Automated segmentation of MRI white matter hyperintensities in 8,421 patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: To date, only a few small studies have attempted deep learning-based automatic segmentation of white matter hyperintensity (WMH) lesions in patients with cerebral infarction, which is complicated because stroke-related lesions can obscure WMH borders. We developed and validated deep learning algorithms to segment WMH lesions accurately in patients with cerebral infarction, using multisite datasets involving 8,421 patients with acute ischemic stroke. MATERIALS AND METHODS: We included 8,421 stroke patients from 9 centers in Korea. 2D UNet and SE-Unet models were trained using 2,408 FLAIR MRI from 3 hospitals and validated using 6,013 FLAIR MRIs from 6 hospitals. WMH segmentation performance was assessed by calculating DSC, correlation coefficient, and concordance correlation coefficient compared to a human-segmented gold standard. In addition, we obtained an uncertainty index that represents overall ambiguity in the voxel classification for WMH segmentation in each patient based on the Kullback-Leibler divergence. RESULTS: In the training dataset, the mean age was 67.4±13.0 years and 60.4% were men. The mean (95% CI) DSCs for Unet in internal testing and external validation were respectively 0.659 (0.649-0.669) and 0.710 (0.707-0.714), which were slightly lower than the reliability between humans (DSC=0.744; 95% CI=0.738-0.751; P=.031). Compared with the Unet, the SE-Unet demonstrated better performance, achieving a mean DSC of 0.675 (0.666-0.685; P<.001) in the internal testing and 0.722 (0.719-0.726; P<.001) in the external validation; moreover, it achieved high DSC values (ranging from 0.672 to 0.744) across multiple validation datasets. We observed a significant correlation between WMH volumes that were segmented automatically and manually for the Unet (r=0.917, P<.0001) and even stronger for the SE-Unet (r=0.933, P<.0001). The SE-Unet also attained a high concordance correlation coefficient (ranging from 0.841 to 0.956) in external test datasets. In addition, the uncertainty indices in the majority of patients (86%) in the external datasets were below 0.35, with an average DSC of 0.744 in these patients. CONCLUSIONS: We developed and validated deep learning algorithms to segment WMH in patients with acute cerebral infarction using the largest-ever MRI datasets. In addition, we showed that the uncertainty index can be used to identify cases where automatic WMH segmentation is less accurate and requires human review. ABBREVIATIONS: WMH = white matter hyperintensity; CNN = convolutional neural networks; SE = squeeze-and-excitation; KL = Kullback-Leibler; ReLU = rectified linear unit; LKW = last known well; mRS = modified Rankin Scale; NIHSS = National Institute of Health Stroke Scale; LAA = large artery atherosclerosis; SVO = small vessel occlusion; CE = cardioembolism.

Comparison of two automated CT perfusion software packages in patients with ischemic stroke presenting within 24 h of onset.

Background: We compared the ischemic core and hypoperfused tissue volumes estimated by RAPID and JLK-CTP, a newly developed automated computed tomography perfusion (CTP) analysis package. We also assessed agreement between ischemic core volumes by two software packages against early follow-up infarct volumes on diffusion-weighted images (DWI). Methods: This retrospective study analyzed 327 patients admitted to a single stroke center in Korea from January 2021 to May 2023, who underwent CTP scans within 24 h of onset. The concordance correlation coefficient (ρ) and Bland-Altman plots were utilized to compare the volumes of ischemic core and hypoperfused tissue volumes between the software packages. Agreement with early (within 3 h from CTP) follow-up infarct volumes on diffusion-weighted imaging (n = 217) was also evaluated. Results: The mean age was 70.7 ± 13.0 and 137 (41.9%) were female. Ischemic core volumes by JLK-CTP and RAPID at the threshold of relative cerebral blood flow (rCBF) < 30% showed excellent agreement (ρ = 0.958 [95% CI, 0.949 to 0.966]). Excellent agreement was also observed for time to a maximum of the residue function (T max) > 6 s between JLK-CTP and RAPID (ρ = 0.835 [95% CI, 0.806 to 0.863]). Although early follow-up infarct volume showed substantial agreement in both packages (JLK-CTP, ρ = 0.751 and RAPID, ρ = 0.632), ischemic core volumes at the threshold of rCBF <30% tended to overestimate ischemic core volumes. Conclusion: JLK-CTP and RAPID demonstrated remarkable concordance in estimating the volumes of the ischemic core and hypoperfused area based on CTP within 24 h from onset.

