Zenya Ito

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.

Comparison of surgical outcomes between macro discectomy and micro discectomy for lumbar disc herniation: a prospective randomized study with surgery performed by the same spine surgeon.

Study Design A prospective study was conducted on the surgical procedures for lumbar disc herniation. Objective The objective of this study is to investigate the surgical outcomes of different methods when performed by the same surgeon, using a prospective study. Background Macro discectomy is widely known as a common surgical procedure for lumbar disc herniation, while microdiscectomy in place of Caspar technique (the Caspar method) and microendoscopic discectomy by a posterior approach are reported as less invasive surgical methods for this condition. However, there have not been a significant number of prospective studies conducted to compare different surgical procedures for lumbar disc herniation. Materials and Methods The target of our study was a group of 62 patients (male: 43, female: 19) who underwent surgery by macro discectomy (A group) and 57 patients (male: 33, female: 24) who underwent surgery by microdiscectomy in place of Caspar technique (B group). The mean ages at surgery were 34 (14 to 62) years and 41 (18 to 65) years respectively, and the mean duration of follow-up was 2 years and 8 months (12 months to 4 years). For all patients, the surgery was performed by 1 of the authors. The items investigated were the operation time, amount of bleeding, duration of hospitalization, amount of analgesic agent used after surgery, pre- and postoperative scores based on judgment criteria for treatment of lumbar spine disorders established by the Japanese Orthopaedic Association score, visual analog scales (VAS, 0 to 10) for lumbago before surgery and at discharge, VAS for sciatica before surgery and at discharge, perioperative complications, and cases requiring further surgery. Results There were no significant differences between the 2 surgical procedures in the frequency of use of an analgesic agent after surgery, the pre- and postoperative Japanese Orthopaedic Association scores or postoperative VAS for sciatica. Statistically significant differences were observed in the operation time, amount of bleeding, duration of hospitalization, and postoperative VAS for lumbar pain, but the differences were not large, and may not have been clinically significant. Conclusions For herniotomy for lumbar disc herniation, both macro discectomy and microdiscectomy are appropriate, as long as surgeons have mastery of the procedures.

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.

Laminoplasty and skip laminectomy for cervical compressive myelopathy: range of motion, postoperative neck pain, and surgical outcomes in a randomized prospective study.

Study Design. A prospective randomized clinical trial in surgical treatment for cervical compressive myelopathy. Objective. We prospectively compared modified laminoplasty and skip laminectomy in terms of surgical invasiveness, postoperative range of cervical motion, axial pain, and surgical outcomes. Summary of Background Data. Laminoplasty is an established procedure for the decompression of multisegmental cervical compressive myelopathy. However, it often induces postoperative problems, such as axial pain, restriction of neck motion, and loss of lordotic alignment. Skip laminectomy was recently developed as a minimally invasive procedure. Methods. Forty-one patients with cervical spondylotic myelopathy (CSM), excluding developmental stenosis, were randomized to modified double-door laminoplasty (Lamino group; n = 21) or skip laminectomy (Skip group; n = 20), and followed for more than 1 year (average, 28.1 months). Of these patients, radiographs were taken in neutral, extension, and flexion positions before surgery and after surgery. The cervical alignment of C2–C7 curvature and range of motion (ROM) were calculated. After surgery patients were asked to rate their neck pain, using the visual analogue scale (VAS) periodically. Clinical outcomes were estimated with the Japanese Orthopedic Association scoring system (JOA score). Results. There was no significant difference about operative time and blood loss between Lamino and Skip groups. The C2–C7 lordosis of neutral position in both groups was decreased by a few degrees at final follow-up. The final ROMs were 77.4/88.6% of preoperative ROM, respectively. At all collection times, no significant difference in VAS score of axial pain was seen in either group. There was no significant difference in JOA score between both groups before and after surgery. Conclusion. No significant differences were seen between Lamino and Skip groups, in terms of operative invasiveness, axial neck pain, cervical alignment, and ROM, and clinical results in the patients of CSM without developmental stenosis.

Segmental pedicle screwing for idiopathic scoliosis using computer-assisted surgery.

Study Design Retrospective clinical study. Objectives To evaluate the accuracy of computer-assisted surgery for idiopathic scoliosis. Summary of Background Data Segmental pedicle screw fixation has been proven to enable enhanced correction of scoliotic deformities. However, both neurovascular and visceral structures are at potential risk from screw misplacement due to pedicle drift. No reports exist on the accuracy and benefits of computer-assisted surgery for pedicle screwing in scoliosis surgery. Methods A total of 40 consecutive patients with idiopathic scoliosis were evaluated. Postoperative computed tomography was assessed for the accuracy of pedicle screw placement in 20 cases treated without a navigation system and 20 cases with a computed tomography-based navigation system. Correlations between registered levels and pedicle perforation were investigated. Results Pedicle violation was observed in 28.0% of the control group and 11.4% of the navigation group, with significant differences. No screw misplacements at the registered levels were seen, and the longer the distance between the registered level and level of screw insertion, the higher the rate of pedicle violation. No intraoperative complications caused by pedicle perforation occurred. Conclusions In the navigation group, a tendency to lateral perforation at the concave side and medial perforation at the convex side was noted, like in the control group. Use of the navigation system significantly reduced the screw misplacement rate for rotated vertebrae as compared with the control group. Separate registration is recommended for rotated vertebrae when possible.

