNF immunoreactivity to be present mainly in microglia and macrophages 1 day after injury, but not in neurons or astrocytes. This immediate upregulation of GDNF gene expression may be a component of an inflammatory process and probably exerts a protective effect on neurons following spinal cord injury (SCI).

Association between a polymorphism of the transforming growth factor-β1 gene and genetic susceptibility to ossification of the posterior longitudinal ligament in Japanese patients

Study Design. A study was conducted to determine the association between polymorphism of the transforming growth factor-&bgr;1 (TGF-&bgr;1) gene and ossification of the posterior longitudinal ligament (OPLL) prevalence. Objective. To examine whether the T869→C polymorphism of the TGF-&bgr;1 gene is associated with genetic susceptibility to OPLL in Japanese subjects. Summary of Background Data. In the posterior longitudinal ligament, OPLL is associated with abnormal calcium metabolism. Several candidate genes are associated with the prevalence of OPLL. In the ossified matrix and chondrocytes of adjacent cartilaginous areas of OPLL, TGF-&bgr;1 is overexpressed. Methods. The TGF-&bgr;1 genotype was identified with an allele-specific polymerase chain reaction method in 319 Japanese subjects (46 subjects with OPLL and 273 control subjects). Results. There was a significant association between the T869→C genotype and the prevalence of OPLL in the cervical spine. Multivariable logistic regression analysis, adjusted for gender, age, height, and body weight, showed that the frequency of the C allele was significantly higher in subjects with OPLL than in control subjects. Conclusions. The T869→C polymorphism of the TGF-&bgr;1 gene is a genetic determinant of a predisposition to OPLL, with the C allele representing a risk factor for genetic susceptibility to OPLL in Japanese subjects. Therefore, TGF-&bgr;1 genotyping may be useful in the prevention of OPLL.

Selection of the Optimal Distal Fusion Level in Posterior Instrumentation and Fusion for Thoracic Hyperkyphosis: The Sagittal Stable Vertebra Concept

Study Design. Retrospective study. Objective. To determine the appropriate distal fusion level in posterior instrumentation and fusion for thoracic hyperkyphosis by investigating the relationship between the sagittal stable vertebra ([SSV]-the most proximal lumbar vertebral body touched by the vertical line from the posterior-superior corner of the sacrum), first lordotic vertebra (just caudal to the first lordotic disc), and selected lowest instrumented vertebra (LIV). Summary of Background Data. It has been recommended that the distal end vertebra and the first lordotic disc beyond the transitional zone distally be included in distal fusion for thoracic hyperkyphosis; however, we have seen distal junctional breakdown even when these rules have been followed. Methods. Thirty-one patients (mean age: 18 years, range: 13-38) who underwent long posterior instrumentation and fusion for thoracic hyperkyphosis with a minimum 2-year follow-up were reviewed. Preoperative diagnoses included Scheuermann kyphosis (n = 29), post-traumatic kyphosis (n = 1), and postlaminectomy kyphosis (n = 1). According to the distal fusion level, patients were divided into 2 groups. Group I (n = 24): LIV included the SSV; group II (n = 7): the LIV was proximal to the SSV. Patients were evaluated using standing radiographs and chart review. Results. Preoperative mean thoracic kyphosis was 86.6 ± 8.5° and 53.0 ± 10.4° at final follow-up with a correction rate of 39%. Preoperative average sagittal balance was slightly negative (−0.24 ± 3.8 cm), and became slightly more negative (−1.33 ± 2.8 cm) by final follow-up. There were no statistical differences in thoracic kyphosis between the 2 groups. However, there was a statistically significant difference with group II having a more posterior translation of the center of the LIV from the posterior sacral vertical line before surgery and at final follow-up (P = 0.003). In group I, distal junctional problems developed in 2 of 24 (8%) patients and in group II, problems occurred in 5 of 7 (71%) patients (P < 0.05). Despite extending the fusion to the first lordotic vertebra, distal junctional problems developed in 3 of 8 (38%) patients. Conclusion. The distal end of a fusion for thoracic hyperkyphosis should include the SSV. Levels that include the first lordotic vertebra but not the SSV are not always appropriate to prevent postoperative distal junctional kyphosis.

Multivariate analysis of C-5 palsy incidence after cervical posterior fusion with instrumentation