Effect of Blended Perfluorinated Sulfonic Acid Ionomer Binder on the Performance of Catalyst Layers in Polymer Electrolyte Membrane Fuel Cells.

In this study, blended perfluorinated sulfonic acid (PFSA) ionomers with equivalent weights (EWs, g/mol) of ~1000, 980, and 830 are prepared. Catalyst layers (CLs), using blended PFSA ionomers, with different side chain lengths and EWs are investigated and compared to CLs using single ionomers. The ion exchange capacity results confirm that blended ionomers have the target EWs. As a result, blended ionomers exhibit higher ion conductivity than single ionomers at all temperatures due to the higher water uptake of the blended ionomers. This implies that blended ionomers have a bulk structure to form a competent free volume compared to single ionomers. Blended ionomers with short side chains and low EWs can help reduce the activation energy in proton conduction due to enhanced hydrophobic and hydrophilic segregation. In addition, when using the blended ionomer, the CLs form a more porous microstructure to help reduce the resistance of oxygen transport and contributes to lower mass transfer loss. This effect is proven in fuel cell operations at not a lower temperature (70 °C) and full humidification (100%) but at an elevated temperature (80 °C) and lower relative humidity (50 and 75%). Blended ionomer-based CLs with a higher water uptake and porous CL structure result in improved fuel cell performance with better mass transport than single ionomer-based CLs.

Improving performance robustness of subject-based brain segmentation software.

Purpose: Artificial intelligence (AI)-based image analysis tools to quantify the brain have become commercialized. However, insufficient data for learning and scanner specificity is a limitation for achieving high quality. In the present study, the performance of personalized brain segmentation software when applied to multicenter data using an AI model trained on data from a single institution was improved. Methods: Preindicators of brain white matter (WM) information from the training dataset were utilized for preprocessing. During learning, data of cognitively normal (CN) individuals from a single center were utilized, and data of CN individuals and Alzheimer disease (AD) patients enrolled in multiple centers were considered the test set. Results: The preprocessing based on the preindicator (dice similarity coefficient [DSC], 0.8567) resulted in a better performance than without (DSC, 0.7921). The standard deviation (SD) of the WM region intensity (DSC, 0.8303) had a more substantial influence on the performance than the average intensity (DSC, 0.6591). When the SD of the test data WM intensity was smaller than the learning data, the performance improved (0.03 increase in lower SD, 0.05 decrease in higher SD). Furthermore, preindicator-based pretreatment increased the correlation of mean cortical thickness of the entire gray matter between Atroscan and FreeSurfer, and data augmentation without preprocessing did not.Both preindicator processing and data augmentation improved the correlation coefficient from 0.7584 to 0.8165. Conclusion: Data augmentation and preindicator-based preprocessing of training data can improve the performance of AI-based brain segmentation software, both increasing the generalizability and stability of brain segmentation software.

Grain Boundary-Rich Copper Nanocatalysts Generated from Metal-Organic Framework Nanoparticles for CO2 -to-C2+ Electroconversion.

