Yoshimoto Ishikawa

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.

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.

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.

A combination of keratan sulfate digestion and rehabilitation promotes anatomical plasticity after rat spinal cord injury

Functional recovery after neuronal injuries relies on neuronal network reconstruction which involves many repair processes, such as sealing of injured axon ends, axon regeneration/sprouting, and construction and refinement of synaptic connections. Chondroitin sulfate (CS) is a major inhibitor of axon regeneration/sprouting. It has been reported that the combination of task-specific rehabilitation and CS-digestion is much more effective than either treatment alone with regard to the promotion of functional and anatomical plasticity for dexterity in acute and chronic spinal cord injury models. We previously reported that keratan sulfate (KS) is another inhibitor and has a potency equal to CS. Here, we compared the effects of KS- or CS-digestion plus rehabilitation on recovery from spinal cord injury. Keratanase II or chondroitinase ABC was locally administered at the lesion after spinal cord injury at C3/4. Task-specific rehabilitation training, i.e., a single pellet reaching task using a Whishaw apparatus, was done for 3 weeks before injury, and then again at 1-6 weeks after injury. The combination of KS-digestion and rehabilitation yielded a better rate of pellet removal than either KS-digestion alone or rehabilitation alone, although these differences were not statistically significant. The combination of CS-digestion and rehabilitation showed similar results. Strikingly, both KS-digestion/rehabilitation and CS-digestion/rehabilitation showed significant increases in neurite growth in vivo as estimated by 5-hydroxytryptamine and GAP43 staining. Thus, KS-digestion and rehabilitation exerted a synergistic effect on anatomical plasticity, and this effect was comparable with that of CS-digestion/rehabilitation. KS-digestion might widen the therapeutic window of spinal cord injury if combined with rehabilitation.

Percutaneous Pedicle Screw Fixation of a Hangman's Fracture Using Intraoperative, Full Rotation, Three-dimensional Image (O-arm)-based Navigation: A Technical Case Report

Surgical treatment of a hangmans fractures is technically demanding, even when using the standard open procedure. In this case report, a type II hangmans fracture was treated by percutaneous posterior screw fixation, without a midline incision, using intraoperative, full rotation, three-dimensional (3D) image (O-arm)-based navigation. A 48-year-old woman was injured in a motor vehicle accident and diagnosed with a unilateral hangmans fracture associated with subluxation of the C2 vertebral body on C3. After attaching the reference arc of the 3D-imaging system to the headholder, the cervical spine was screened using an O-arm without anatomical registration. Drilling and screw fixation were performed using a guide tube while referring to the reconstructed 3D-anatomical views. The operation was successfully completed without technical difficulties or neurovascular complications. This percutaneous procedure requires less dissection of normal tissue, which may allow earlier recovery. However, further validation of this procedure for its effectiveness and safety is required.

Transcranial motor evoked potential waveform changes in corrective fusion for adolescent idiopathic scoliosis

OBJECTIVE Corrective surgery for spinal deformities can lead to neurological complications. Several reports have described spinal cord monitoring in surgery for spinal deformity, but only a few have included patients younger than 20 years with adolescent idiopathic scoliosis (AIS). The goal of this study was to evaluate the characteristics of cases with intraoperative transcranial motor evoked potential (Tc-MEP) waveform deterioration during posterior corrective fusion for AIS. METHODS A prospective database was reviewed, comprising 68 patients with AIS who were treated with posterior corrective fusion in a prospective database. A total of 864 muscles in the lower extremities were chosen for monitoring, and acceptable baseline responses were obtained from 819 muscles (95%). Intraoperative Tc-MEP waveform deterioration was defined as a decrease in intraoperative amplitude of ≥ 70% of the control waveform. Age, Cobb angle, flexibility, operative time, estimated blood loss (EBL), intraoperative body temperature, blood pressure, number of levels fused, and correction rate were examined in patients with and without waveform deterioration. RESULTS The patients (3 males and 65 females) had an average age of 14.4 years (range 11-19 years). The mean Cobb angles before and after surgery were 52.9° and 11.9°, respectively, giving a correction rate of 77.4%. Fourteen patients (20%) exhibited an intraoperative waveform change, and these occurred during incision (14%), after screw fixation (7%), during the rotation maneuver (64%), during placement of the second rod after the rotation maneuver (7%), and after intervertebral compression (7%). Most waveform changes recovered after decreased correction or rest. No patient had a motor deficit postoperatively. In multivariate analysis, EBL (OR 1.001, p = 0.085) and number of levels fused (OR 1.535, p = 0.045) were associated with waveform deterioration. CONCLUSIONS Waveform deterioration commonly occurred during rotation maneuvers and more frequently in patients with a larger preoperative Cobb angle. The significant relationships of EBL and number of levels fused with waveform deterioration suggest that these surgical invasions may be involved in waveform deterioration.

