Naobumi Hosogane

Long-term surgical outcomes of spinal meningiomas

Study Design. Retrospective case series. Objective. To evaluate the treatment strategies for spinal meningioma. Summary of Background Data. Although previous studies have demonstrated favorable surgical outcomes for spinal meningioma, with a low incidence of tumor recurrence, few have examined long-term surgical outcomes. Methods. The influence of patient age, surgical margin status (Simpson grade), tumor location, and histological subtype on tumor recurrence were examined retrospectively. In addition, the resected dura mater from Simpson grade I cases was examined for invasive tumor cells and compared with the presence or absence of a dural tail sign on magnetic resonance image. Results. Complete resection (Simpson grades I and II) was performed in 62 patients. Among them, the tumor recurrence rate was 9.7%, all in patients who underwent grade II resection for ventral spinal lesions. The mean duration to reoperation in these patients was 12.2 ± 5.2 years. Of the 6 patients who underwent incomplete resection (Simpson grade III/IV), all required reoperation for tumor recurrence or regrowth, 5 years later on average. Patients younger than 50 years at the initial surgery had a significantly higher recurrence rate than those aged 50 years or older. Histologic examination of 43 dura mater specimens from Simpson grade I-resection patients revealed tumor cell invasion between the inner and outer layers in 15 patients. This invasion was noted in 8 (29%) of 28 patients who were negative for the dural tail sign on magnetic resonance image, and in 7 (47%) of 15 patients who showed a positive dural tail sign. The MIB-1 index reached about 10% for dumbbell-type meningiomas invading the vertebral body; these were associated with repeated recurrence and unfavorable prognosis. Conclusion. Long-term follow-up after surgery for meningiomas indicated that Simpson grade I resection should be selected whenever practicable when treating younger patients or dumbbell-type meningiomas. Tumors recurred at 12 years, on average, in approximately 30% of patients who underwent grade II resection.

Excessive reactive oxygen species are therapeutic targets for intervertebral disc degeneration

IntroductionOxidative stress has been reported to be involved in numerous human diseases, including musculoskeletal disorders such as osteoarthritis. However, the interaction between intervertebral disc (IVD) degeneration and oxidative stress is not well understood. The purpose of the present study was to elucidate the contribution of oxidative stress to IVD degeneration and the efficacy of antioxidant treatment for degenerative discs.MethodsThe expression level of an oxidative stress marker, nitrotyrosine, was assessed by immunohistochemistry and Western blotting. For evaluating intracellular reactive oxygen species (ROS) levels and oxidative stress in rat annulus fibrosus (AF) cells, flow cytometry and luciferase assay with an OKD48 construct were performed. The grade of IVD degeneration was assessed by magnetic resonance imaging and histological analysis.ResultsA high frequency of nitrotyrosine-positive cells was observed in rat and human degenerative discs. mRNA expression of catabolic factors such as tumor necrosis factor-alpha (TNF-alpha), matrix metalloprotease-3 (MMP-3), and cyclooxygenase-2 (COX-2) was significantly induced by treatment with H2O2 or buthionine sulfoximine, whereas that of aggrecan, an important chondrogenic proteoglycan, was reduced in a dose-dependent manner. Treatment with mitogen-activated protein kinase (MAPK) inhibitors blocked the inductive effect of excessive ROS on COX-2 mRNA expression. Western blotting confirmed the phosphorylation of MAPKs in H2O2 and BSO-treated AF cells. Conversely, we showed that TNF-α induced oxidative stress with increased intracellular ROS levels in AF cells. Treatment with the antioxidant N-acetyl cysteine (NAC) abrogated the catabolic effect of excessive ROS and TNF-alpha in vitro. Finally, we showed that oral administration of NAC prevented IVD degeneration in rat degenerative model.ConclusionsA positive feedback loop was formed between excessive ROS and TNF-alpha in AF cells. Thus, oxidative stress contributes to the progression of IVD degeneration and NAC can be a therapeutic option for IVD degeneration.