Due to severe contemporary energy issues, generating C2+ products from electrochemical carbon dioxide reduction reactions (eCO2 RRs) gains much interest. It is known that the catalyst morphology and active surface structures are critical for product distributions and current densities. Herein, a synthetic protocol of nanoparticle morphology on copper metal-organic frameworks (n-Cu MOFs) is developed by adjusting growth kinetics with termination ligands. Nanoscale copper oxide aggregates composed of small particulates are yielded via calcining the Cu-MOF nanoparticles at a specific temperature. The resulting nanosized MOF-derived catalyst (n-MDC) exhibits Faradaic efficiencies toward ethylene and C2+ products of 63% and 81% at -1.01 V versus reversible hydrogen electrode (RHE) in neutral electrolytes. The catalyst also shows prolonged stability for up to 10 h. A partial current density toward C2+ products is significantly boosted to -255 mA cm-2 in an alkaline flow cell system. Comprehensive analyses reveal that the nanoparticle morphology of pristine Cu MOFs induces homogeneous decomposition of organic frameworks at a lower calcination temperature. It leads to evolving grain boundaries in a high density and preventing severe agglomeration of copper domains, the primary factors for improving eCO2 RR activity toward C2+ production.

Safety and Efficacy of Intraoperative Doppler Sonography-Assisted Cervical Pedicle Screw Fixation-A Retrospective Comparison with Conventional Pedicle Screw Implantation.

STUDY DESIGN: A Retrospective Cohort Study. OBJECTIVE: To introduce a new Doppler sonography-assisted pedicle screw fixation technique that enables vertebral artery (VA) monitoring during surgery and compares the accuracies of Doppler sonography-assisted cervical pedicle screw fixation and the conventional technique. METHODS: This retrospective study was performed on 164 consecutive patients that underwent pedicle-based screw fixation from C2 to C6 between January 2013 and August 2020. Surgery was performed without intraoperative Doppler sonography in 84 cases (the Control group) or with intraoperative Doppler sonography in 80 cases (the Doppler group). Proper positioning of pedicle screws was graded, and the incidences of VA injury and screw breach in the Control and Doppler groups were compared. RESULTS: Three hundred and ninety-nine screws were placed in the 164 patients (Doppler, 186 screws; Control, 213 screws). The percentages of well-positioned screws in the two groups were significantly different (Doppler, 97.8%; Control, 85.0%). There were two cases of VA injury in the Control group, an incidence of 2.4%, but no case in the Doppler group. CONCLUSION: Doppler sonography can be used intraoperatively to help guide the trajectory of the cervical pedicle screw insertion. It can detect the VA inside the screw trajectory and may reduce the risk of VA injury during cervical pedicle screw fixation.

Are plain radiographic measurements still consistent with a diagnosis of basilar invagination in the era of cross-sectional images?

Retrospective cross-sectional study To evaluate the validity and obtain optimal cutoff values of 3 radiologic measurements for the diagnosis of basilar invagination (BI). Two hundred seventy-six patients (46 patients who underwent atlantoaxial fusion for BI and 230 patients who were treated for minor cervical trauma) seen in a single institution from January 2010 to December 2016 were included in this study. Age, sex, and body mass index were adjusted for the patients. The Ranawat index (RI), modified Ranawat method (MRM), and Redlund-Johnell method (RJM) were used to diagnose BI on plain radiographs. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and diagnostic odds ratio of 3 radiologic measurements were compared. We also calculated the optimized cutoff values of 3 radiologic measurements using the receiver operating characteristic curve in our patients. The mean age of the 130 women and 146 men was 58.3 ±â€…14.5 years. The mean values of RI, MRM, and RJM in the BI group were 12.5 ±â€…3.3, 23.1 ±â€…3.8, and 27.3 ±â€…3.6 in women and 13.6 ±â€…2.6, 26.8 ±â€…4.2, and 34.7 ±â€…5.1 in men. There was a significant difference between the sexes (P < .05). The accuracies of RI, MRM, and RJM were 95%, 89.6%, and 92.3% in women and 93%, 68.2%, and 85.4% in men, respectively. The optimized cutoff values of RI, MRM, and RJM were 14, 26, and 32 mm in women and 15, 29, and 38 mm in men. Three radiologic measurements (RI, MRM, and RJM) are reliable for the diagnosis of BI even in the era of cross-sectional images. The validity of these measurements depends on sex and particular radiologic measurement. The optimized cutoff values of RI, MRM, and RJM were 14, 26, and 32 mm in women and 15, 29, and 37 mm in men. These cutoff values showed high validity when compared to the CT and MRI findings.

