Kei Ando

Bone union rate with autologous iliac bone versus local bone graft in posterior lumbar interbody fusion.

Study Design. A retrospective clinical study with a long-term follow-up in a single facility. Objective. The purpose of this study is to compare bone union rate between autologous iliac crest bone graft and local bone graft in patients treated by posterior lumbar interbody fusion (PLIF) using carbon cage for single-level interbody fusion. Summary of Background Data. Recently, a number of authors have reported on local bone grafting using bone that is obtained from laminectomy, and have indicated that the achieved fusion rate is similar to that of autologous iliac bone grafting. However, there is no report comparing the fusion rates between autologous iliac bone and local bone graft with a detailed follow-up of fusion progression. Methods. The subjects were 101 patients whose course could be observed for at least 2 years. The diagnosis was lumbar spinal canal stenosis in 14 patients, herniated lumbar disc in 19 patients, and degenerative spondylolisthesis in 68 patients. Single interbody PLIF was performed using iliac bone graft in 54 patients and local bone graft in 47 patients. Existence of pseudarthrosis on X-P (anteroposterior and lateral view) was investigated during the same follow-up period. Results. No significant differences were found in operation time and blood loss. Significant differences were also not observed in fusion grade at any follow-up period or in fusion progression between the 2 groups. Donor site pain continued for more than 3 months in 6 cases (11%). The final fusion rate was 94.5% versus 95.8%. Conclusion. Fusion results from the local bone group and the autologous iliac bone group were nearly identical. Furthermore, fusion progression was nearly identical. Complications at donor sites were seen in 17% of the cases. From the aforementioned results, it was concluded that local bone graft is as beneficial as autologous iliac bone graft for PLIF at a single level.

N-Acetylglucosamine 6-O-Sulfotransferase-1-Deficient Mice Show Better Functional Recovery after Spinal Cord Injury

Neurons in the adult CNS do not spontaneously regenerate after injuries. The glycosaminoglycan keratan sulfate is induced after spinal cord injury, but its biological significance is not well understood. Here we investigated the role of keratan sulfate in functional recovery after spinal cord injury, using mice deficient in N-acetylglucosamine 6-O-sulfotransferase-1 that lack 5D4-reactive keratan sulfate in the CNS. We made contusion injuries at the 10th thoracic level. Expressions of N-acetylglucosamine 6-O-sulfotransferase-1 and keratan sulfate were induced after injury in wild-type mice, but not in the deficient mice. The wild-type and deficient mice showed similar degrees of chondroitin sulfate induction and of CD11b-positive inflammatory cell recruitment. However, motor function recovery, as assessed by the footfall test, footprint test, and Basso mouse scale locomotor scoring, was significantly better in the deficient mice. Moreover, the deficient mice showed a restoration of neuromuscular system function below the lesion after electrical stimulation at the occipito-cervical area. In addition, axonal regrowth of both the corticospinal and raphespinal tracts was promoted in the deficient mice. In vitro assays using primary cerebellar granule neurons demonstrated that keratan sulfate proteoglycans were required for the proteoglycan-mediated inhibition of neurite outgrowth. These data collectively indicate that keratan sulfate expression is closely associated with functional disturbance after spinal cord injury. N-acetylglucosamine 6-O-sulfotransferase-1-deficient mice are a good model to investigate the roles of keratan sulfate in the CNS.

The cutoff amplitude of transcranial motor evoked potentials for transient postoperative motor deficits in intramedullary spinal cord tumor surgery.

Study Design. Retrospective clinical study of intraoperative transcranial motor evoked potential (TcMEP) amplitudes and postoperative motor deficits (PMDs). Objective. To determine the quantifiable cutoff amplitude of TcMEP for predicting transient PMDs in intramedullary spinal cord tumor (IMSCT) surgery. Summary of Background Data. The “presence or absence” criterion is reliable and widely used the alarm criterion for preventing permanent PMDs in IMSCT surgery. However, we wanted to prevent PMDs even if it is transient. The cutoff amplitude for transient PMDs should be identified. Methods. We conducted a retrospective study to identify the cutoff amplitude for predicting transient PMDs in IMSCT surgery. Thirty-seven patients were included in the study. We examined intraoperative electrophysiological changes and perioperative motor status in these patients. Receiver operating characteristic analyses were performed to identify the cutoff amplitudes for predicting transient PMDs in IMSCT surgery. The incidence of PMDs and cutoff TcMEP amplitude in cervical and thoracic lesions were compared. Results. Thirteen cases demonstrated transient PMDs. Among 280 monitorable muscles in 37 cases, 51 muscles in 13 patients showed PMDs. Through receiver operating characteristic analysis, the relative and the absolute cutoff amplitudes at the intraoperative point of deterioration were identified to be 12% residual of baseline amplitude and 3.2 &mgr;V, respectively. Sensitivity/specificity for those cutoff points are 86%/74% and 88%/78%, respectively. The incidence of PMD was significantly higher, and the cutoff amplitude was lower in the thoracic lesions than in the cervical lesions. Conclusion. We determined the cutoff TcMEP amplitude for predicting transient PMDs in IMSCT surgery. The cutoff amplitude for the cervical lesions was higher than that for the thoracic lesions. The results suggest the need for setting different alarm criteria in different level of spine. Level of Evidence: 3

The cutoff amplitude of transcranial motor-evoked potentials for predicting postoperative motor deficits in thoracic spine surgery.