Keratan Sulfate Restricts Neural Plasticity after Spinal Cord Injury

Chondroitin sulfate (CS) proteoglycans are strong inhibitors of structural rearrangement after injuries of the adult CNS. In addition to CS chains, keratan sulfate (KS) chains are also covalently attached to some proteoglycans. CS and KS sometimes share the same core protein, but exist as independent sugar chains. However, the biological significance of KS remains elusive. Here, we addressed the question of whether KS is involved in plasticity after spinal cord injury. Keratanase II (K-II) specifically degraded KS, i.e., not CS, in vivo. This enzyme digestion promoted the recovery of motor and sensory function after spinal cord injury in rats. Consistent with this, axonal regeneration/sprouting was enhanced in K-II-treated rats. K-II and the CS-degrading enzyme chondroitinase ABC exerted comparable effects in vivo and in vitro. However, these two enzymes worked neither additively nor synergistically. These data and further in vitro studies involving artificial proteoglycans (KS/CS-albumin) and heat-denatured or reduced/alkylated proteoglycans suggested that all three components of the proteoglycan moiety, i.e., the core protein, CS chains, and KS chains, were required for the inhibitory activity of proteoglycans. We conclude that KS is essential for, and has an impact comparable to that of CS on, postinjury plasticity. Our study also established that KS and CS are independent requirements for the proteoglycan-mediated inhibition of axonal regeneration/sprouting.

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.

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.

Postoperative changes in spinal cord signal intensity in patients with cervical compression myelopathy: comparison between preoperative and postoperative magnetic resonance images

OBJECT Increased signal intensity of the spinal cord on magnetic resonance (MR) imaging was classified pre- and postoperatively in patients with cervical compressive myelopathy. It was investigated whether postoperative classification and alterations of increased signal intensity could reflect the postoperative severity of symptoms and surgical outcomes. METHODS One hundred and four patients with cervical compressive myelopathy were prospectively enrolled. All were treated using cervical expansive laminoplasty. Magnetic resonance imaging was performed in all patients preoperatively and after an average of 39.7 months postoperatively (range 12-90 months). Increased signal intensity of the spinal cord was divided into 3 grades based on sagittal T2-weighted MR images as follows: Grade 0, none; Grade 1, light (obscure); and Grade 2, intense (bright). The severity of myelopathy was evaluated according to the Japanese Orthopedic Association (JOA) score for cervical myelopathy and its recovery rate (100% = full recovery). RESULTS Increased signal intensity was seen in 83% of cases preoperatively and in 70% postoperatively. Preoperatively, there were 18 patients with Grade 0 increased signal intensity, 49 with Grade 1, and 37 with Grade 2; postoperatively, there were 31 with Grade 0, 31 with Grade 1, and 42 with Grade 2. The respective postoperative JOA scores and recovery rates (%) were 13.9/56.7% in patients with postoperative Grade 0, 13.2/50.7% in those with Grade 1, and 12.8/40.1% in those with Grade 2, and these differences were not statistically significant. The postoperative increased signal intensity grade was improved in 16 patients, worsened in 8, and unchanged in 80 (77%). There was no significant correlation between the alterations of increased signal intensity and surgical outcomes. CONCLUSIONS The postoperative increased signal intensity classification reflected postoperative symptomatology and surgical outcomes to some extent, without statistically significant differences. The alteration of increased signal intensity was seen postoperatively in 24 patients (23%) and was not correlated with surgical outcome.

A genome-wide association study identifies susceptibility loci for ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is a common spinal disorder among the elderly that causes myelopathy and radiculopathy. To identify genetic factors for OPLL, we performed a genome-wide association study (GWAS) in ∼8,000 individuals followed by a replication study using an additional ∼7,000 individuals. We identified six susceptibility loci for OPLL: 20p12.3 (rs2423294: P = 1.10 × 10−13), 8q23.1 (rs374810: P = 1.88 × 10−13), 12p11.22 (rs1979679: P = 4.34 × 10−12), 12p12.2 (rs11045000: P = 2.95 × 10−11), 8q23.3 (rs13279799: P = 1.28 × 10−10) and 6p21.1 (rs927485: P = 9.40 × 10−9). Analyses of gene expression in and around the loci suggested that several genes are involved in OPLL etiology through membranous and/or endochondral ossification processes. Our results bring new insight to the etiology of OPLL.