Analysis of Associating Radiologic Parameters With Clinical Outcomes After Posterior C1-2 Fusion.

OBJECTIVE: To evaluate which radiologic parameters affect clinical outcomes in patients underwent posterior C1-2 fusion for atlantoaxial dislocation. METHODS: From January 2014 to December 2017, among 98 patients underwent C1-2 posterior fusion, patients with previous cervical surgery or extending to subaxial spine or basilar invagination were excluded. Finally, 38 patients were included. O-C2, C1-2, C1-C7, C2-C7 cobb angle (CA), T1 slope, C1-7, C2-7 sagittal vertical axis (SVA), and posterior atlantodental interval (PADI) were measured at preoperative and postoperative 1 year. The difference between postoperative and preoperative values for each parameter was designated as Δvalue. Postoperative subaxial kyphosis (PSK) was defined to decrease ≥ 10° at subaxial spine. Visual analogue scale (VAS), Japanese Orthopedic Association (JOA) score, Neck Disability Index (NDI) were used to evaluate clinical outcomes. RESULTS: Mean age was 54.4 ± 15.9. Male to female was 14 to 24. Of radiologic parameters, C1-7 SVA and PADI were significantly changed from 26.4 ± 12.9 mm, 17.1 ± 3.3 mm to 22.6 ± 13.0 mm, 21.6 ± 3.4 mm. ΔC1-2 CA was correlated with ΔC1-7 CA and ΔC2-7 SVA. ΔPADI correlates with ΔO-C2 CA. VAS correlates with ΔC1-7 CA (p = 0.03). JOA score also correlates with ΔC2-7 SVA (p = 0.02). NDI was associated with ΔPADI (p < 0.01). The incidence of PSK was 23.7%, and not significant with clinical outcomes. CONCLUSION: ΔC1-2 CA was correlated with ΔC1C7 CA, ΔC2-7 SVA. ΔC1-7 CA, ΔC2-7 SVA, and ΔPADI were the key radiologic parameters to influence clinical outcomes. Postoperative C1-2 angle should be carefully determined as a factor affecting clinical outcomes and cervical sagittal alignment.

Bimetallic Gold-Silver Nanostructures Drive Low Overpotentials for Electrochemical Carbon Dioxide Reduction.

Alloy formation is an advanced approach to improve desired properties that the monoelements cannot achieve. Alloys are usually designed to tailor intrinsic natures or induce synergistic effects by combining materials with distinct properties. Indeed, unprecedented properties have emerged in many cases, superior to a simple sum of pure elements. Here, we present Au-Ag alloy nanostructures with prominent catalytic properties in an electrochemical carbon dioxide reduction reaction (eCO2RR). The Au-Ag hollow nanocubes are prepared by galvanic replacement of Au on Ag nanocubes. When the Au-to-Ag ratio is 1:1 (Au1Ag1), the alloy hollow nanocubes exhibit maximum Faradaic efficiencies of CO production in a wide potential range and high mass activity and CO current density superior to those of the bare metals. In particular, overpotentials are estimated to be similar to or lower than that of the Au catalyst under various standard metrics. Density functional theory calculations, machine learning, and a statistical consideration demonstrate that the optimal configuration of the *COOH intermediate is a bidentate coordination structure where C binds to Au and O binds to Ag. This active Au-Ag neighboring configuration has a maximum population and enhanced intrinsic catalytic activity on the Au1Ag1 surface among other Au-to-Ag compositions, in good agreement with the experimental results. Further application of Au1Ag1 to a membrane electrode assembly cell at neutral conditions shows enhanced CO Faradaic efficiency and current densities compared to Au or Ag nanocubes, indicating the possible extension of Au-Ag alloys to larger electrochemical systems. These results give a new insight into the synergistic roles of Au and Ag in the eCO2RR and offer a fresh direction toward a rational design of bimetallic catalysts at a practical scale.

