Masatoshi Sumi

Postoperative lumbar spinal instability occurring or progressing secondary to laminectomy.

The manifestations and pathomechanism of postoperative lumbar spinal instability, occurring or progressing secondary to laminectomy, was clarified by means of functional radiographic analysis in a series of 46 patients over 40 years of age. The relation between instability and the clinical symptoms also is discussed. In patients under 60 years of age, instability at the operated level tended to appear in cases of wide laminectomy more often than in cases of partial laminectomy. Occurrence or progress of instability seems to be promoted by resection of the posterior spinal elements rather than the disc. It is further considered that the postoperative aggravation of clinical symptoms may be influenced not only by instability, but also by the other factors.

Total sacrectomy and reconstruction for sacral tumors.

Study Design. Report of three patients in whom the lumbosacral junctions were successfully restored by spinal instrumentations after total sacrectomies. Objectives. To describe the surgical technique of the reconstruction of the continuity between the pelvic ring and spinal column by using a transpedicular and iliac screw system. Summary of Background Data. Although there have been case reports about reconstruction methods after total sacrectomy, biomechanical, and technical problems still remain unresolved. Methods. Total sacrectomy was carried out in three cases: two with chordomas and one with a recurrent giant cell tumor. In the first case, reconstruction was achieved with Zielke transpedicular screw and rod system and a sacral rod. The other two patients were reconstructed using a transpedicular and iliac screw system and a sacral rod for bilateral fixation of the iliac wings. In the third patient, the vertical rods were connected to transverse rod with rod connectors. Results. No instrumentation failure was observed, and the continuity between the pelvic wing and spinal column was established with the instrumentation and bone grafting. Although one patient died of metastatic chordoma, the lumbosacral junction was successfully reconstructed with the instrumentation. The other two patients could stand with double crutches 13 and 2 years after surgery, respectively. Conclusions. Total sacrectomy is a feasible operation for primary malignant tumors involving the entire sacrum. Reconstruction of the union between the lumbar spine and the ilia with spinal instrumentation achieves stabilization suitable for ambulation.

Pathomechanism, pathogenesis, and results of treatment in cervical spondylotic myelopathy caused by dynamic canal stenosis

In this study, the pathomechanism and pathogenesis of dynamic canal stenosis caused by cervical instability in patients with cervical spondylotic myelopathy and the validity of the concept of instability are clarified by analyzing the results of treatment in 53 cases. In cases of cervical spondylotic myelopathy caused by dynamic canal stenosis, the authors found that the posterior slide of the vertebral body occurs as a result of degeneration in the cervical spine due to aging changes, and that the dynamic sagittal diameter of the spinal canal decreases with an increase of the degree of posterior slide. This is followed by gradual aggravation of the clinical symptoms. Continuous cervical traction was found to be the first choice of treatment. Surgical treatment is indicated in cases in which the traction was ineffective, or even when it was effective, in cases in which the Japanese Orthopaedic Association (JOA) score remained low or when there was a tendency toward rapid aggravation of symptoms. It was demonstrated that the shorter the duration of the myelopathy, the better the results of treatment obtained. A limit of the dynamic sagittal diameter of the spinal canal of 12 mm was considered as valid.

Effects of Cyclic Mechanical Stress on the Production of Inflammatory Agents by Nucleus Pulposus and Anulus Fibrosus Derived Cells In Vitro