Postoperative distal adding-on and related factors in Lenke type 1A curve.

Study Design. A retrospective, multicenter study. Objective. To investigate the occurrence of and factors related to postoperative adding-on in Lenke type 1A curve. Summary of Background Data. Although several studies have investigated factors associated with adding-on in Lenke type 1A curve, these factors have not been elucidated in a large study population. Methods. This study included 112 patients who were followed more than 2 years after undergoing selective posterior thoracic fusion surgery for Lenke Type 1A curve (8 males, 104 females; mean age at surgery, 16.1 yr; mean follow-up, 3.6 yr). The lower instrumented vertebra (LIV) was T12 in 22 patients, L1 in 55, L2 in 32, and L3 in 3. Distal to the main thoracic curve, the end vertebra, neutral vertebra, stable vertebra (SV), and the last vertebra touching the central sacral vertical line (last touching vertebra, LTV) were determined. The occurrence and factors associated with distal adding-on were investigated. Results. The mean Cobb angle and apical translation of the main thoracic curve were 54.6° ± 9.6° and 53.1 ± 20.4 mm before surgery, and 14.2 ± 7.4 and 16.2 ± 12.7 at follow-up, respectively. Distal adding-on was observed in 21 patients (18.8%) at follow-up. Univariate analyses identified several factors significantly associated with adding-on, including the preoperative proximal thoracic curve, the apical translation of the main thoracic curve, Miyanjis subclassification, the postsurgical proximal and main thoracic curves, the postsurgical apical translation of the main thoracic curve, the correction rate of the main thoracic curve and the clavicle angle immediately after surgery and at follow-up, and the difference in levels between the LIV and the end vertebra, neutral vertebra, LTV, and stable vertebra. Logistic regression analysis showed that the apical translation of the main thoracic curve immediately after surgery (apical translation >25 mm, odds ratio: 10.7, 95% confidence interval: 3.1–37.0, P = 0.001) and the difference in levels between LIV and LTV (LIV-LTV) (LIV-LTV <0, odds ratio: 6.7, 95% confidence interval: 1.9–23.9, P = 0.003) were significantly associated with adding-on. Conclusion. Since the residual apical translation of the main thoracic curve and the lowest instrumented vertebra more cranial to the last touching vertebra were significantly associated with adding-on, surgeons may need to obtain the maximum reduction of the apical translation of the main thoracic curve and to extend the LIV at least to the LTV to avoid postoperative adding-on. Level of Evidence: N/A

Clinical significance of diffusion tensor tractography as a predictor of functional recovery after laminoplasty in patients with cervical compressive myelopathy.

OBJECT This study was conducted to determine whether postoperative changes in the fractional anisotropy (FA) value and diffusion tensor imaging of the cervical spinal cord can predict functional outcome for patients with cervical compressive myelopathy (CCM). METHODS Twenty patients with CCM were treated by laminoplasty from 2008 to 2009. Both T2-weighted MRI and diffusion tensor imaging were performed before and after surgery. The FA values were analyzed and fiber tracking was performed. The fiber tract (FT) ratio was calculated according to the following formula: (number of fibers at the compressed level)/(number of fibers at the C-2 level) × 100%. The Japanese Orthopaedic Association scoring system for cervical myelopathy was used to determine pre- and postoperative neurological status of the patients, and the Hirabayashi method was used to calculate the recovery rate. RESULTS There was no significant difference in recovery rates between patients with and those without intramedullary high signal intensity on preoperative T2-weighted images. Substantial differences in FA value among spinal cord, bone, and CSF made it difficult to obtain a precise FA value for the compressed spinal cord. There was a significant correlation between the preoperative FT ratio and the recovery rate (p = 0.0006). A poor outcome (recovery rate < 40%) could be anticipated for CCM patients with preoperative FT ratios below 60%. CONCLUSIONS The preoperative FT ratio correlated significantly with the recovery rates in CCM patients. Preoperative diffusion tensor tractography can be a new prognostic predictor for neurological recovery in CCM patients after laminoplasty.