OBJECT Postoperative C-5 palsy is a significant complication resulting from cervical decompression procedures. Moreover, when cervical degenerative diseases are treated with a combination of decompression and posterior instrumented fusion, patients are at increased risk for C-5 palsy. However, the clinical and radiological features of this condition remain unclear. Therefore, the purpose of this study was to clarify the risk factors for developing postoperative C-5 palsy. METHODS Eighty-four patients (mean age 60.1 years) who had undergone posterior instrumented fusion using cervical pedicle screws to treat nontraumatic lesions were independently reviewed. The authors analyzed the medical records of some of these patients who developed postoperative C-5 palsy, paying particular attention to their plain radiographs, MRI studies, and CT scans. Risk factors for postoperative C-5 palsy were assessed using multivariate logistic regression analysis. The cutoff values for the pre- and postoperative width of the intervertebral foramen (C4-5) were determined by receiver operating characteristic curve analysis. RESULTS Ten (11.9%) of 84 patients developed postoperative C-5 palsy. Seven patients recovered fully from the neurological complications. The pre- and postoperative C4-5 angles showed significant kyphosis in the C-5 palsy group. The pre- and postoperative diameters of the C4-5 foramen on the palsy side were significantly smaller than those on the opposite side in the C-5 palsy group and those bilaterally in the non-C5 palsy group. Risk factors identified by multivariate logistic regression analysis were as follows: 1) ossification of the posterior longitudinal ligament (relative risk [RR] 7.22 [95% CI 1.03-50.55]); 2) posterior shift of the spinal cord (C4-5) (RR 1.73 [95% CI 1.00-2.98]); and 3) postoperative width of the C-5 intervertebral foramen (RR 0.33 [95% CI 0.14-0.79]). The cutoff values of the pre- and postoperative widths of the C-5 intervertebral foramen for C-5 palsy were 2.2 and 2.3 mm, respectively. CONCLUSIONS Patients with preoperative foraminal stenosis, posterior shift of the spinal cord, and additional iatrogenic foraminal stenosis due to cervical alignment correction were more likely to develop postoperative C-5 palsy after posterior instrumentation with fusion. Prophylactic foraminotomy at C4-5 might be useful when preoperative foraminal stenosis is present on CT. Furthermore, it might be useful for treating postoperative C-5 palsy. To prevent excessive posterior shift of the spinal cord, the authors recommend that appropriate kyphosis reduction should be considered carefully.

Surgical results of intramedullary spinal cord tumor with spinal cord monitoring to guide extent of resection.

OBJECT The authors investigated the outcome of intramedullary spinal cord tumor surgery, focusing on the effect of preoperative neurological status on postoperative mobility and the extent of tumor excision guided by intraoperative spinal cord monitoring prospectively. METHODS Intramedullary spinal cord tumor surgery was performed in 131 patients between 1997 and 2007. The authors compared the pre- and postoperative neurological status and examined the type of surgery in 106 of these patients. A modified McCormick Scale (Grades I-V) was used to assess ambulatory ability (I = normal ambulation; II = mild motor sensory deficit, independent without external aid; III = independent with external aid; IV = care required; and V = wheelchair required). The type of surgery was classified into 4 levels: total resection, subtotal resection, partial resection, and biopsy. RESULTS The 106 patients consisted of 47 females and 59 males, whose average age was 42.5 years (range 6-75 years). The mean follow-up period was 7.3 years (range 2.5 months-21 years). The tumor types included astrocytoma (12 cases), ependymoma (46 cases), hemangioblastoma (16 cases), cavernous hemangioma (17 cases), and others (15 cases overall: gangliocytoma, 1; germ cell tumor, 1; lymphoma, 3; neurinoma, 1; meningioma, 1; oligodendroglioma, 1; sarcoidosis, 2; glioma, 1; and unknown, 4). Initial total excision, subtotal resection, partial resection, biopsy, and duraplasty were performed in 59, 12, 22, 12, and 1 patients, respectively. According to the preoperative McCormick Scale, ambulatory status was classified as Grades I, II, III, IV, and V in 41(38%), 30 (28%), 14 (13%), 19 (19%), and 2 (2%) patients, respectively. Thirty-three (31%) of 106 patients suffered postoperative neurological deterioration. The number of patients who did not lose ambulatory ability or who achieved an ambulatory status of Grade I or II postoperatively was 33 (80%), 21 (70%), 10 (71%), 8 (42%), and 1 (50%) in patients with preoperative Grades I, II, III, IV, and V, respectively. Total excision was performed in 31 (79%) of 39 patients with preoperative Grade I, 12 (40%) of 30 patients with Grade II, 7 (50%) of 14 patients with Grade III, and 9 of 21 patients (38%) with Grade IV or V, indicating that the rate of total excision was significantly higher in patients with Grade I status. CONCLUSIONS The postoperative ambulatory ability was excellent in patients with a good preoperative neurological status. Total excision in patients with Grade I or II ambulation was associated with a good prognosis for postoperative mobility. However, the rate of postoperative deterioration was 31.5%, which is relatively high, and patients should be fully informed of this concern prior to intramedullary spinal cord tumor surgery.

Complications of cervical pedicle screw fixation for nontraumatic lesions: a multicenter study of 84 patients