Study Design. Cyclic mechanical stress (CMS) was applied to cultured nucleus pulposus and anulus fibrosus cells, and the production of inflammatory agents by these cells was evaluated. Objective. To investigate the involvement of CMS in the production of inflammatory agents by disc cells. Summary of Background Data. It has been reported that CMS affects degeneration of the disc. However, little is known about the effect of CMS on the production of inflammatory agents by both cell types in vitro. Methods. Cells derived from nucleus pulposus and anulus fibrosus of Sprague-Dawley rat tails were cultured with or without CMS applied by the Flexercell Strain Unit (Flexcell International Corp., Hillsborough, NC) in the presence or absence of inflammatory stimulus. Doses of prostaglandin-E2 (PGE2) were measured in the culture supernatants. Semiquantitative evaluations of the expressions of cyclooxygenase (COX)-2 and phospholipase-A2 IIA messenger ribonucleic acids (mRNAs) were also examined. Results. Sole application of CMS on nucleus pulposus and anulus fibrosus cells increased PGE2 synthesis. Coincidence of CMS and inflammatory stimulus synergistically enhanced PGE2 synthesis of both cell types. Anulus fibrosus cells showed a stronger reactivity to these stimuli than nucleus pulposus cells. The expression of COX-2 mRNA of anulus fibrosus cells tended to correlate to the amount of PGE2, whereas COX-2 mRNA was constitutively expressed in nucleus pulposus cells, suggesting that the roles of COX-2 might be different between nucleus pulposus and anulus fibrosus. Phospholipase-A2 IIA mRNA was constitutively expressed in both cell types. Conclusions. The results of this study suggested that CMS might be involved in the pathomechanism of pain induction of lumbar disc diseases.

Prognostic factors for deterioration of patients with cervical spondylotic myelopathy after nonsurgical treatment.

Study Design. A prospective study involving 56 patients with cervical spondylotic myelopathy (CSM) was conducted. Objective. To investigate the outcomes and prognostic factors for CSM after nonsurgical treatment. Summary of Background Data. The superiority of surgical treatment over nonsurgical treatment has not been confirmed in mild forms of CSM. Outcomes and prognostic factors for nonsurgical treatment of mild forms of CSM are not well understood. Methods. Clinical signs and symptoms of CSM were assessed by Japanese Orthopedic Association (JOA) scores. Nonsurgical treatment was selected for patients with mild forms of CSM (JOA ≥13 patients). Seventy patients with mild forms of CSM were enrolled in the study between 1995 and 2003. The follow-up rate was 80.0%. Prognostic factors that exacerbate clinical symptoms of CSM were examined, such as age, gender, follow-up period, developmental or dynamic factors on plain lateral radiograph, high signal intensity area on T2-weighted sagittal MRI, and the extent of maximum cord compression; partial or circumferential spinal cord compression, on axial MRI. Univariate and multivariate logistic regression analysis were carried out to test for significant prognostic factors. Results. There was, on average, no statistically significant deterioration in JOA scores after nonsurgical treatment. However, 11 of 56 patients deteriorated after nonsurgical treatment. The only factor that significantly exacerbated clinical symptoms of CSM was circumferential spinal cord compression in the maximum compression segment on axial MRI. Indeed, 10 of 33 CSM patients with circumferential spinal cord compression on axial MRI deteriorated after nonsurgical treatment. Conclusion. Outcomes of mild forms of CSM during nonsurgical treatment were generally good as shown by average JOA scores. The only prognostic factor for mild forms of CSM was circumferential spinal cord compression in the maximum compression segment on axial MRI. Surgical treatment can be considered for patients with this prognostic factor.

Multistep pedicle screw insertion procedure with patient-specific lamina fit-and-lock templates for the thoracic spine: clinical article.