A new nomenclature system for the surgical treatment of cervical spine deformity, developing, and validation of SOF system.

PURPOSE: To develop and assess the reliability of new nomenclature system that systematically organizes osteotomy techniques and briefly describes the surgical approach, the surgical sequence, and the fixation technique for cervical spine deformity (CSD). METHODS: We developed a new classification system (SOF system) for CSD surgery that describes the sequence of surgical approach (S), the grade of osteotomy (O), and the information of fixation (F) using alphanumeric codes. Twenty CSD osteotomies (8 anterior osteotomies, 12 posterior osteotomies) were included in this study to evaluate the inter- and intra-observer agreement based on operation records. Six observers performed independent evaluations of the operation records in random order. Each observer described 20 CSD surgeries using the SOF system twice (> 30 days between assessments) based on operation records to validate SOF system. RESULTS: Overall agreement (among all six observers at the initial assessment) on the anterior and posterior osteotomy was ICC = 0.96 and ICC = 0.91, respectively. Overall agreement (repeat observations after at least 30 days) on the anterior and posterior osteotomy was ICC = 0.96 and ICC = 0.91, respectively. This data showed that both inter- and intra-observer agreement revealed 'excellent'. CONCLUSION: This study introduces the SOF system of the CSD surgery to understand the surgical sequence, the type of osteotomy and the fixation techniques. The investigation of the inter- and intra-observer agreement revealed 'excellent agreement' for both anterior and posterior osteotomies. Thus, SOF system can provide a consistent description of the various CSD surgeries and its use will provide a common frame for CSD surgery and help communicate between surgeons.

Analysis of postoperative dysphagia after anterior cervical decompression and fusion.

Purpose: To investigate the incidence and risk factors of postoperative dysphagia after anterior cervical decompression and fusion (ACDF) in terms of demographic, procedural and anaesthetic perspectives.Materials and methods: Medical records and radiologic data of patients who underwent anterior cervical surgery performed by two surgeons in a single centre between January 2012 and December 2015 were retrospectively analysed. Patients with spinal tumours, infective spondylitis and traumatic cervical pathologies were excluded. Patients with preoperative dysphagia and previous history of anterior cervical surgery were also excluded. Finally, 127 patients were enrolled. Bazaz dysphagia score was used for the diagnosis of postoperative dysphagia.Results: The incidence of postoperative dysphagia was 10.2% at six weeks after ACDF. Nine patients showed mild dysphagia that fully recovered at three months after ACDF. Four patients showed moderate dysphagia that also recovered fully at six months after surgery. The incidence of postoperative dysphagia increased significantly in cases of C4 or C5 level involvements. Age, sex, hypertension, body mass index, postoperative soft tissue swelling, intubation difficulty and intubation tools were not significant risk factors of ACDF. Diabetes mellitus, two surgical levels, the use of plate, long anaesthetic and operative time and large intubation tube size were causative factors of postoperative dysphagia in multivariable analysis (p < 0.05).Conclusions: The incidence of postoperative dysphagia after ACDF was relatively low, and the prognosis was good.

Transdiscal C7 Pedicle Subtraction Osteotomy With a Strut Graft and the Correction of Sagittal and Coronal Imbalance of the Cervical Spine.

