Akio Muramoto

Clinical accuracy of three-dimensional fluoroscopy-based computer-assisted cervical pedicle screw placement: a retrospective comparative study of conventional versus computer-assisted cervical pedicle screw placement.

OBJECT The authors performed a retrospective clinical study to evaluate the feasibility and accuracy of cervical pedicle screw (CPS) placement using 3D fluoroscopy-based navigation (3D FN). METHODS The study involved 62 consecutive patients undergoing posterior stabilization of the cervical spine between 2003 and 2008. Thirty patients (126 screws) were treated using conventional techniques (CVTs) with a lateral fluoroscopic view, whereas 32 patients (150 screws) were treated using 3D FN. Screw positions were classified into 4 grades based on the pedicle wall perforations observed on postoperative CT. RESULTS The prevalence of perforations in the CVT group was 27% (34 screws): 92 (73.0%), 12 (9.5%), 6 (4.8%), and 16 (12.7%) for Grade 0 (no perforation), Grade 1 (perforation < 1 mm), Grade 2 (perforation ≥ 1 and < 2 mm), and Grade 3 (perforation ≥ 2 mm), respectively. In the 3D FN group, the prevalence of perforations was 18.7% (28 screws): 122 (81.3%), 17 (11.3%), 6 (4%), and 5 (3.3%) for Grades 0, 1, 2, and 3, respectively. Statistical analysis showed no significant difference in the prevalence of Grade 1 or higher perforations between the CVT and 3D FN groups. A higher prevalence of malpositioned CPSs was seen in Grade 2 or higher (17.5% vs 7.3%, p < 0.05) in the 3D FN group and Grade 3 (12.7% vs 7.3%, p < 0.05) perforations in the CVT group. The ORs for CPS malpositioning in the CVT group were 2.72 (95% CI 1.16-6.39) in Grade 2 or higher perforations and 3.89 (95% CI 1.26-12.02) in Grade 3 perforations. CONCLUSIONS Three-dimensional fluoroscopy-based navigation can improve the accuracy of CPS insertion; however, severe CPS malpositioning that causes injury to the vertebral artery or neurological complications can occur even with 3D FN. Advanced techniques for the insertion of CPSs and the use of modified insertion devices can reduce the risk of a malpositioned CPS and provide increased safety.

Intraoperative, full-rotation, three-dimensional image (O-arm)–based navigation system for cervical pedicle screw insertion

OBJECT The aim of this study was to retrospectively evaluate the reliability and accuracy of cervical pedicle screw (CPS) placement using an intraoperative, full-rotation, 3D image (O-arm)-based navigation system and to assess the advantages and disadvantages of the system. METHODS The study involved 21 consecutive patients undergoing posterior stabilization surgery of the cervical spine between April and December 2009. The patients, in whom 108 CPSs had been inserted, underwent screw placement based on intraoperative 3D imaging and navigation using the O-arm system. Cervical pedicle screw positions were classified into 4 grades, according to pedicle-wall perforations, by using postoperative CT. RESULTS Of the 108 CPSs, 96 (88.9%) were classified as Grade 0 (no perforation), 9 (8.3%) as Grade 1 (perforations < 2 mm, CPS exposed, and < 50% of screw diameter outside the pedicle), and 3 (2.8%) as Grade 2 (perforations between ≥ 2 and < 4 mm, CPS breached the pedicle wall, and > 50% of screw diameter outside the pedicle). No screw was classified as Grade 3 (perforation > 4 mm, complete perforation). No neurovascular complications occurred because of CPS placement. CONCLUSIONS The O-arm offers high-resolution 2D or 3D images, facilitates accurate and safe CPS insertion with high-quality navigation, and provides other substantial benefits for cervical spinal instrumentation. Even with current optimized technology, however, CPS perforation cannot be completely prevented, with 8.3% instances of minor violations, which do not cause significant complications, and 2.8% instances of major pedicle violations, which may cause catastrophic complications. Therefore, a combination of intraoperative 3D image-based navigation with other techniques may result in more accurate CPS placement.