OBJECT Pedicle screw fixation is a standard procedure of spinal instrumentation, but accurate screw placement is essential to avoid injury to the adjacent structures, such as the vessels, nerves, and viscera. The authors recently developed an intraoperative screw guiding method in which patient-specific laminar templates were used, and verified the accuracy of the multistep procedure in the thoracic spine. METHODS Preoperative bone images of the CT scans were analyzed using 3D/multiplanar imaging software and the trajectories of the screws were planned. Plastic templates with screw guiding structures were created for each lamina by using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Plastic vertebra models were also generated and preoperative screw insertion simulation was performed. Surgery was performed using this patient-specific screw guide template system, and the placement of screws was postoperatively evaluated using CT scanning. RESULTS Ten patients with thoracic or cervicothoracic pathological entities were selected to verify this novel procedure. Fifty-eight pedicle screws were placed using the screw guide template system. Preoperatively, each template was found to fit exactly and to lock on the lamina of the vertebra models, and screw insertion simulation was successfully performed. Intraoperatively the templates also fit and locked on the patient lamina, and screw insertion was completed successfully. Postoperative CT scans confirmed that no screws violated the cortex of the pedicles, and the mean deviation of the screws from the planned trajectories was 0.87 ± 0.34 mm at the coronal midpoint section of the pedicles. CONCLUSIONS The multistep, patient-specific screw guide template system is useful for intraoperative pedicle screw navigation in the thoracic spine. This simple and economical method can improve the accuracy of pedicle screw insertion and reduce the operating time and radiation exposure of spinal fixation surgery.

Prospective study and multivariate analysis of the incidence of C5 palsy after cervical laminoplasty.

Study Design. A prospective comparative study about the incidence of postoperative C5 palsy and multivariate analysis of the risk factors of C5 palsy. Objective. To clarify the risk factors of occurrence of C5 palsy after laminoplasty (LP) by comparing the 2 surgical procedures of open-door and double-door LP prospectively. Summary of Background Data. The incidence of C5 palsy has been reported to average 4.6%, and there has been no difference of the incidence among surgical procedures. However, there were only indirect retrospective studies. Methods. A total of 146 patients who underwent the LP procedure between 2006 and 2007 were studied prospectively. In 2006, the patients were assigned to undergo the open-door LP, and in 2007, they were assigned to undergo the double-door LP. The incidence of postoperative C5 palsy was compared prospectively between these 2 LP procedures, and the risk factors of C5 palsy were detected with multivariate logistic regression analysis. Results. Postoperative C5 palsy occurred in 7 of 73 cases after open-door LP (9.6%) and in 1 of 73 cases after double-door LP (1.4%). The incidence of C5 palsy after open-door LP was statistically higher than the one after double-door LP (P = 0.029), and open-door LP was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 69.6, P = 0.043). In addition, ossification of posterior longitudinal ligament (OPLL) was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 43.8, P = 0.048). Conclusion. This study showed significant evidence indicating the higher risk of postoperative C5 palsy in open-door LP than double-door LP. Because OPLL as well as open-door LP were recognized as the risk factors of C5 palsy, asymmetric decompression by open-door LP might introduce imbalanced rotational movement of spinal cord and result in C5 palsy. We recommend double-door LP to minimize the postoperative C5 palsy, in particularly, if the patient has OPLL.

Safe and accurate midcervical pedicle screw insertion procedure with the patient-specific screw guide template system.

Study Design. Clinical trial for midcervical pedicle screw insertion using a novel patient-specific intraoperative screw guiding device. Objective. To evaluate the availability of the “Screw Guide Template” (SGT) system for insertion of midcervical pedicle screws. Summary of Background Data. Despite many efforts for accurate midcervical pedicle screw insertion, there still remain unacceptable rate of screw malpositioning that might cause neurovascular injuries. We developed patient-specific SGT system for safe and accurate intraoperative screw navigation tool and have reported its availability for the screw insertion to C2 vertebra and thoracic spine. Methods. Preoperatively, the bone image on computed tomography was analyzed and the trajectories of the screws were designed in 3-dimensional format. Three types of templates were created for each lamina: location template, drill guide template, and screw guide template. During the operations, after engaging the templates directly with the laminae, drilling, tapping, and screwing were performed with each template. We placed 80 midcervical pedicle screws for 20 patients. The accuracy and safety of the screw insertion by SGT system were evaluated using postoperative computed tomographic scan by calculation of screw deviation from the preplanned trajectory and evaluation of screw breach of pedicle wall. Results. All templates fitted the laminae and screw navigation procedures proceeded uneventfully. All screws were inserted accurately with the mean screw deviation from planned trajectory of 0.29 ± 0.31 mm and no neurovascular complication was experienced. Conclusion. We demonstrated that our SGT system could support the precise screw insertion in midcervical pedicle. SGT prescribes the safe screw trajectory in a 3-dimensional manner and the templates fit and lock directly to the target laminae, which prevents screwing error along with the change of spinal alignment during the surgery. These advantages of the SGT system guarantee the high accuracy in screw insertion, which allowed surgeons to insert cervical pedicle screws safely. Level of Evidence: 3