Age-related changes in expression of tissue inhibitor of metalloproteinases-3 associated with transition from the notochordal nucleus pulposus to the fibrocartilaginous nucleus pulposus in rabbit intervertebral disc.

Study Design. Experimental study on age-related changes in expression of tissue inhibitor of metalloproteinases-3 (TIMP-3) associated with transition from notochordal nucleus pulposus (NP) to fibrocartilaginous NP in rabbit intervertebral disc (IVD). Objectives. To identify roles of notochordal NP in extracellular matrix (ECM) metabolism of IVD. Summary of Background Data. One of most interesting properties of TIMP-3 is to inhibit aggrecanases in addition to matrix metalloproteinases. Balance of aggrecanase/TIMP-3 is critical to maintain homeostasis of ECM metabolism. Methods. Four-week-old and 160-week-old male Japanese white rabbits were used. Age-related changes in IVDs were evaluated histologically using previously established grading system. Immunohistochemistry of TIMP-3 and semiquantitative reverse transcriptase-polymerase reaction (RT-PCR) of TIMP-3, a disintegrin and metalloproteinases with thrombospondin motifs (ADAMTS) 4, 5, and transforming growth factor-&bgr;1 (TGF-&bgr;1), were conducted. Results. Semiquantitative assessment of histologic changes indicated that 4-week-old rabbit was equivalent to fetus to 2-year-old human and 160-week-old rabbit was equivalent to 11- to 30-year-old human, particularly 11- to 16-year-old, which corresponds to transition period from notochordal to fibrocartilaginous NP. Immunohistochemistry revealed that TIMP-3 was positive in 4-week-old rabbit only. Semiquantitative RT-PCR revealed that levels of expressions of TGF-&bgr;1 and TIMP-3 mRNAs in 4-week-old were significantly higher than those in 160-week-old rabbits. There was no significant difference in expression of ADAMTS4 mRNA. ADAMTS5 mRNA was not detected or extremely low in both groups. Expression of TIMP-3 mRNA in NP was upregulated by TGF-&bgr;1 but was not affected by IL-1&bgr;. On the contrary, expression of ADAMTS4 mRNA was not upregulated by TGF-&bgr;1 but was upregulated by IL-1&bgr;. Conclusions. Levels of expression of TIMP-3 in notochordal NP were significantly lower in 160-week-old rabbits than those in 4-week-old rabbits. Decrease in expression of TIMP-3, possibly mediated in part by TGF-&bgr;1, may cause imbalance of ADAMTS4/TIMP-3 ratio at transition period from notochordal to fibrocartilaginous NP.

Impact of lamina closure on long-term outcomes of open-door laminoplasty in patients with cervical myelopathy: minimum 5-year follow-up study.

Study Design. A prospective follow-up study. Objective. To elucidate the impact of lamina closure on long-term outcomes after open-door laminoplasty. Summary of Background Data. In a previous study, we did not find significant associations between lamina closure and short-term outcomes. Methods. Of the original cohort of 82 patients who underwent open-door laminoplasty, 69 were included in this study (52 men, 17 women; mean age, 60.9 yr; mean follow-up, 6.2 yr; 56 with spondylosis or disc herniation, 13 with ossification of posterior longitudinal ligament). Lamina closure was previously observed in 23 of these patients (closure group) but not in 46 (nonclosure group). The Japanese Orthopaedic Association (JOA) scores and Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire were recorded. Results. The JOA score was 9.9 ± 3.2 in the closure group and 11.2 ± 2.3 in the nonclosure group before surgery (P = 0.1), 13.8 ± 2.3 and 13.8 ± 2.2 at 1.8 years (P = 0.99), and 13.6 ± 2.2 and 14.2 ± 2.7 at final follow-up (P = 0.29). The recovery rate of the JOA scores was 56.7 ± 30.0% and 46.7 ± 29.2% at 1.8 years (P = 0.22) and 51.0 ± 32.5 and 57.6 ± 31.1 at the final follow-up (P = 0.42). The subdomains assessed by the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire at follow-up were cervical spine function, 68.7 ± 27.5 in the closure group and 67.7 ± 30.0 in the nonclosure group (P = 0.93); upper extremity function, 78.6 ± 24.3 and 87.6 ± 15.4 (P = 0.40); lower extremity function, 69.9 ± 26.0 and 73.9 ± 22.5 (P = 0.68); bladder function, 74.6 ± 22.6 and 84.9 ± 29.2 (P = 0.18); and quality of life, 53.9 ± 25.3 and 56.2 ± 18.1 (P = 0.96). Conclusion. Lamina closure did not significantly impact the long-term surgical outcomes of laminoplasty for cervical myelopathy. Although not statistically significant, the recovery rate tended to decline in the closure group compared with the nonclosure group during the long-term follow-up period, and the utilization of a laminar retention device to prevent the laminar closure should be considered.

