Diagnosis and Management of Cerebral Venous Thrombosis: A Scientific Statement From the American Heart Association.

Cerebral venous thrombosis accounts for 0.5% to 3% of all strokes. The most vulnerable populations include young individuals, women of reproductive age, and patients with a prothrombotic state. The clinical presentation of cerebral venous thrombosis is diverse (eg, headaches, seizures), requiring a high level of clinical suspicion. Its diagnosis is based primarily on magnetic resonance imaging/magnetic resonance venography or computed tomography/computed tomographic venography. The clinical course of cerebral venous thrombosis may be difficult to predict. Death or dependence occurs in 10% to 15% of patients despite intensive medical treatment. This scientific statement provides an update of the 2011 American Heart Association scientific statement for the diagnosis and management of cerebral venous thrombosis. Our focus is on advances in the diagnosis and management decisions of patients with suspected cerebral venous thrombosis. We discuss evidence for the use of anticoagulation and endovascular therapies and considerations for craniectomy. We also provide an algorithm to optimize the management of patients with cerebral venous thrombosis and those with progressive neurological deterioration or thrombus propagation despite maximal medical therapy.

Editor's Choice - Peri-Operative Outcomes of Carotid Endarterectomy are Not Improved on Dual Antiplatelet Therapy vs. Aspirin Monotherapy: A Systematic Review and Meta-Analysis.

OBJECTIVE: A systematic review and meta-analysis of the peri-operative outcomes of carotid endarterectomy (CEA) on dual antiplatelet therapy (DAPT) vs. aspirin monotherapy was carried out, to determine optimal peri-operative management with these antiplatelet agents. DATA SOURCES: The Web of Science, Pubmed, and Embase databases were searched from inception to July 2021. The corresponding authors of excluded articles were contacted to obtain additional data for possible inclusion. REVIEW METHODS: The main outcomes included ischaemic complications (stroke, transient ischaemic attack [TIA], and transcranial Doppler [TCD] measured micro-emboli), haemorrhagic complications (haemorrhagic stroke, neck haematoma, and re-operation for bleeding), and composite outcomes. Pooled estimates using odds ratios (ORs) were combined using a random or fixed effects model based on the results of the chi square test and calculation of I2. RESULTS: In total, 47 411 patients were included in 11 studies, with 14 345 (30.2%) receiving DAPT and 33 066 (69.7%) receiving aspirin only. There was no significant difference in the rates of peri-operative stroke (OR 0.87, 95% confidence interval [CI] 0.72 - 1.05) and TIA (OR 0.78, 95% CI 0.52 - 1.17) despite a significant reduction in TCD measured micro-emboli (OR 0.19, 95% CI 0.10 - 0.35) in the DAPT compared with the aspirin monotherapy group. Subgroup analysis did not reveal any significant difference in ischaemic stroke risk between patients with asymptomatic and symptomatic carotid artery stenosis. DAPT was associated with an increased risk of neck haematoma (OR 2.79, 95% CI 1.87 - 4.18) and re-operation for bleeding (OR 1.98, 95% CI 1.77 - 2.23) vs. aspirin. Haemorrhagic stroke was an under reported outcome in the literature. CONCLUSION: This meta-analysis found that CEA while on DAPT increased the risk of haemorrhagic complications, with similar rates of ischaemic complications, vs. aspirin monotherapy. This suggests that the risks of performing CEA on DAPT outweigh the benefits, even in patients with symptomatic carotid stenosis. The overall quality of studies was low, and improved reporting of CEA outcomes in the literature is necessary.

Endovascular and Antithrombotic Treatment in Blunt Cerebrovascular Injuries: A Systematic Review and Meta-Analysis.