OBJECT The cervical pedicle screw (PS) provides strong stabilization but poses a potential risk to the neurovascular system, which may be catastrophic. In particular, vertebrae with degenerative changes complicate the process of screw insertion, and PS misplacement and subsequent complications are more frequent. The purpose of this study was to evaluate the peri- and postoperative complications of PS fixation for nontraumatic lesions and to determine the risk factors of each complication. METHODS Eighty-four patients who underwent cervical PS fixation for nontraumatic lesions were independently reviewed to identify associated complications. The mean age of the patients was 60.1 years, and the mean follow-up period was 4.1 years (range 6-168 months). Pedicle screw malpositioning was classified on postoperative CT scans as Grade I (< 50% of the screw outside the pedicle) or Grade II (≥ 50% of the screw outside the pedicle). Risk factors of each complication were evaluated using a multivariate analysis. RESULTS Three hundred ninety cervical PSs and 24 lateral mass screws were inserted. The incidence of PS misplacement was 19.5% (76 screws); in terms of malpositioning, 60 screws (15.4%) were classified as Grade I and 16 (4.1%) as Grade II. In total, 33 complications were observed. These included postoperative neurological complications in 11 patients in whom there was no evidence of screw misplacement (C-5 palsy in 10 and C-7 palsy in 1), implant failure in 11 patients (screw loosening in 5, broken screws in 4, and loss of reduction in 2), complications directly attributable to screw insertion in 5 patients (nerve root injury by PS in 3 and vertebral artery injury in 2), and other complications in 6 patients (pseudarthrosis in 2, infection in 1, transient dyspnea in 1, transient dysphagia in 1, and adjacent-segment degeneration in 1). The multivariate analysis showed that a primary diagnosis of cerebral palsy was a risk factor for postoperative implant failure (HR 10.91, p = 0.03) and that the presence of preoperative cervical spinal instability was a risk factor for both Grade I and Grade II screw misplacement (RR 2.12, p = 0.03), while there were no statistically significant risk factors for postoperative neurological complications in the absence of evidence of screw misplacement or complications directly attributable to screw insertion. CONCLUSIONS In the present study, misplacement of cervical PSs and associated complications occurred more often than in previous studies. The rates of screw-related neurovascular complications and neurological deterioration unrelated to PSs were high. Insertion of a PS for nontraumatic lesions is surgically more challenging than that for trauma; consequently, experienced surgeons should use PS fixation for nontraumatic cervical lesions only after thorough preoperative evaluation of each patients cervical anatomy and after considering the risk factors specified in the present study.

Vertebral reconstruction with biodegradable calcium phosphate cement in the treatment of osteoporotic vertebral compression fracture using instrumentation.

Objective: To assess the efficacy of posterior instrumentation and vertebral reconstruction with biodegradable calcium phosphate cement (CPC) in the treatment of osteoporotic vertebral compression fracture with neurologic deficit. Background: Vertebroplasty consists of the injection of polymethylmethacrylate (PMMA) cement into the vertebral body. While PMMA has high mechanical strength, it cures fast and thus allows only a short handling time. Other potential problems of using PMMA injection may include damage to surrounding tissues due to the high polymerization temperature or by the toxic unreacted monomer and the lack of long-term biocompatibility. Bone mineral cements such as calcium carbonate and CPCs have a longer working time and low thermal effect. They are also biodegradable while providing good mechanical strength. However, the viscosity of injectable mineral cements is high, and the infiltration of these cements into the vertebral body has been questioned. Recently, the infiltration properties of CPC have been significantly improved, making it more suitable for injection into the vertebral bodies for vertebral reconstruction. Methods: Five patients were included in this open prospective study. Inclusion criteria were delayed collapsed vertebral compression fractures responsible for severe pain and neurologic dysfunction necessitating posterior decompression surgery. Of five patients, two were male and three were female with an average age at surgery of 80.4 years (71–85 years) and an average duration of follow-up of 2.5 years (2–3.5 years). Evaluation of clinical data was based on x-ray, Japanese Orthopaedic Association (JOA) score for low back pain (full score is 29 points), and Visual Analog Scale (VAS). Results: The levels of the delayed collapsed vertebrae were T10, L1, and L2 (for one patient each) and L4 (two patients). All patients were in poor condition, for example, renal failure, heart failure, and chronic hepatitis. The average operative time was 2 hours (1 hour 36 minutes to 2 hours 16 minutes), and intraoperative bleeding was 181 mL (85–236 mL). As for clinical symptoms, preoperative JOA score averaged 17.8 points and was improved to 26 points postoperatively, while the preoperative VAS score of 8.6 points improved to 2 points postoperatively. Morphologic evaluation showed preoperative vertebral compression ratio averaged 41% and improved to 74% immediately after the operation and finally settled at 68%. Just one of five cases experienced late vertebral collapse 3 months after the operation. Conclusion: Vertebral reconstruction with biodegradable CPC in the treatment of osteoporotic vertebral compression fracture using instrumentation was a safe and useful surgical treatment.

Nitric Oxide: A Possible Etiologic Factor in Spinal Cord Cavitation

To determine whether nitric oxide (NO) is related to spinal cord cavitation, we treated mice that underwent spinal cord injury with NG-mono-methyl-L-arginine (N-MMA). Spinal cord specimens were subjected to glial fibrillary acidic protein (GFAP) immunostaining, which is selective for astrocytes. Spinal cord cavities and GFAP-positive glial cells appeared simultaneously at 3 days after spinal cord injury, and the cavities enlarged at 7 days. In mice receiving N-MMA, the cavities were significantly smaller than those in the mice that underwent spinal cord injury only. However, the numbers of GFAP-positive cells showed no difference between these two groups. These experimental findings suggest that cavitation of the spinal cord is caused mainly by NO released from activated glial cells.