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• We aim to investigate the effects of cross-link position on rod stress in lumbar pedicle subtraction osteotomy (PSO) site by using finite element model (FEM). • The geometry and dimensions of FEM were obtained from a high-resolution computed tomography scan data of a 65 years old female patient with spinal sagittal imbalance. • The peak von mises stress (PVMS) of rod at PSO site decreased as the cross-link is located apart from the PSO site during flexion and extension. • Cross-link at two levels apart from the PSO site does not increase the risk of rod fracture. The purpose of this study is to investigate the effect of the cross-link position on the rod fracture phenomenon during pedicle subtraction osteotomy (PSO) surgery using finite element model (FEM). A three-dimensional finite element model of a lumbar spine with sagittal imbalance was constructed using computed tomography data of a 65-year-old female patient. After simulating the standard PSO at the L4 level, we constructed four models, specifically a model without a cross-link and three models with a cross-link at three different sites. The peak von Mises stress (PVMS) of the rod around the PSO site was measured after applying physiological loads (flexion, extension, axial rotation, and lateral bending) in each model. The measured PVMS outcomes at the PSO site were 135.8, 135.9, 208.9, and 384.7 MPa for model 1, 2, 3, and 4 during flexion, and 180.0, 180.1, 210.1, and 445.7 MPa during extension. These results show that when the cross-link is located at the PSO site, the rod stress at the PSO site increases significantly during flexion and extension. As the cross-link moved away from the PSO site, the effect on the rod stress decreased. When the cross-link was placed two levels away from the PSO site, the rod stress was scarcely affected. When the cross-link during PSO surgery was positioned two levels away from the PSO site, the risk of rod fracture did not increase. [ABSTRACT FROM AUTHOR]

• We aim to investigate whether cross-link is a risk factor for rod fracture at the pedicle subtraction osteotomy (PSO) site by using finite element model (FEM). • The geometry and dimensions of FEM were obtained from a high-resolution computed tomography scan data of a 65 years old female patient with spinal sagittal imbalance. • After PSO surgery, PVMS of the rod was significantly increased during flexion and extension at PSO site. • With cross-link at PSO site, PVMS of rod was further significantly increased during flexion and extension. We aim to investigate using finite element model (FEM) whether the use of a cross-link is a risk factor for rod fracture at the pedicle subtraction osteotomy (PSO) site. The geometry and dimensions of the FEM were obtained from a high-resolution computed tomography scan data of a 65 years old female patient with spinal sagittal imbalance. The intact model was modified to place PSO on the L4 spine. A cross-link was placed at the PSO site. A multisegment spinal fusion model from L1 to the pelvis was used to compare and analyze the peak von Mises stress (PVMS) values of the implants. A compressive follower load of 400 N was added to the validated intact lumbar spinal model in the follower load path direction. After PSO surgery, the PVMS of the rod was significantly increased during flexion and extension at the PSO site. With the cross-link at the PSO site, the PVMS of the rod was further significantly increased during flexion and extension. The cross-link at the PSO site increased the risk of rod facture, especially during flexion and extension stress. [ABSTRACT FROM AUTHOR]

We aim to characterize the biomechanical properties of a modified iliac screw fixation method compared with the classic iliac screw fixation and the S2 alar iliac screw (S2AI) fixation using a FEM. A three-dimensional, non-linear FEM of lumbosacral spine and pelvis (L1-pelvis) was modified to simulate 3 different iliac screw fixations based on posterior screw fusion. The peak von Mises stress (PVMS) values of the iliac screws in the 3 different iliac screw fixations were recorded in during flexion/extension/axial rotation/lateral bending. The interaction stress which arose between the screw head and the shaft of iliac screws, was also measured for each case. The PVMS values of the 3 different iliac screw fixation techniques were lower than the fatigue strength levels under physiological loadings. PVMS of iliac screws was observed in the screw shaft for S2AI, in the screw neck for the modified iliac screw technique, and in the offset connectors of the classic iliac screw technique. The interaction between the screw head and the neck was compressed in modified iliac screw fixation technique. On the other hand, distraction force was observed in the S2AI technique between the screw head and the screw shaft. This FEM study supports our previous clinical results, which found that the modified iliac screw fixation technique can be an effective alternative sacropelvic fixation technique comparable to the classic iliac screw and the S2AI technique. [ABSTRACT FROM AUTHOR]