OBJECTIVES: Ischemic stroke has been estimated to occur in up to 26% of patients with blunt cerebrovascular injury (BCVI). Antithrombotic therapy (AT) may be used for stroke prevention, but the role of endovascular treatment (ET) remains unclear. We systematically reviewed the literature on AT and ET for the treatment of patients with BCVIs. MATERIALS AND METHODS: PubMed, EMBASE, Web of Science, and Cochrane were searched upon the PRISMA guidelines to include studies reporting the use of ET in BCVI patients. Post-ET neurologic outcomes, radiographic responses, and complication rates were assessed. A fixed-effect model meta-analysis was performed to compare treatment-related post-BCVI ischemic stroke rates between AT and ET protocols. RESULTS: We included 16 studies comprising 352 patients undergoing ET for BCVI. Mean post-ET rates of good neurologic outcomes and radiologic responses were 86.9% (range, 63.6-100%) and 94.0% (range 57.1-100%), respectively. Mean post-ET complication rate was 5.2% (range, 0-66.7%). Seven studies compared the roles of AT (delivered in 805 patients) and ET (performed in 235 patients) for preventing the onset of post-BCVI ischemic strokes. No significant difference in rates of post-BCVI ischemic stroke was found between patients receiving AT vs patients undergoing ET (OR 0.71, 95% CI: 0.35-1.42, p = 0.402). CONCLUSION: AT and ET may be comparable in preventing the occurrence of ischemic stroke following BCVIs. AT may be preferred as the less-invasive first-line therapy, but ET showed favorable rates of post-treatment clinical and radiologic outcomes, coupled with low rates of treatment-related complications.

Access-site complications in ultrasound-guided endovascular thrombectomy: a single-institution retrospective cohort study.

OBJECTIVE: Mechanical endovascular thrombectomy (EVT) is an increasingly relied-on treatment for clot retrieval in the context of ischemic strokes, which otherwise are associated with significant morbidity and mortality. Despite several known risks associated with this procedure, there is a high degree of technical heterogeneity across both centers and operators. The most common procedural complications occur at the point of transfemoral access (the common femoral artery), and include access-site hematomas, dissections, and pseudoaneurysms. Other interventional fields have previously popularized the use of ultrasound to enhance the anatomical localization of structures relevant to vascular access and thereby reducing access-site complications. In this study, the authors aimed to describe the ultrasound-guided EVT technique performed at a large, quaternary neurovascular referral center, and to characterize the effects of ultrasound guidance on access-site complications. METHODS: A retrospective chart review of all patients treated with EVT at a single center between January 2013 and August 2020 was performed. Patients in this cohort were treated using a universal, unique, ultrasound-guided, single-wall puncture technique, which bears several theoretical advantages over the standard technique of arterial puncture via palpation. RESULTS: There were 479 patients treated with EVT within the study period. Twenty patients in the cohort were identified as having experienced some form of access-site complication. Eight (1.67%) of these patients experienced minor access-site complications, all of which were groin hematomas and none of which were clinically significant, as defined by requiring surgical or interventional management or transfusion. The remaining 12 patients experienced arterial dissection (n = 5), arterial pseudoaneurysm (n = 4), retroperitoneal hematoma (n = 2), or arterial occlusion (n = 1), with only 1.04% (5/479) requiring surgical or interventional management or transfusion. CONCLUSIONS: The authors found an overall reduction in total access-site complications as well as minor access-site complications in the study cohort compared with previously published randomized controlled trials and observational studies in the recent literature. The findings suggested that there may be a role for routine use of ultrasound-guided puncture techniques in EVT to decrease rates of complications.

Outcomes of Endovascular Thrombectomy for Basilar Artery Occlusion.

BACKGROUND AND PURPOSE: Large prospective observational studies have cast doubt on the common assumption that endovascular thrombectomy (EVT) is superior to intravenous thrombolysis for patients with acute basilar artery occlusion (BAO). The purpose of this study was to retrospectively review our experience for patients with BAO undergoing EVT with modern endovascular devices. METHODS: All consecutive patients undergoing EVT with either a second-generation stent retriever or direct aspiration thrombectomy for BAO at our regional stroke center from January 1, 2013 to March 1, 2019 were included. The primary outcome measure was functional outcome at 1 month using the modified Rankin Scale (mRS) score. Multivariable logistic regression was used to assess the association between patient characteristics and dichotomized mRS. RESULTS: A total of 43 consecutive patients underwent EVT for BAO. The average age was 67 years with 61% male patients. Overall, 37% (16/43) of patients achieved good functional outcome. Successful reperfusion was achieved in 72% (31/43) of cases. The median (interquartile range) stroke onset to treatment time was 420 (270-639) minutes (7 hours) for all patients. The procedure-related complication rate was 9% (4/43). On multivariate analysis, posterior circulation Alberta stroke program early computed tomography score and Basilar Artery on Computed Tomography Angiography score were associated with improved functional outcome. CONCLUSION: EVT appears to be safe and feasible in patients with BAO. Our finding that time to treatment and successful reperfusion were not associated with improved outcome is likely due to including patients with established infarcts. Given the variability of collaterals in the posterior circulation, the paradigm of utilizing a tissue window may assist in patient selection for EVT. Magnetic resonance imaging may be a reasonable option to determine the extent of ischemia in certain situations.

