Differences Between Esophageal and Tracheal Intubation Ultrasound View Proficiency: An Educational Study of Novice Prehospital Providers.

Objectives Airway ultrasound is now possible in the prehospital setting due to advances in ultrasound equipment portability. We questioned how well prehospital providers without prior experience could determine both esophageal and tracheal placement of an endotracheal tube in cadavers after a brief training course in ultrasound.  Methods This educational prospective study at the Simulation Center in Mayo Clinic Jacksonville Florida enrolled 50 prehospital providers. Demographic and practice background information was obtained through surveys. Each participant performed a baseline ultrasound to determine endotracheal tube placement in a cadaver that was randomly assigned to an esophageal or tracheal intubation. Participants then repeated the randomized testing after a 15-minute tutorial. Before and after overall accuracy as well as proportions of correct identification of esophageal and tracheal intubations were determined and compared using standard binomial proportion and McNemar's tests. Results  None of the participants had prior experience of performing airway ultrasound. Baseline group scores were 60% (CI 45%-74%) for overall accuracy (n=50), 55% (CI 32%-76%) for correct identification of an esophageal intubation, and 64% (CI 44%-81%) for correct tracheal detection. Baseline scores were not significantly different from standard binomial distributions. Post-test scores were 82% (CI 69%-91%) for overall accuracy, 96% (CI 80%-100%) for esophageal intubation detection, and 66.7% (CI 45%-84%) for tracheal intubation detection, with corresponding binomial p-values of <0.001, <0.001, and 0.15. P-values for McNemar's paired test for combined overall accuracy, correct esophageal detection, and correct tracheal detection were 0.04, 0.02, and 0.62, respectively. Conclusions Prehospital participants without prior ultrasound experience demonstrated significant gains in airway ultrasound proficiency after a limited introductory course. Post-training score increases were largely due to a notable increase in correct esophageal intubation detection rates. Learners did not make significant progress in correctly identifying a tracheal intubation. Airway ultrasound educational design may benefit from added emphasis on the potentially more difficult to recognize tracheal intubation view.

Techniques and Tips for Freehand Placement of C7 Pedicle Screws With Respect to Cervicothoracic Constructs: 2-Dimensional Operative Video.

We present a surgical video highlighting the technical pearls for C7 pedicle screw placement with respect to cervicothoracic constructs. Pedicle screw placement into C7 has been shown to enhance the biomechanical stability of both cervical and cervicothoracic constructs and is safe for patient related outcomes.1,2 Rod placement across the cervicothoracic junction is known to be difficult because of the variable starting point of the C7 pedicle screw, which may cause misalignment of the polyaxial heads with respect to the C7 and C6 screw heads. Using our step-wise method of anatomic screw placement, this potential pitfall is minimized. The T1 pedicle screw is placed first. The C6 lateral mass screw starting point is displaced slightly superiorly from the midpoint of the lateral mass in order to make room for the polyaxial head of the C7 pedicle screw. A small laminotomy is performed in order to find the medial border of the C7 pedicle. Palpation of the medial border allows for an approximation of the pedicle limits. The cranial-caudal angle of drilling is perpendicular to the C7 superior facet, and the medial-lateral trajectory typically falls between 15 and 20 degrees medial. Once the pedicle is cannulated, a ball-tipped probe is used to confirm intraosseous position. A rod is cut and contoured to the appropriate length of the construct. The C7 pedicle screw should capture the rod easily with slight displacement of the polyaxial head. Postinstrumentation anteroposterior and lateral fluoroscopy are performed to confirm good position of the lateral mass and pedicle screws. Patient consent was not required for this cadaveric surgical video.

The Future of Biomechanical Spine Research: Conception and Design of a Dynamic 3D Printed Cervical Myelography Phantom.