Background Context: There are several reports regarding pathogeneses and risk factors for proximal junctional kyphosis (PJK) in adult spinal deformity surgery. However, the relationship between thoracolumbar muscle condition and PJK has not been investigated yet.Purpose: We aimed to elucidate the thoracolumbar muscle conditions on the incidence of PJK in adult patients with spinal deformity treated by long instrumented spinal fusion surgery stopping at thoracolumbar junction with a minimum 2-year follow-up (F/U).Study Design: This is a retrospective review of prospective database.Patient Sample: A total of 44 cases of patients having multilevel spinal instrumented fusion stopping at thoracolumbar junction for adult spinal deformity in two academic institutions from 2004 to 2012 were enrolled in this study.Outcome Measures: For clinical outcomes, the Scoliosis Research Society questionnaire-22r (SRS-22r) was used preoperatively and at ultimate F/U.Methods: Inclusion criteria were age >20 and minimum five vertebrae fused from T9 upper instrumented vertebra (UIV) to any lower instrumented vertebra. Radiographic assessment included pelvic parameters, Cobb measurements in the coronal-sagittal plane, and measurements of the thoracolumbar muscularity (cross-sectional area of muscle-vertebral body ratio×100) and fatty degeneration (signal intensity of muscle-subcutaneous fat ratio×100).Results: The prevalence of PJK was 38.6%. Age at surgery, gender, fusions extending to the sacrum, levels fused, combined anterior-posterior surgery, and a UIV level were not significantly different between PJK and non-PJK groups. Lower bone mineral density (BMD; T-score: -2.5 vs. -1.3, p=.003) and lower muscularity and higher fatty degeneration at the level of T10 to L2 (131.8 vs. 159.0, p<.01; 59.0 vs. 44.0, p<.001, respectively) were identified risk factors for PJK. Radiographic parameters demonstrated a higher postoperative lumbar lordosis (LL) change (43.8 vs. 29.3, p<.001) and a larger sagittal vertical axis (SVA) change with surgery (8.4 cm vs. 4.8 cm, p=.01) in those with PJK. Although SRS postop pain scores were inferior in PJK group (3.3 vs. 4.1, p<.05), there were no significant differences in the average scores between the groups (3.5 vs. 3.3, p<.05).Conclusions: Patients with PJK had lower thoracolumbar muscularity and higher fatty degeneration than patients without PJK before surgery. Our data suggest that osteoporosis, large corrections in LL and SVA with surgery, and lower muscularity and higher fatty degeneration at the thoracolumbar area can lead to PJK. [ABSTRACT FROM AUTHOR]