Utilization of Spinal Intra-operative Three-dimensional Navigation by Canadian Surgeons and Trainees: A Population-based Time Trend Study.

BACKGROUND: Computer-assisted navigation (CAN) improves the accuracy of spinal instrumentation in vertebral fractures and degenerative spine disease; however, it is not widely adopted because of lack of training, high capital costs, workflow hindrances, and accuracy concerns. We characterize shifts in the use of spinal CAN over time and across disciplines in a single-payer health system, and assess the impact of intra-operative CAN on trainee proficiency across Canada. METHODS: A prospectively maintained Ontario database of patients undergoing spinal instrumentation from 2005 to 2014 was reviewed retrospectively. Data were collected on treated pathology, spine region, surgical approach, institution type, and surgeon specialty. Trainee proficiency with CAN was assessed using an electronic questionnaire distributed across 15 Canadian orthopedic surgical and neurosurgical programs. RESULTS: In our provincial cohort, 16.8% of instrumented fusions were CAN-guided. Navigation was used more frequently in academic institutions (15.9% vs. 12.3%, p<0.001) and by neurosurgeons than orthopedic surgeons (21.0% vs. 12.4%, p<0.001). Of residents and fellows 34.1% were fully comfortable using spinal CAN, greater for neurosurgical than orthopedic surgical trainees (48.1% vs. 11.8%, p=0.008). The use of CAN increased self-reported proficiency in thoracic instrumentation for all trainees by 11.0% (p=0.036), and in atlantoaxial instrumentation for orthopedic trainees by 18.0% (p=0.014). CONCLUSIONS: Spinal CAN is used most frequently by neurosurgeons and in academic centers. Most spine surgical trainees are not fully comfortable with the use of CAN, but report an increase in technical comfort with CAN guidance particularly for thoracic instrumentation. Increased education in spinal CAN for trainees, particularly at the fellowship stage and, specifically, for orthopedic surgery, may improve adoption.