BACKGROUND: Cervical spine deformity negatively affects patients' quality of life. Pedicle subtraction osteotomy (PSO) has reported to correct cervical deformity but it is challenging and carries a significant risk of morbidity. OBJECTIVE: To report transdiscal C7 PSO with a strut graft for the correction of sagittal and coronal imbalance in patients with fixed cervical deformity. METHODS: After standard exposure, the spine was instrumented from C2 to T3. T1 subtotal laminectomy, and C6 to C7 total laminectomies were necessary for C7 PSO. Osteotomy was initiated with removal of C6-7 and C7-T1 facet joints to isolate C7 pedicles and identify bilateral C7/C8 roots. Bilateral C7 pediculectomies and transdiscal PSO were performed. A rectangular strut allograft was then inserted into the PSO site. The location of the strut graft was used as a fulcrum of sagittal and coronal correction. The head fixator was released and the head was extended under intraoperative neuromonitoring, and then detailed sagittal and coronal balances were controlled by compressing or distracting between the pedicle screws above and below the osteotomy. RESULTS: This technique was applied in 2 patients with fixed subaxial cervical deformities. Transdiscal PSO could add more amount of correction and provide the additional fusion surface. The strut graft prevented sagittal translation, foraminal narrowing, and excessive focal cord kinking during PSO. Both patients showed radiologic and clinical improvements after surgery, and no neurovascular complication occurred after the surgery. CONCLUSION: Transdiscal C7 PSO with a strut graft placement provided a safe way of correcting sagittal and coronal imbalance simultaneously and reduced neurological complication by preventing sagittal translation, foraminal narrowing and spinal cord kinking.

Control of solutal Marangoni-driven vortical flows and enhancement of mixing efficiency.

HYPOTHESIS: In droplet microfluidics applications, flow control and mixing in a small volume without any active external devices is a challenge. Vapor-mediated solutal Marangoni flows can be effectively generated by applying the vapor of a volatile liquid, which can be possibly controlled, and can eventually be used in a mixing enhancement device. EXPERIMENTS: We investigated and controlled vapor-mediated solutal Marangoni flows by varying the local surface tension. We systematically tested the effects of different volatile liquids and their vapor concentration on the flow pattern. Furthermore, by varying the number of vapor sources, we generated and controlled multiple vortices, and analyzed them by particle image velocimetry (PIV). The proposed method was applied to a mixing enhancement application. FINDINGS: We show that in addition to the surface tension of the volatile liquid, the vapor concentration also influenced the local surface tension along the interface, which in turn changed the internal flow velocity. To predict the flow velocity and oscillatory frequency of the solutal Marangoni flow, we developed a theoretical model based on scaling analysis that showed a good agreement with the experimental results. We believe that the current study will motivate low-cost and portable sample flow control and mixing systems in the near future.

Accuracy evaluation of placements of three different alternative C2 screws using the freehand technique in patients with high riding vertebral artery.

An observational study.To evaluate the safeties of placing three different alternative C2 screws using the freehand technique under high riding vertebral artery (HRVA) and to analyze the C2 morphometry in patients with HRVA.A retrospective analysis of radiologic data was performed on patients that underwent C2 instrumentation from September 2004 to December 2017. Two hundred fifty-one patients were included, and 90 of these patients (35.9%) had a unilateral or bilateral HRVA. We placed three alternative C2 screws including superior pars, inferior pars, and translaminar screws. Computed tomography was used to assess cortical breeches of screw placement and obtain morphometric measurements of C2 pars and lamina, that is, superior pars height/length, inferior pars length, and laminar thickness/length. We used the modification of the all India Institute of Medical Sciences outcome to define cortical breach.In total, 117 alternative C2 screws were inserted in 90 patients; 7 superior pars screws (6%), 69 inferior pars screws (59.0%), and 41 translaminar (35%) screws. Although cortical breaches occurred during 31 screw placements (26.5%), these were unacceptable in only two cases (1.7%). No symptomatic neurovascular complication was observed after screw placement in any case. Mean height of C2 superior pars was 3.8 ±â€Š1.8 mm and mean thickness of C2 lamina was 5.2 ±â€Š1.1 mm. Mean lengths of superior pars, inferior pars, and lamina were 17.8 ±â€Š3.0 mm, 13.6 ±â€Š2.2 mm, and 26.7 ±â€Š3.3 mm, respectively. Superior pars height and lamina thickness < 3.5 mm that was a minimal diameter of cervical screw were 49.6% and 6.8%, alternative C2 screw was not available in these cases.Placements of alternative C2 screws using the freehand technique were achieved accurately and safely in patients with HRVA. However, preoperative morphometric evaluation is essential to determine the best option for C2 instrumentation and C2 screw length to avoid neurovascular complications.