Radiographic Changes in Patients with Pseudarthrosis After Posterior Lumbar Interbody Arthrodesis Using Carbon Interbody Cages A Prospective Five-Year Study

BACKGROUND The aim of this study was to demonstrate longitudinal radiographic changes at up to five years in patients with pseudarthrosis after posterior lumbar interbody arthrodesis using carbon interbody cages. METHODS From 2003 to 2006, prospective longitudinal radiographic and CT (computed tomography) scan evaluations were made at up to five years after posterior lumbar interbody arthrodesis using carbon interbody cages at one or two levels in 153 consecutive patients. At the one-year evaluation, seventeen patients with early pseudarthrosis at nineteen levels were selected as subjects on the basis of one or more of the following characteristics: complete absence of osseous bridging between the upper and lower vertebrae, angular motion of ≥5°, and/or radiolucent zones surrounding the implant. Angular motion, continuity of osseous bridging, grafted bone quantity, and radiolucent zones around the pedicle screws and cages were observed annually until five years. RESULTS The mean angular motion of five levels that exhibited ≥5° of motion at one year began to decrease significantly thereafter (p = 0.046), and no level showed movement of ≥5° at five years. The mean grade of the radiolucent zones around the screws on CT showed significant improvements at two years (p = 0.039) and three years (p < 0.01). The radiolucent zones around the screws disappeared at twelve of sixteen levels by five years, and the radiolucent zones around the cages disappeared in eleven of seventeen levels by five years. Of eighteen levels with early pseudarthrosis, seven (39%) were assessed as successfully fused at three years and twelve (67%) at five years. Four (80%) of five patients with a radiolucent zone of >1 mm around the entire cage on CT at one year showed continuing pseudarthrosis at five years, whereas only two (15%) of thirteen patients without this finding did (crude relative risk = 5.2; 95% confidence interval, 1.35 to 20.02). A radiolucent zone of >1 mm around the entire cage on CT at one year could be an early predictor of permanent pseudarthrosis (odds ratio = 123; 95% confidence interval, 1.03 to 14,680). CONCLUSIONS The interbody arthrodesis site in patients with early pseudarthrosis may begin to change to a successful fusion one or two years after surgery, with two-thirds of such patients exhibiting successful fusion five years after surgery. Final assessment of pseudarthrosis should be performed at least three years after surgery. A radiolucent zone of >1 mm around the entire interbody cage on CT at one year may require early additional surgery. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Resection of Beak-Type Thoracic Ossification of the Posterior Longitudinal Ligament from a Posterior Approach under Intraoperative Neurophysiological Monitoring for Paralysis after Posterior Decompression and Fusion Surgery

Study Design Prospective clinical study. Objective Posterior decompression and fusion surgery for beak-type thoracic ossification of the posterior longitudinal ligament (T-OPLL) generally has a favorable outcome. However, some patients require additional surgery for postoperative severe paralysis, a condition that is inadequately discussed in the literature. The objective of this study was to describe the efficacy of a procedure we refer to as “resection at an anterior site of the spinal cord from a posterior approach” (RASPA) for severely paralyzed patients after posterior decompression and fusion surgery for beak-type T-OPLL. Methods Among 58 consecutive patients who underwent posterior decompression and fusion surgery for beak-type T-OPLL since 1999, 3 with postoperative paralysis (5%) underwent RASPA in our institute. Clinical records, the Japanese Orthopaedic Association score, gait status, intraoperative neurophysiological monitoring (IONM) findings, and complications were evaluated in these cases. Results All three patients experienced a postoperative decline in Manual Muscle Test (MMT) scores of 0 to 2 after the first surgery. RASPA was performed 3 weeks after the first surgery. All patients showed gradual improvements in MMT scores for the lower extremity and in ambulatory status; all could walk with a cane at an average of 4 months following RASPA surgery. There were no postoperative complications. Conclusions RASPA surgery for beak-type T-OPLL after posterior decompression and fusion surgery resulted in good functional outcomes as a salvage surgery for patients with severe paralysis. Advantages of RASPA include a wide working space, no spinal cord retraction, and additional decompression at levels without T-OPLL resection and spinal cord shortening after additional dekyphosis and compression maneuvers. When used with IONM, this procedure may help avoid permanent postoperative paralysis.