Background Three-dimensional (3D) printing is a growing practice in the medical community for patient care and trainee education as well as production of equipment and devices. The development of functional models to replicate physiologic systems of human tissue has also been explored, although to a lesser degree. Specifically, the design of 3D printed phantoms that possess comparable biomechanical properties to human cervical vertebrae is an underdeveloped area of spine research. In order to investigate the functional uses of cervical 3D printed models for replicating the complex physiologic and biomechanical properties of the human subaxial cervical spine, our institution has created a prototype that accurately reflects these properties and provides a novel method of assessing spinal canal dimensions using simulated myelography. To our knowledge, this is the first 3D printed phantom created to study these parameters. Materials and methods A de-identified cervical spine computed tomography imaging file was segmented using threshold modulation in 3D Slicer software. The subaxial vertebrae (C3-C7) of the scan were individualized by separating the facet joint spaces and uncovertebral joints within the software in order to create individual stereolithography (STL) files. Each individual vertebra was printed on an Ultimaker S5 dual-extrusion printer using white "tough" polylactic acid filament. A human cadaveric subaxial cervical spine was harvested to provide a control for our experiment. Both models were assessed and compared in flexion and extension dynamic motion grossly and fluoroscopically. The maximum angles of deformation on X-ray imaging were recorded using DICOM (Digital Imaging and Communications in Medicine) viewing software. In order to compare the ability to assess canal dimensions of the models using fluoroscopic imaging, a myelography simulation was designed. Results The cervical phantom demonstrated excellent ability to resist deformation in flexion and extension positions, attributed to the high quality of initial segmentation. The gross and fluoroscopic dynamic movement of the phantom was analogous to the cadaver model. The myelography simulator adequately demonstrated the canal dimensions in static and dynamic positions for both models. Pertinent anatomic landmarks were able to be effectively visualized for assessment of canal measurements for sagittal and transverse dimensions. Conclusions By utilizing the latest technologies in DICOM segmentation and 3D printing, our institution has created the first cervical myelography phantom for biomechanical evaluation and trainee instruction. By combining new technologies with anatomical knowledge, quality 3D printing shows great promise in becoming a standard player in the future of spinal biomechanical research.

Freehand C2 Pedicle Screw Placement: Surgical Anatomy and Operative Technique.

We present a surgical video demonstrating the anatomy and technique of freehand C2 pedicle screw placement using a cadaveric specimen and 3-dimensional simulation software. C2 pedicle screws have been shown to augment cervical constructs and provide increased biomechanical stability compared with pars screws due to the increased length and bony purchase of pedicle screws within the pedicle and vertebral body.1 The presence of vertebral artery variations within the transverse foramen may preclude pedicle screw placement, and these should be identified on preoperative imaging. The C2 pedicle can be directly palpated at the time of screw placement, which aids screw placement in cases of deformity or trauma. A freehand technique without the use of computed tomography scan guidance or intraoperative fluoroscopy decreases radiation exposure for the operator and patient and has been shown to be safe for patient-related outcomes.2-5 Complete exposure of the C2 posterior elements is key to identifying the pedicle. The trajectory is based on direct visualization of the medial and superior pedicle borders to avoid lateral or inferior breaches into the transverse foramen. A curved probe is used for access into the vertebral body, respecting the outer cortical walls of the pedicle. The intraosseous position is confirmed with a ball-tipped probe. Fluoroscopy should be performed after screw placement to confirm proper position. By accomplishing proper exposure and understanding the anatomy of the C2 pedicle, the placement of C2 pedicle screws using a freehand technique is a safe and efficient technique for high cervical fixation.

The Importance of the Pars Interarticularis as a Landmark for Safe Lumbar Pedicle Screw Placement: Technical Note.

The use of navigational adjuncts for pedicle screw placement has increased in popularity among surgeons with access to this technology. However, it remains important to have a comprehensive understanding of posterior bony element anatomy with respect to the location of the pedicle in order to ensure safe placement of pedicle screws. Proper exposure and identification of the pars interarticularis provide a helpful landmark during pedicle screw placement in order to confirm navigation accuracy and avoid misplaced instrumentation. In this technical note, we highlight the surgical anatomy of the pars interarticularis of the lumbar spine and its relationship to the lateral, inferior, and medial borders of the pedicle using diagrams and cadaveric dissections.

Safety and Accuracy of the Freehand Placement of C7 Pedicle Screws in Cervical and Cervicothoracic Constructs.