Study Design. Prospective clinical study of intraoperative transcranial motor-evoked potentials (TcMEP) amplitudes and postoperative motor deficits. Objective. To determine the cutoff amplitude during intraoperative TcMEP monitoring for predicting postoperative motor deficits after thoracic spine surgery. Summary of Background Data. Several alarm points when monitoring with TcMEP have been advocated, but there have been no reports on an actual cutoff amplitude of TcMEP for predicting the occurrence of postoperative motor deficits. Methods. Among 80 consecutive surgical cases, 28 had a deterioration in TcMEP amplitude in at least 1 monitored muscle during surgery. We examined intraoperative electrophysiological changes and postoperative motor deficits in 270 monitorable muscles in those 28 patients. Through receiver operating characteristic curve analysis, we identified the cutoff amplitudes at the intraoperative point of deterioration and at the end of surgery for predicting postoperative motor deficits in both relative and absolute values. Results. The relative and the absolute cutoff amplitudes of TcMEP at the intraoperative point of deterioration and at the end of thoracic spine surgery were 12% of control amplitude and 1.9 &mgr;V and 25% of control amplitude and 3.6 &mgr;V, respectively. Sensitivity/specificity for those cutoff points are 88%/64%, 69%/83%, 90%/64%, and 70%/82%, respectively. Conclusion. We determined the cutoff amplitude for predicting postoperative motor deficits in thoracic spine surgery. The results may help establish the alarm criteria for thoracic spine surgery.

A new criterion for the alarm point for compound muscle action potentials.

OBJECT The purpose of this study was to review the present criteria for the compound muscle action potential (CMAP) alert and for safe spinal surgery. METHODS The authors conducted a retrospective study of 295 patients in whom spinal cord monitoring had been performed during spinal surgery. The waveforms observed during spinal surgery were divided into the following 4 grades: Grade 0, normal; Grade 1, amplitude decrease of 50% or more and latency delay of 10% or more; Grade 2, multiphase pattern; and Grade 3, loss of amplitude. Waveform grading, its relationship with postoperative motor deficit, and CMAP sensitivity and specificity were analyzed. Whenever any wave abnormality occurred, the surgeon was notified and the surgical procedures were temporarily suspended. If no improvements were seen, the surgery was terminated. RESULTS Compound muscle action potential wave changes occurred in 38.6% of cases. With Grade 1 or 2 changes, no paresis was detected. Postoperative motor deficits were seen in 8 patients, all with Grade 3 waveform changes. Among the 287 patients without postoperative motor deficits, CMAP changes were not seen in 181, with a specificity of 63%. The false-positive rate was 37% (106 of 287). However, when a Grade 2 change was set as the alarm point, sensitivity was 100% and specificity was 79.4%. The false-positive rate was 20% (59 of 295). CONCLUSIONS Neither the Grade 1 nor the Grade 2 groups included patients who demonstrated a motor deficit. All pareses occurred in cases showing a Grade 3 change. Therefore, the authors propose a Grade 2 change (multiphasic waveform) as a new alarm point. With the application of this criterion, the false-positive rate can be reduced to 20%.

Predictors of aggravation of cervical spine instability in rheumatoid arthritis patients: the large joint index

BackgroundImproved rheumatic drugs have provided significant benefits, but activities of daily living are not improved if spinal symptoms are overlooked. Furthermore, the appropriate timing for examining the cervical spine during follow-up is unclear.MethodsTo evaluate the relations of cervical spine instabilities and an index for cervical spine lesion in rheumatoid arthritis (RA) based on extremity radiographs, we examined preoperative radiographs of 100 RA patients who underwent total knee arthroplasty. Radiographic results for eight large joints (bilateral shoulders, elbows, hips, and knees) were graded as follows: Larsen grade ≥2 for each joint was scored as 1 point, which we refer to as the “large joint index” (LJI), based on 0–8 points. The associations of radiographic cervical lesions with LJI, Ranawat class, the disease duration, RA drugs, or blood analysis data were evaluated.ResultsAtlantoaxial subluxation (AAS) (≥5 mm) was found in 45 patients, vertical subluxation (VS) (≤13 mm) in 42, a posterior atlantodental interval (PADI) (<14 mm) in 21, and subaxial subluxation (SAS) (≥3 mm) in 23. Most patients with a PADI < 14 mm (19/21, 90%) were complicated with both AAS and VS. LJI had a significant association with AAS (P < 0.0001), VS (P < 0.01), and PADI (P < 0.01). The PADI was significantly lower (P < 0.0001) and the LJI was significantly higher (P < 0.01) in patients of Ranawat class II compared to patients of Ranawat class I. The disease duration, age at surgery, and age at onset were also significantly associated with cervical instabilities.ConclusionsPADI should be recognized as a predictor of paralysis with anteroposterior instability and vertical and middle-low cervical spine instability. The LJI proposed in this study has the possibility of being a predictor of cervical lesions. Patients with RA onset at a young age and a long disease duration also have a risk of progression of cervical spine instability.