Biomechanical evaluation of the fixation strength of lumbar pedicle screws using cortical bone trajectory: a finite element study.

OBJECT Cortical bone trajectory (CBT) maximizes thread contact with the cortical bone surface and provides increased fixation strength. Even though the superior stability of axial screw fixation has been demonstrated, little is known about the biomechanical stiffness against multidirectional loading or its characteristics within a unit construct. The purpose of the present study was to quantitatively evaluate the anchorage performance of CBT by the finite element (FE) method. METHODS Thirty FE models of L-4 vertebrae from human spines (mean age [± SD] 60.9 ± 18.7 years, 14 men and 16 women) were computationally created and pedicle screws were placed using the traditional trajectory (TT) and CBT. The TT screw was 6.5 mm in diameter and 40 mm in length, and the CBT screw was 5.5 mm in diameter and 35 mm in length. To make a valid comparison, the same shape of screw was inserted into the same pedicle in each subject. First, the fixation strength of a single pedicle screw was compared by axial pullout and multidirectional loading tests. Next, vertebral fixation strength within a construct was examined by simulating the motions of flexion, extension, lateral bending, and axial rotation. RESULTS CBT demonstrated a 26.4% greater mean pullout strength (POS; p = 0.003) than TT, and also showed a mean 27.8% stronger stiffness (p < 0.05) during cephalocaudal loading and 140.2% stronger stiffness (p < 0.001) during mediolateral loading. The CBT construct had superior resistance to flexion and extension loading and inferior resistance to lateral bending and axial rotation. The vertebral fixation strength of the construct was significantly correlated with bone mineral density of the femoral neck and the POS of a single screw. CONCLUSIONS CBT demonstrated superior fixation strength for each individual screw and sufficient stiffness in flexion and extension within a construct. The TT construct was superior to the CBT construct during lateral bending and axial rotation.

Factors affecting the postoperative progression of thoracic kyphosis in surgically treated adult patients with lumbar degenerative scoliosis.

Study Design. A retrospective case series of patients treated surgically for degenerative lumbar scoliosis (DLS). Objective. To determine incidence and risk factors of progressive global thoracic kyphosis (pGTK) after surgery for DLS. Summary of Background Data. Sagittal balance affects the surgical treatment of spinal deformity in adults. Little is known about the loss of sagittal balance due to pGTK, or about the risk factors for pGTK, after surgery for DLS. Methods. We reviewed records from a multicenter database of adults with DLS, treated with posterior spinal fusion. Inclusion required an age of 50 years or more at the time of surgery, an upper instrumented vertebra at T9 and below, more than 5 fused segments, and at least 2 years of follow-up. We included 73 patients with a mean age of 68.3 years (range, 51–77 yr) and a mean follow-up period of 3.6 years (range, 2–11 yr). Independent risk factors for pGTK were identified by logistic regression analysis. Results. Significant pGTK, defined as an increase in thoracic kyphosis of more than 10° from before surgery to the time of final follow-up, was observed in 41% of the patients. Loss of the sagittal vertical axis was larger in patients with pGTK than without (4.7 vs. 1.5 cm; P = 0.02). Risk analysis showed larger lumbar lordosis correction in patients with pGTK. Multivariate logistic regression analysis identified an age greater than 75 (odds ratio, 5.53; P = 0.02, 95% confidence interval [1.4–22.4]) and sacropelvic fusion (odds ratio = 2.66, P = 0.02, 95% confidence interval [1.5–11.1]) as independent risk factors for pGTK. Conclusion. The pGTK incidence after surgery for DLS was 41%. Age, sacropelvic fusion, and a larger sagittal correction were identified as pGTK risk factors. Long-term follow-up will provide more data on the clinical impact of pGTK in elderly patients. Level of Evidence: 3