CONTEXTE: La chirurgie assistée par ordinateur (CAO) permet d'améliorer la précision de l'exploration instrumentale employée dans le cas de fractures vertébrales et de maladies dégénératives de la colonne vertébrale. Cela dit, elle n'a pas encore été adoptée à grande échelle en raison d'un manque de formation, de coûts d'immobilisation considérables, d'obstacles liés à l'organisation du travail et de doutes quant à son exactitude. C'est dans cette perspective que nous voulons décrire, parmi divers champs de pratique, les transformations se rapportant au fil du temps à l'utilisation de la CAO de la colonne vertébral dans le cadre d'un régime de santé universel à payeur unique. Qui plus est, nous voulons aussi évaluer l'impact de la CAO en ce qui a trait aux compétences des stagiaires partout au Canada. MÉTHODES: Pour ce faire, nous avons passé en revue de façon rétrospective une base de données tenue à jour prospectivement au sujet de patients ontariens ayant été soumis de 2005 à 2014 à une exploration instrumentale de la colonne vertébrale. Les données obtenues portaient sur le type de pathologie traitée, sur la région de la colonne vertébrale visée, sur l'approche chirurgicale privilégiée, sur le type d'établissement et sur la spécialité du chirurgien ayant intervenu. Les compétences des stagiaires en matière de CAO ont également été évaluées à l'aide d'un questionnaire en ligne diffusé au sein de 15 programmes canadiens de chirurgie orthopédique et de neurochirurgie. RÉSULTATS: En tout, 16,8 % des fusions instrumentées réalisées au sein de notre cohorte ontarienne l'ont été à l'aide de la technique de la CAO. Cette dernière a été utilisée plus fréquemment dans des établissements d'enseignement universitaire (15,9 % par opposition à 12,3 % pour les autres; p<0,001) mais aussi plus souvent par des neurochirurgiens (21,0 % par opposition à 12,4 % par des chirurgiens orthopédiques; p<0,001). En outre, 34,1 % des résidents et des médecins suivant une formation complémentaire étaient parfaitement à l'aise dans l'utilisation de la CAO de la colonne vertébrale (48,1 % de ceux se spécialisant en neurochirurgie par opposition à 11,8 % de ceux se spécialisant en chirurgie orthopédique; p = 0,008). L'utilisation de la CAO a par ailleurs entraîné une augmentation, auto-déclarée, de 11,0 % de l'aptitude à faire usage de l'exploration instrumentale thoracique chez tous les stagiaires (p = 0,036); dans le cas de l'exploration instrumentale atlanto-axiale, cette augmentation a été de 18,0 % (p = 0,014) chez les stagiaires en chirurgie orthopédique. CONCLUSIONS: La CAO de la colonne vertébrale est employée le plus souvent par les neurochirurgiens dans des établissements d'enseignement universitaire. La plupart des stagiaires en chirurgie de la colonne vertébrale ne sont pas entièrement à l'aise en ce qui concerne l'utilisation de la CAO. Toutefois, ils ont signalé une augmentation de leur aisance à utiliser la CAO et à bénéficier de son assistance, en particulier dans des cas d'exploration instrumentale thoracique. En somme, une plus ample formation en matière de CAO de la colonne vertébrale offerte aux stagiaires, particulièrement à ceux suivant une formation complémentaire et dans le champ de la chirurgie orthopédique, pourrait favoriser son adoption.

Differential phase standard-deviation-based optical coherence tomographic angiography for human retinal imaging in vivo.

We present a differential phase standard-deviation (DPSD)-based optical coherence tomographic (OCT) angiography (OCTA) technique to calculate the angiography images of the human retina. The standard deviation was calculated along the depth direction on the differential phase image of two B-scans (from the same position, at different times) to contrast dynamic vascular signals. The performance of a DPSD was verified by both phantom and in vivo experiments. When compared to other OCTA algorithms such as phase variance OCT, speckle variance OCT, and optical microangiography, we showed that a DPSD achieved improved image contrast and higher sensitivity. Furthermore, we also found the improved signal-to-noise ratio and contrast-to-noise ratio of 1.6 dB and 0.5, respectively, in large scanning range images.

Single-pass endovascular thrombectomy for massive carotid-cerebral occlusion.

Acute concomitant occlusions of the extracranial internal carotid artery and intracranial vessels frequently require multiple passes with stent-retrievers for mechanical thrombectomy. Due to the large clot burden associated with these occlusions, their response to intravenous thrombolysis is poor. We herein report a successful case of evacuating a massive clot (>14 cm) in a single-pass using a stent-retrieval device.

High speed, wide velocity dynamic range Doppler optical coherence tomography (Part V): Optimal utilization of multi-beam scanning for Doppler and speckle variance microvascular imaging.

In this paper, a multi-beam scanning technique is proposed to optimize the microvascular images of human skin obtained with Doppler effect based methods and speckle variance processing. Flow phantom experiments were performed to investigate the suitability for combining multi-beam data to achieve enhanced microvascular imaging. To our surprise, the highly variable spot sizes (ranging from 13 to 77 µm) encountered in high numerical aperture multi-beam OCT system imaging the same target provided reasonably uniform Doppler variance and speckle variance responses as functions of flow velocity, which formed the basis for combining them to obtain better microvascular imaging without scanning penalty. In vivo 2D and 3D imaging of human skin was then performed to further demonstrate the benefit of combining multi-beam scanning to obtain improved signal-to-noise ratio (SNR) in microvascular imaging. Such SNR improvement can be as high as 10 dB. To our knowledge, this is the first demonstration of combining different spot size, staggered multiple optical foci scanning, to achieve enhanced SNR for blood flow OCT imaging.