Clinical Analysis of Radiologic Measurements in Patients with Basilar Invagination.

OBJECTIVE: To investigate correlations between radiologic measurements and clinical outcomes in patients with basilar invagination (BI). METHODS: The medical records and radiologic data of 46 patients (27 women) who had undergone posterior atlantoaxial fusion or occipitocervical fusion for BI from January 2010 to June 2018 were retrospectively analyzed. Patients under 15 years old or with a polytraumatic, tumorous, or infectious pathology were excluded. The modified Ranawat method (MRM) and the Redlund-Johnell method (RJM) were used to obtain radiographic measurements of basilar invagination preoperatively, subacute postoperatively, and at 3-month and last follow-up. Visual analogue scale, Neck Disability Index, and Japanese Orthopedic Association (JOA) scores were also assessed. Correlations between MRM and RJM measurements and clinical outcomes were evaluated. RESULTS: Mean age of patients was 59.9 ± 16.5 years, mean body mass index was 23.5 ± 4.6 kg/m2, and mean follow-up was 37.9 ± 23.8 months. Postoperative radiologic measurements increased about 36% of preoperative radiologic measurements. Subsidence at the C1-2 joint occurred in most patients at 3 months postoperatively, but clinical outcomes did not deteriorate. JOA scores were linearly correlated with percentage increases in both radiologic measurements subacute postoperatively (P < 0.05), but this significance was not maintained until the last follow-up. Occipital numbness and neuralgia were most common postoperative complications. One case of neurovascular injury and 3 cases of postoperative dysphagia occurred postoperatively. CONCLUSIONS: The subacute postoperative neurological outcomes of BI patients are significantly related to the amount of vertical reduction.

Analysis of Risk Factors for Posterior C1 Screw-Related Complication: A Retrospective Study of 358 Posterior C1 Screws.

BACKGROUND: Although C1 screw fixation is becoming popular, only a few studies have discussed about the risk factors and the patterns of C1 screw complications. OBJECTIVE: To investigate the incidence of C1 screw complications and analyze the risk factors of the C1 screw complications. METHODS: A total of 358 C1 screws in 180 consecutive patients were analyzed for C1 screw complications. Screw malposition, occipital neuralgia, major complications, and total C1 screw complications were analyzed. RESULTS: The distribution of C1 screw entry point is as follows: inferior lateral mass, 317 screws (88.5 %); posterior arch (PA), 38 screws (10.7 %); and superior lateral mass, 3 screws (0.8 %). We sacrificed the C2 root for 127 screws (35.5 %). C1 instrumentation induced 3.1 % screw malposition, 6.4 % occipital neuralgia, 0.6 % vascular injury, and 3.4 % major complications. In multivariate analysis, deformity (odds ratio [OR]: 2.10, P = .003), traumatic pathology (OR: 4.97, P = .001), and PA entry point (OR: 3.38, P = .001) are independent factors of C1 screw malposition. C2 root resection can decrease the incidence of C1 screw malposition (OR: 0.38, P = .012), but it is a risk factor of occipital neuralgia (OR: 2.62, P = .034). Advanced surgical experience (OR: 0.09, P = .020) correlated with less major complication. CONCLUSION: The incidence of C1 screw complications might not be uncommon, and deformity or traumatic pathology and PA entry point could be the risk factors to total C1 screw complications. The PA screw induces more malposition, but less occipital neuralgia. C2 root resection can reduce screw malposition, but increases occipital neuralgia.

Difference of Dynamic Morphometric Changes Between in Patients with Ossification of Posterior Longitudinal Ligament and Patients with Cervical Spondylosis: Assessment by Cervical Dynamic Magnetic Resonance Imaging.