Purpose of study: to evaluate pulmonary function changes 5 years or more prospectively after surgery in patients with adolescent idiopathic scoliosis (AIS) relative to the type of surgical approach used for the spinal arthrodesis (Table 1) Table 1 Postoperative changes in PFTs Group Preoperative FVC/FEV1 3-month PO 1-year PO 2-year PO 5-year PO G1 PSF-IC (n=43) 2.80/2.39 2.86/2.43 2.94/2.46 3.13/2.70 3.26/2.76 G2 PSF-TP (n=39) 2.92/2.39 2.47/2.10 2.74/2.30 3.04/2.56 3.04/2.52 G3 ASF-TC (n=15) 3.09/2.69 2.44/2.39 2.71/2.47 2.96/2.56 2.83/2.42 G4 ASF/PSF (n=12) 2.38/2.00 2.11/1.65 2.33/1.96 2.44/2.09 2.54/2.15 G2 + 3 + 4 (n=66) 2.85/2.41 2.39/2.10 2.64/2.27 2.91/2.47 2.91/2.43 PO = post-op. . Methods used: A total of 109 patients with AIS undergoing surgical treatment were prospectively evaluated with pulmonary function tests (PFTs), forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV 1 ) before surgery, 3 months, 1 year, 2 years and a minimum 5 years after surgery (5 to 14 years). All patients were divided into four groups. Group 1 (n=43) posterior spinal fusion with iliac crest bone graft (PSF-IC); Group 2 (n=39) PSF with thoracoplasty (PSF-TP); Group 3 (n=15) anterior fusion (ASF) with a rib resection thoracotomy (ASF-TC) and Group 4 (n=12) combined ASF and PSF with autogenous rib and iliac crest graft (ASF/PSF). of findings: Irrespective of the surgical approach used for the spinal arthrodesis, postoperative PFTs (absolute values) improved continuously until 2 years after surgery, then did not change between 2- and 5-year follow-up, except Group 1 (PSF-IC), which continued to improve up to 5 years after surgery. Five years after surgery, Group 1 had statistically increased PFTs both in absolute value and percent predicted, whereas patients in Groups 2, 3 and 4 had unchanged (Groups 2 and 4) or significantly decreased (Group 3) pulmonary function values (p<.05). Relationship between findings and existing knowledge: Irrespective of the surgical approach used, postoperative pulmonary function tests (absolute values) increase until 5 years after surgery. Patients who had no chest cage disruption (Group 1) had a significantly greater improvement in their pulmonary function values at 5 years after surgery than patients with chest cage disruption (Groups 2, 3 and 4). Overall significance of findings: We can choose more appropriate approaches for surgical candidates and predict the change of the pulmonary functions 5 years after operation. Disclosures: No disclosures. Conflict of interest: No conflicts. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we have assessed the effects of muscarinic receptor activation on neural activity in the telencephalon of the zebrafish. Electrically evoked field potentials via the stimulation of the posterior dorsal telencephalon were recorded in the anterior dorsal telencephalon of the ipsilateral hemisphere, with a peak latency of 20–30ms. The application of carbachol (1–25μM) and oxotremorine-M (0.25–60μM) suppressed the amplitude of field potentials in a dose-dependent manner. This suppressive effect was blocked by a muscarinic receptor antagonist, atropine (20μM), and an M1 receptor antagonist, pirenzepine (5μM), but not by the M2 receptor antagonists, methoctramine (5μM) and gallamine (5μM). Oxotremorine-M (1μM) also suppressed the induction of field potentials via the stimulation of the contralateral telencephalon and the medial fiber bundle, which was blocked by atropine (20μM). An acetylcholine esterase inhibitor, physostigmine (20–30μM), reduced the peak amplitude of the evoked field potentials, while increasing late bursting activity. Furthermore, a high dose of physostigmine (100μM) induced spontaneous bursting activity. These results demonstrated the cholinergic influence on the neural activity in the telencephalon of the zebrafish. [Copyright &y& Elsevier]

Background Spinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear. Methods A finite element model of the thoracolumbar spine was used. Nine fusion models with pedicle screw systems implanted at the L2–L3, L3–L4, L4–L5, L5–S1, L2–L4, L3–L5, L4–S1, L2–L5, and L3–S1 levels were developed based on the respective surgical protocols. The developed models simulated flexion–extension using hybrid testing protocol. Findings When spinal fusion was performed at more distal levels, particularly at the L5–S1 level, the following biomechanical properties increased during flexion–extension: range of motion, stress on the annulus fibrosus fibers and vertebra at the adjacent motion segment, and the magnitude of axial forces on the pedicle screw at the uppermost instrumented vertebra. Interpretations The results of this study demonstrate that more distal fusion levels, particularly in spinal fusion including the L5–S1 level, lead to greater increases in the risk of proximal junctional kyphosis and failure, as evidenced by larger ranges of motion, higher stresses on fibers of the annulus fibrosus and vertebra at the adjacent segment, and higher axial forces on the screw at the uppermost instrumented vertebra in flexion–extension. Therefore, fusion levels should be carefully selected to avoid proximal junctional kyphosis and failure. [ABSTRACT FROM AUTHOR]