Augmented Reality in Neurosurgery: A Review of Current Concepts and Emerging Applications.

Augmented reality (AR) superimposes computer-generated virtual objects onto the user's view of the real world. Among medical disciplines, neurosurgery has long been at the forefront of image-guided surgery, and it continues to push the frontiers of AR technology in the operating room. In this systematic review, we explore the history of AR in neurosurgery and examine the literature on current neurosurgical applications of AR. Significant challenges to surgical AR exist, including compounded sources of registration error, impaired depth perception, visual and tactile temporal asynchrony, and operator inattentional blindness. Nevertheless, the ability to accurately display multiple three-dimensional datasets congruently over the area where they are most useful, coupled with future advances in imaging, registration, display technology, and robotic actuation, portend a promising role for AR in the neurosurgical operating room.

Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 µJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

A simple method for controlled reduction duraplasty during cranioplasty.

BACKGROUND: Bone flap re-approximation during cranioplasty can be complicated by underlying pseudomeningocele or meningoencephalocele. A technique for controlled reduction duraplasty to aid bone flap positioning is suggested. METHODS: A simple method using bipolar electrocautery in a predetermined radial pattern from the center of defect is described. Localized tissue contraction allows controlled reduction in the surface area and degree of protrusion. This in turn facilitates bone flap positioning. RESULTS: The main advantage of this technique is slow and evenly distributed pressure conferred by controlled tissue contraction using multiple radial coagulation lines. No technical difficulties or complications have occurred with this method during cranioplasty for 11 patients. CONCLUSION: This simple technique for controlled reduction duraplasty can provide an easy and efficient method for bone flap re-approximation, and add to the existing techniques for a commonly performed procedure.

High speed, wide velocity dynamic range Doppler optical coherence tomography (Part IV): split spectrum processing in rotary catheter probes.

We report a technique for blood flow detection using split spectrum Doppler optical coherence tomography (ssDOCT) that shows improved sensitivity over existing Doppler OCT methods. In ssDOCT, the Doppler signal is averaged over multiple sub-bands of the interferogram, increasing the SNR of the Doppler signal. We explore the parameterization of this technique in terms of number of sub-band windows, width and overlap of the windows, and their effect on the Doppler signal to noise in a flow phantom. Compared to conventional DOCT, ssDOCT processing has increased flow sensitivity. We demonstrate the effectiveness of ssDOCT in-vivo for intravascular flow detection within a porcine carotid artery and for microvascular vessel detection in human pulmonary imaging, using rotary catheter probes. To our knowledge, this is the first report of visualizing in-vivo Doppler flow patterns adjacent to stent struts in the carotid artery.

Fiber-optic polarization diversity detection for rotary probe optical coherence tomography.

We report a polarization diversity detection scheme for optical coherence tomography with a new, custom, miniaturized fiber coupler with single mode (SM) fiber inputs and polarization maintaining (PM) fiber outputs. The SM fiber inputs obviate matching the optical lengths of the X and Y OCT polarization channels prior to interference and the PM fiber outputs ensure defined X and Y axes after interference. Advantages for this scheme include easier alignment, lower cost, and easier miniaturization compared to designs with free-space bulk optical components. We demonstrate the utility of the detection system to mitigate the effects of rapidly changing polarization states when imaging with rotating fiber optic probes in Intralipid suspension and during in vivo imaging of human airways.

Temperature-compensated fiber-optic 3D shape sensor based on femtosecond laser direct-written Bragg grating waveguides.

Temperature-compensated 3D fiber shape sensing is demonstrated with femtosecond laser direct-written optical and Bragg grating waveguides that were distributed axially and radially inside a single coreless optical fiber. Efficient light coupling between the laser-written optical circuit elements and a standard single-mode fiber (SMF) was obtained for the first time by 3D laser writing of a 1 × 3 directional coupler to meet with the core waveguide in the fusion-spliced SMF. Simultaneous interrogation of nine Bragg gratings, distributed along three laterally offset waveguides, is presented through a single waveguide port at 1 kHz sampling rate to follow the Bragg wavelength shifts in real-time and thereby infer shape and temperature profile unambiguously along the fiber length. This distributed 3D strain and thermal sensor is freestanding, flexible, compact, lightweight and opens new directions for creating fiber cladding photonic devices for a wide range of applications from shape and thermal sensing to guidance of biomedical catheters and tools in minimally invasive surgery.