Predictive factors for a poor surgical outcome with thoracic ossification of the ligamentum flavum by multivariate analysis: a multicenter study.

Study Design. Retrospective multi-institutional study. Objective. The purpose of this study was to describe the surgical outcomes in patients with ossification of the ligamentum flavum (OLF) and determine the influence of an ossified anterior longitudinal ligament (OALL) on the clinical features and surgical outcomes in thoracic OLF. Summary of Background Data. Detailed analyses of surgical outcomes of thoracic OLF have been difficult because of rarity of this disease. Methods. We identified 96 patients (77 males and 19 females with a mean age at surgery of 63.4 ± 10.3 yr) who underwent surgery for thoracic OLF and investigated their preoperative symptoms, severity of symptoms and myelopathy, disease duration, magnetic resonance imaging and computed tomographic findings, surgical procedure, intraoperative findings, and postoperative recoveries. The presence of OALL found at or near the most severely affected OLF level on sagittal computed tomographic images was classified into 1 of the following 4 types: (1) “no discernible type” (type N); (2) “one-sided type” (type O); (3) “discontinuous type” (type D); and (4) “continuous type” (type C). Multivariate logistic regression analysis was used to compute odds ratios and 95% confidence intervals to identify the risk factors associated with surgical outcomes. Results. The mean Japanese Orthopaedic Association score was 5.6 points preoperatively and 7.8 points 2 years postoperatively, yielding a mean recovery rate of 44.6%. Disease duration, presence of ossified dura mater, and type D OALL were the important factors for predicting surgical outcomes. Conclusion. After evaluating surgical outcomes on the largest sample size of OLF surgical procedures thus far, our results show that disease duration, ossification of the dura mater, and the presence of type D OALL were risk factors related to surgical outcomes. Level of Evidence: 3

Midkine overcomes neurite outgrowth inhibition of chondroitin sulfate proteoglycan without glial activation and promotes functional recovery after spinal cord injury

Injuries in the mammalian central nervous system induce a variety of factors which promote or inhibit neuronal axon regeneration/sprouting. However, the inhibitory activities are much stronger, and indeed are the major obstacle to functional recovery. Chondroitin sulfate proteoglycans (CSPGs) are produced by activated glial cells, and are among the strongest inhibitors. Here, we investigated the role of the growth factor midkine (MK), which binds to CSPGs, in neuronal injury. MK expression was induced by spinal cord injury, and was mainly produced by activated astrocytes. A prolonged culture of neurons also produced MK. MK not only enhanced neurite outgrowth on the substratum coated with poly-l-lysine, but also overcame the neurite growth inhibition by the CSPG substratum. Moreover, we found that MK activated neither astrocytes nor microglia as evaluated by morphological changes and cell proliferation or nitric oxide production. These properties would be advantageous for the treatment of neuronal injuries in vivo. Therefore, we next explored the therapeutic effect of MK in a rat spinal cord injury model. MK or vehicle was administered intrathecally for 2 weeks using an osmotic pump after spinal cord contusion injury. Rats treated with MK showed significantly better functional recovery after 5 weeks. These results suggest that MK may offer a potent alternative for the treatment of neuronal injuries without activating glial cells.

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.

Clinical Outcome of Treatments for Spinal Dural Arteriovenous Fistulas : Results of Multivariate Analysis and Review of the Literature

Study Design. This study was a case series study using a prospective single-institute database for the treatment of spinal dural arteriovenous fistulas (SDAVFs). Objective. To evaluate clinical factors that influence the neurological outcomes of treatment for SDAVFs, which were obtained from the analysis of 21 patients treated in our institution, and to provide management recommendations based on the review of former major clinical studies including our own reported over the past 2 decades. Summary of Background Data. Since 1977, when Kendall and Logue described the etiology of SDAVFs as hyperpressure of intrathecal veins due to an abnormal shunting from the arteries, treatment strategies have improved dramatically along with developments in neuroimaging, endovascular techniques and materials, and microsurgery based on the underlying pathophysiological process. However, therapeutic guidelines remain controversial. Methods. Patients treated for SDAVFs from 2000 to 2008 were eligible. Age, sex, level of shunting, initial symptom, duration of symptom, the treatment method, and clinical symptoms before and 6 months after treatment were investigated. Results. There were a total of 30 patients (18 male and 12 female), with a mean age of 59 years; 21 of them underwent treatment for the first time. We conducted a univariate analysis using a logistic regression model, on age, sex, the level of SDAVFs, duration of symptoms, symptom (sensory or paralysis), and gait function and micturition before treatment, and the intervention method were set as variables to investigate the risk factors for motor deficit 6 months after the treatment. Only gait function before treatment was correlated with the motor deficit 6 months after treatment (odds ratio = 10.0; 95% confidence interval = 1.28–78.11, P = 0.03). From these results, intervention at an early stage would be the key to a preferable outcome of the treatment for SDAVFs. Conclusion. The clinical status before treatment significantly influenced the clinical outcome after the treatment.