PURPOSE: To evaluate differences between thicknesses of the ligamentum flavum (LF) and diameter of the spinal canal in different neck positions in patients with ossification of the posterior longitudinal ligament (OPLL) and patients with cervical degenerative spondylosis (CDS) using cervical dynamic magnetic resonance imaging (MRI). METHODS: Eighty-eight patients (66 CDS and 22 OPLL) who underwent neutral and dynamic MRI at our institute from February 2014 to July 2017 were the subjects of this retrospective study. Canal diameters and LF thicknesses were measured and Muhle's grades were determined in neutral and dynamic MRI from C2-C3 to C7-T1. Patients with CDS and OPLL were compared with respect to changes in morphometric parameters. Statistical analysis was performed using SPSS software and statistical significance was accepted for P values < 0.05. RESULTS: Mean ages in the CDS and OPLL groups were 68.2 ± 12.27 and 63.1 ± 9.36 years, respectively. Mean canal diameters were smaller in extension than in neutral at all measured levels, especially between C3-C4 and C6-C7 in patients with CDS. LF thickness in extension was significantly greater than in neutral and flexion positions in the CDS group, but not in the OPLL group. In addition, positional changes in Muhle's grades in the CDS group were significantly greater than in the OPLL group (P = 0.042). CONCLUSIONS: Dynamic morphometric changes were found to be significantly greater in the CDS group than in the OPLL group. The study shows dynamic MRI may provide additional information in CDS patients.

Validity of a Smartphone Application (Sagittalmeter Pro) for the Measurement of Sagittal Balance Parameters.

OBJECTIVE: The study was aimed to compare the validity, reproducibility, precision, and efficiency of a picture archiving and communication system (PACS) and a smartphone application, which is an educative app to easily measure sagittal balance parameters (SagittalMeter Pro), for measuring spinopelvic sagittal parameters. METHODS: Three spine surgeons measured lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) on standing posteroanterior radiographs of 30 patients using PACS and SagittalMeter Pro. Measurements were repeated a week after the original measurements. Intraobserver and interobserver variabilities and reliabilities of each parameter (LL, PI, SS, and PT) were calculated for both techniques. Comparisons were performed using the paired t-test. Results are expressed as mean ± standard deviation and P values of < 0.05 were considered significant. RESULTS: PACS to SagittalMeter Pro differences between the mean absolute values of LL, PI, SS, PT were 0.50°, 0.82°, 0.81°, 0.34°, respectively, and intraobserver and interobserver variabilities were similar. Excellent intraobserver and interobserver reliabilities were obtained for PACS and SagittalMeter Pro as demonstrated by values >0.86 and >0.84, respectively. Measurement times for PACS and SagittalMeter Pro were 36.63 ± 7.55 and 14.57 ± 1.96 seconds, respectively, and this difference was significant (P = 0.001). CONCLUSIONS: The study shows PACS and SagittalMeter Pro are equivalent in terms of their abilities to measure spinopelvic sagittal parameters, and that the time required to obtain measurements was significantly less for SagittalMeter Pro. We believe that SagittalMeter Pro may be helpful when planning spinal surgery.

Significance of Provocative Perfusion Computed Tomography for Evaluation of Bow Hunter Syndrome.

Bow hunter syndrome (BHS) is a rare vascular phenomenon of vertebrobasilar insufficiency caused by dynamic stenosis of the vertebral artery (VA) by osteophytes, fibrous bands, or disk herniation with neck rotation. We present a rare case of a patient with bilaterally patent VAs on neutral imaging and bilateral dynamic compression of VA with left head rotation. Provocation tests are critical toward understanding dynamic pathophysiology of BHS because normal neutral vascular imaging does not preclude diagnosis of BHS. Although dynamic angiography is the gold standard for diagnosis of BHS, cerebral angiography could be invasive and risky. Provocative test using perfusion computed tomography scan is a simple and noninvasive method to assess BHS on an outpatient basis.