The prognosis of conservative treatments for lumbar spinal stenosis: analysis of patients over 70 years of age.

Study Design. A prospective study. Objectives. To identify outcomes of aged patients with lumbar spinal stenosis (LSS) treated conservatively and to examine factors that control the prognosis. Summary and Background Data. There have been no reports evaluating the outcomes of conservative treatments for elderly LSS patients. Methods. A total of 89 patients, 70 years of age and older, who underwent in-hospital conservative treatment were included. The Japanese Orthopedic Association’s score (JOA score) and the disturbance level of activities of daily living (ADL) were used for evaluation. Nerve involvement was classified into radicular, cauda equina, and mixed type. Myelographic findings were classified into central defect with or without block and root defect. Associations between disturbance level of ADL, nerve involvement, and myelographic classifications were investigated. Results. The mean JOA score increased from 11.1 points at admission to 15.9 points at discharge, with 14.3 points maintained at the follow-up; 48.8% of radicular type showed no obstacle in ADL at the follow-up compared with 33.3% of the other types; 13.3% of central defect with block showed no obstacle in ADL compared with 47.8% of the other types with significant difference. Conclusion. The prognosis of conservative treatment for aged LSS was relatively good. Radicular type may be a candidate for conservative treatment. However, patients with complete block in the myelogram may not respond favorably to conservative treatment.

Progression of Cervical Spine Instabilities in Rheumatoid Arthritis : A Prospective Cohort Study of Outpatients over 5 Years

Study Design. A 5-year prospective cohort study of cervical spine instabilities in rheumatoid arthritis (RA). Objective. To clarify the natural course of cervical instabilities in RA patients and to determine predictors for the prognosis of RA cervical spine. Summary of Background Data. Although several previous studies investigating the natural history of RA cervical spine have been reported, few of them have described radiological predictive factors for the aggravation of these instabilities. Methods. Two hundred sixty-seven outpatients with “definite” or “classical” RA initially assigned were prospectively followed for over 5 years. Radiographic cervical findings were classified into three representative instabilities: atlantoaxial subluxation (AAS), vertical subluxation (VS), and subaxial subluxation (SAS). The aggravations of these instabilities were identified in the cases with a decrease of at least 2 mm in the Ranawat value of VS, an increase of at least 1 mm in translation of SAS, or a new development of respective instabilities. RA stages and mutilating changes were assessed in the hand radiograms. Results. Fifty-two point four percent of 267 patients, without any cervical instability at the beginning of follow-up, decreased to 29.6% at the end (P < 0.01), whereas VS and SAS increased significantly (P < 0.01). The aggravation of VS was observed at statistically higher rates in patients with pre-existing instabilities as follows; 25.7% of AAS (P = 0.01), 49.1% of VS (P < 0.01), and 41.2% of SAS (P = 0.06). The aggravation of SAS was also detected in 47.2% of VS and 64.7% of SAS (P < 0.01). Patients with pre-existing mutilating changes exhibited the aggravations of VS and SAS in significantly higher incidences (P < 0.01). Furthermore, the cases with development into mutilating changes during the follow-up showed significantly higher tendencies for the aggravations of these instabilities (P < 0.01). Conclusion. The incidences of VS and SAS significantly increased during the minimum 5-year follow-up. Prognostic factors of these instabilities were revealed to be the initial radiological findings of VS, SAS, and mutilating changes.