Background: There have been no standardized surgical options for severe scoliotic curvatures ≥100°. Halo-gravity traction is a viable option for surgical treatment of severe scoliosis. The aim of this study was to evaluate the efficacy and safety of perioperative halo-gravity traction for scoliosis curves ≥100° with respect to radiographic outcomes and clinical complications. Methods: A total of 21 scoliosis patients with ≥100° curves (average 118.7°; range 100°-158°) with a minimum 2-year follow-up (average 41.8 months; range 24.0-97.0 months) who underwent spinal instrumented fusion using perioperative halo-gravity traction were analyzed. Diagnoses were neuromuscular scoliosis (n = 10), idiopathic (n = 9), and congenital (n = 2). In all, 15 patients were treated by the anterior release procedure followed by final posterior fusion and 6 patients by posterior fusion alone. Six patients had only preoperative traction preceding posterior fusion alone, 6 patients only staged traction between anterior release and final posterior fusion, and 9 patients had both preoperative traction preceding anterior release and staged traction preceding final posterior fusion. The average overall traction period in all patients was 67 days (range 10-78 days). Results: Radiographic outcomes demonstrated 51.3% correction of the major Cobb angle, 40 mm correction of apical vertebral translation, 76 mm increase of T1-S1 length, and 20.7% increase of space available for lungs at the ultimate follow-up (all comparisons P < 0.05). Preoperative traction demonstrated 27.5% correction of the major curve Cobb angle, 51.5 mm increase of T1-S1 length, 14.9% increase of space available for the lungs (all comparisons P < 0.05). Staged traction after anterior release demonstrated 37.2% correction of the major curve Cobb angle, 26.1 mm correction of apical vertebral translation, 56.5 mm increase of T1-S1 length, 14.2% increase of space available for the lungs (all comparisons P < 0.05). There were only two patients with a pin-site problem, and one required débridement. There were no neurological deficits or clinical complications. Conclusions: Scoliosis patients with ≥100° curves can be managed successfully by corrective fusion surgery concomitant with perioperative halo-gravity traction without significant complications. [ABSTRACT FROM AUTHOR]

Objective To determine a neurosurgeon's learning curve of surgical treatment for adolescent idiopathic scoliosis (AIS) patients. Methods This study is a retrospective analysis. Forty-six patients were treated by a single neurosurgeon between 2011 and 2017 using posterior segmental instrumentation and fusion. According to the time period, the former and latter 23 patients were divided into group 1 and group 2, respectively. Patients' demographic data, curve magnitude, number of levels treated, amount of correction achieved, radiographic/clinical outcomes, and complications were compared between the groups. Results The majority were females (34 vs. 12) with average ages of 15.0 versus 15.6, respectively. The mean follow-up period was 24.6 months. The average number of fusion levels was similar with 10.3 and 11.5 vertebral bodies in groups 1 and 2, respectively. The average Cobb angle of major curvature was 59.8° and 58.5° in groups 1 and 2, respectively. There observed significant reductions of operative time (324.4 vs. 224.7 minutes, P = 0.007) and estimated blood loss (648.3 vs. 438.0 mL, P = 0.027) in group 2. The correction rate of the major structural curve was greater in group 2 (70.7% vs. 81.0%, P = 0.001). There was no case of neurologic deficit, infection, and revision for screw malposition. One patient of group 1 underwent fusion extension surgery for shoulder asymmetry. Conclusion Radiographic and clinical outcomes of AIS patients treated by a neurosurgeon were acceptable. AIS surgery may be performed with an acceptable rate of complications after about 20 surgeries. With acquisition of surgical experiences, neurosurgeons could perform deformity surgery for AIS effectively and safely. [ABSTRACT FROM AUTHOR]