Surgical treatment of spinal extradural arachnoid cysts in the thoracolumbar spine.

BACKGROUND Because an idiopathic spinal extradural arachnoid cyst (SEAC) is rare, its optimal surgical treatment remains controversial. OBJECTIVE To evaluate the results of surgical treatments for SEACs and to clarify features of the disease associated with poor outcomes. METHODS Twelve patients with SEACs who underwent surgery at our hospital between 1988 and 2008 were examined retrospectively. The mean follow-up period was 4.7 years. Total resection of the cyst was performed in 7 patients and closure of the dural defect without cyst resection in 5 patients. Surgical outcomes were evaluated with regard to the duration of symptoms, the size of the cyst, and the surgical procedure used. RESULTS Neurological recovery was observed in all patients, and there was no recurrence. Poor outcomes were observed in patients with a long duration of symptoms (>1 year, P < .01) and large cyst size (>5 vertebrae, P < .05). The surgical procedure had no significant association with the postoperative neurological recovery. However, there was a significant difference in the degree of the mean postoperative kyphotic angle between the patients treated by total resection of the cyst (9.7 degrees) and those treated by closure of the dural defect without cyst resection through selective laminectomy (2.2 degrees) (P < .01). CONCLUSION There was no significant difference in postoperative neurological recovery between the 2 surgical procedures. However, closure of the dural defect without cyst resection was less invasive, preventing postoperative kyphotic deformity of the thoracolumbar spine.

Incidence and Risk Factors of Adjacent Cranial Facet Joint Violation Following Pedicle Screw Insertion Using Cortical Bone Trajectory Technique.

Study Design. Retrospective study evaluating cranial facet joint violation (FJV) by pedicle screws. Objective. The aim of the study was to determine the incidence and risk factors of FJV following screw placement via cortical bone trajectory (CBT). Summary of Background Data. CBT is a new minimally invasive technique for lumbar pedicle screw insertion that minimizes muscle dissection. Inserting a screw from a more caudal entry point can reduce iatrogenic damage to the cranial facet joint; however, no previous reports exist describing the incidence of FJV secondary to the CBT technique. Methods. We reviewed 202 consecutive patients who underwent lumbar pedicle screw instrumentation using CBT from October 2011 to June 2015. Postoperative CT scans were obtained to determine the degree and incidence of FJV. Clinical and imaging data were analyzed to clarify the risk factors of FJV. The detailed positions of the proximal screws were also investigated and compared between the FJV and non-FJV groups. Results. The incidence of FJV by the proximal screws was 11.8% (48/404), with no occurrence of intra-articular FJV. Multiple logistic regression analysis revealed that age >70 years, vertebral slip >10%, and adjacent facet joint degeneration (Pathrias grade 2 or 3) were independent factors significantly affecting FJV. There were statistically significant differences between the FJV and non-FJV groups in the facet-screw distance (3.2 ± 1.0 vs. 8.1 ± 2.3 mm, P < 0.01), the cranial angle (25.8 ± 6.3° vs. 29.9 ± 7.6°, P < 0.01), and the lamina-screw head distance (5.6 ± 1.6 vs. 6.4 ± 1.9 mm, P < 0.01). Conclusion. Lumbar pedicle screw placement via CBT would reduce FJV; however, special care should be taken in patients with age >70 years, vertebral slip >10%, and facet degeneration. Level of Evidence: 3