Hybrid intravascular ultrasound and optical coherence tomography catheter for imaging of coronary atherosclerosis.

OBJECTIVE: To demonstrate the feasibility of imaging human coronary atherosclerosis using a novel hybrid intravascular ultrasound (IVUS) and optical coherence tomography (OCT) imaging catheter. BACKGROUND: IVUS and OCT have synergistic advantages and recent studies involving both modalities suggest the use of a hybrid imaging catheter may offer improved guidance of coronary interventions and plaque characterization. METHODS: A 1.3 m custom hybrid IVUS-OCT imaging probe was built within a 4F catheter using a 42 MHz ultrasound transducer and an OCT imaging fiber. Coplanar images were simultaneously acquired ex vivo by both modalities in 31 arterial segments from 11 cadaveric human coronaries. IVUS and OCT images were acquired at 250 µm intervals, of which 13 of the arterial segments were selected as representative of a diverse set of pathological findings. The selected segments were then imaged with either digital X-ray or micro-CT, processed for histological analysis and compared with the corresponding IVUS and OCT images. RESULTS: Images of human coronary atherosclerosis using the hybrid IVUS-OCT catheter demonstrated a range of vascular pathologies that were confirmed on histology. The anticipated synergistic advantages of each modality were qualitatively apparent, including the deeper tissue penetration of IVUS and the superior contrast, resolution and near-field image quality of OCT. CONCLUSIONS: Preliminary ex vivo images using a hybrid IVUS-OCT catheter demonstrated feasibility in using the device for intracoronary imaging of atherosclerosis. Future studies will include in vivo imaging and larger samples sizes to enable quantitative comparisons of tissue characterization and feature identification using hybrid imaging catheters versus standalone IVUS and OCT imaging techniques. © 2012 Wiley Periodicals, Inc.

The pedicle screw accuracy using a robotic system and measured by a novel three-dimensional method.

Robotics in medicine is associated with precision, accuracy, and replicability. Several robotic systems are used in spine surgery. They are all considered shared-control systems, providing "steady-hand" manipulation instruments. Although numerous studies have testified to the benefits of robotic instrumentations, they must address their true accuracy. Our study used the Mazor system under several situations and compared the spatial accuracy of the pedicle screw (PS) insertion and its planned trajectory. We used two cadaveric specimens with intact spinal structures from C7 to S1. PS planning was performed using the two registration methods (preopCT/C-arm or CT-to-fluoroscopy registration). After planning, the implant spatial orientation was defined based on six anatomic parameters using axial and sagittal CT images. Two surgical open and percutaneous access were used to insert the PS. After that, another CT acquisition was taken. Accuracy was classified into optimal, inaccurate and unacceptable according to the degree of screw deviation from its planning using the same spatial orientation method. Based on the type of spatial deviation, we also classified the PS trajectory into 16 pattern errors. Seven (19%) out of 37 implanted screws were considered unacceptable (deviation distances > 2.0 mm or angulation > 5°), and 14 (38%) were inaccurate (> 0.5 mm and ≤ 2.0 mm or > 2.5° and ≤ 5°). CT-to-fluoroscopy registration was superior to preopCT/C-arm (average deviation in 0.9 mm vs. 1.7 mm, respectively, p < 0.003), and percutaneous was slightly better than open but did not reach significance (1.3 mm vs. 1.7 mm, respectively). Regarding pattern error, the tendency was to have more axial than sagittal shifts. Using a quantitative method to categorize the screw 3D position, only 10.8% of the screws were considered unacceptable. However, with a more rigorous concept of inaccuracy, almost half were non-optimal. We also identified that, unlike some previous results, the O-arm registration delivers more accurate implants than the preopCT/C-arm method.