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.

S3-4. New alarm point of transcranial electrical stimulation motor evoked potentials for intraoperative spinal cord monitoring. A prospective multicenter study of the Spinal Cord Monitoring Working Group of the Japanese Society for Spine Surgery and Related Research (JSSR)

Transcranial electrical stimulation motor evoked potentials (TcMEPs) became the gold standard for intraoperative spinal cord monitoring. However there is no definite alarm point of TcMEPs due to a lack of multicenter study. Thus we set 70% decrease of amplitude as the alarm point of TcMEPs from the experience of our 48 true positive cases from 2007 to 2009. 959 cases of spinal deformity, spinal cord tumor and ossification of the posterior longitudinal ligament (OPLL) were included in this prospective multicenter study from our 18 institutes related to the Japanese Society for Spine Surgery and Related Research monitoring working group from 2010 to 2012. There were only two false negative cases which were intramedullary spinal cord tumor. This new alarm criterion provided higher sensitivity (95%) and specificity (91.1%) for intraoperative spinal cord monitoring and good accuracy except for intramedullary spinal cord tumor. This study is the first prospective multicenter research to investigate the alarm point of TcMEPs. We recommend the alarm point to be a 70% decrease of amplitude for routine spinal cord monitoring, especially in surgery for spinal deformity, OPLL and extramedullary spinal cord tumor.

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

CD44 expression in astrocytes and microglia is associated with ALS progression in a mouse model.

Amyotrophic lateral sclerosis (ALS) is a motor neuron-specific neurodegenerative disease. An increasing body of evidence suggests that, in addition to cell autonomous regulation, i.e., pathological changes in motor neurons, non-cell autonomous mechanisms involving glial cells play critical roles in the pathogenesis of ALS. CD44 functions as a receptor for osteopontin and hyaluronan, and has been implicated in inflammation associated with neuronal injuries. However, this membrane glycoprotein has been poorly studied in ALS. Here we investigated its expression during ALS progression using SOD1(G93A) mice. CD44 expression increased around the onset of disease and then increased continuously. Astrocytes and microglia expressed CD44 in vivo. Consistent with these findings, primary cultured microglia began to express CD44 upon activation with LPS and interferon-γ. CD44 expression in primary cultured astrocytes was also enhanced by activation with interferon-γ+TNF-α or bFGF alone. As CD44 was detected in cell lysate, but not in culture media of astrocytes and microglia, it was likely that these glial cells expressed a membrane-bound form of CD44. Our study demonstrates that CD44 expression in astrocytes and microglia is closely associated with the pathogenesis of ALS, and suggests that inflammatory responses involving CD44 may play a role in this disease.

Hyaluronan oligosaccharides promote functional recovery after spinal cord injury in rats

Hyaluronan is a component of the extracellular matrix of the central nervous system, and forms perineuronal nets around neurons. It has been recently reported that the hyaluronan-degrading enzyme hyaluronidase promotes lateral mobility of AMPA-type glutamate receptors and enhances synaptic plasticity. However, the biological significance of hyaluronan-degrading products (oligosaccharides) has not been studied in depth. Here we investigated the effects of hyaluronan oligosaccharides on motor function recovery after spinal cord injury in rats. The disaccharide HA2 and especially the tetrasaccharide HA4, significantly improved motor function, unlike the case with oligosaccharides composed of 6-12 saccharides. Consistent with this finding, HA4 treatment enhanced axonal regeneration/sprouting, as assessed by corticospinal tract tracer fiber counts. HA4 treatment also significantly suppressed accumulation of Iba-1-positive cells in a lesion two weeks after injury. In vitro experiments demonstrated that NMDA-induced neuronal cell death was partly blocked by HA4, but not by other oligosaccharides, whereas proteoglycan-mediated inhibition of neurite outgrowth was not affected by treatment with any oligosaccharide examined. Taken together, the present results revealed that due in part to its neuroprotective activity, HA4 promotes motor function recovery after spinal cord injury.

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.