BACKGROUND:  Cervical pedicle screws are advantageous in their biomechanical stability within cervical and cervicothoracic constructs. The seventh cervical vertebra contains relatively large pedicles and has a low incidence of vertebral artery localization within the transverse foramina. The freehand technique of pedicle screw insertion is advantageous in decreasing intraoperative radiation exposure both to the patient and surgeon. In this study, we investigated the safety and accuracy of C7 pedicle screw placement at our institution utilizing an anatomic freehand technique. METHODS AND MATERIALS:  A retrospective study was performed, and 20 patients were identified who met the inclusion criteria over a five-year period (2013-2018). The C7 pedicle screw placement capability and accuracy were recorded. Accuracy was graded based upon postoperative imaging on a Grade 0-3 scale for breach assessment. Any neurologic complications related to screw placement were also recorded. RESULTS:  Successful pedicle screw placement occurred in 90% of attempts (36/40). The overall screw accuracy rate was 89% (32/36). There were four minor breaches (Grade 1) identified on CT, without neurologic complications. The fusion rate in our cohort for patients with follow up greater than eight months was 100%. CONCLUSIONS:  In our patient series, the freehand technique of C7 pedicle screw placement utilizing a small laminotomy with direct pedicle palpation appears to be a safe and accurate method for screw placement, and provides adequate biomechanical stability for cervical and cervicothoracic construct fusion.

3-Dimensional Simulation Videography for Instructional Placement of Bedside External Ventricular Drains.

We present a narrated video simulation (Video 1) using 3-dimensional anatomic software demonstrating the proper landmarks and relevant neuroanatomy for successful bedside external ventricular drain placement. External ventricular drains are commonly inserted at the bedside for emergent intracranial pressure monitoring and/or treatment of elevated intracranial pressure by cerebrospinal fluid drainage.1 Often, neurosurgical trainees perform this procedure early in their residency years.2,3 The relationship of the ventricle to the external skull landmarks may be a difficult concept to grasp for junior trainees who have had limited procedural experience. Multiple catheter passes in attempt to cannulate the ventricle are associated with increased procedural risk to the patient.2,4 Two common catheter misplacement locations leading to multiple catheter passes are lateral to the ventricle and anterior to the ventricle. In this video we highlight the relationship of the borders of the lateral ventricle to the insertion point at the skull during catheter placement. By using this resource for resident education, patient safety factors and resident procedural competence may be enhanced.

Investigation of a Cost-effective and Durable Material for Containing Ballistic Gel in the Construction of Ultrasound Phantoms.

There is significant variability in the realism, cost, and structural integrity of sonographic simulators available for use currently. A common material that is used for the production of sonographic simulators is synthetic ballistic gelatin, which requires a high melting temperature for molding. In this experiment, we investigated the structural integrity of high-density polyethylene (HDPE) when exposed to melted ballistics gel for the assimilation of a sonographic lumbar puncture simulator.

Construction of an Affordable Lumbar Neuraxial Block Model Using 3D Printed Materials.

Access to affordable 3D printing technology has resulted in increased interest in the creation of medical phantom task trainers. Recent research has validated the use of these trainers in simulation education. However, task trainers remain expensive, limiting their availability to medical training programs. We describe the construction of a low-cost task trainer using fused filament fabrication (FFF) printed spinal vertebrae placed in a synthetic gelatin matrix. Additionally, our model contains a realistic simulated ligamentum flavum, a removable silicone skin, as well as spinal fluid reservoir that provides a positive endpoint for intrathecal blocks. The total cost of this model was less than $400 USD. The time to 3D print the bony anatomic parts was approximately 26 hours. While we have not formally validated our model, initial impressions of tactile feel and realism were deemed positive by experienced anesthesia providers. Future work will focus on continued refinement of the model features and construction.

A Feasibility Study for the Production of Three-dimensional-printed Spine Models Using Simultaneously Extruded Thermoplastic Polymers.

Background Medical simulation is an emerging field for resident training. Three-dimensional printing has accelerated the development of models for spine surgical simulation. Previous models have utilized augmented infill ratios to simulate the density difference between cortical and cancellous bone; however, this does not fully account for differences in the material properties of these components of human vertebrae. In order to replicate the differences in both density and material characteristics for realistic spinal simulation, we created a three-dimensional model composed of multiple thermoplastic polymers. Materials and methods Three lumbar vertebrae and 20 C2 vertebrae models using an experimental dual material fabrication method were printed on an Ultimaker S5 3D printer. Assessment of model integrity during instrumentation as well as user tactile feedback were points of interest to determine prototype viability for educational and biomechanical use. The experimental cohort was compared with a control cohort consisting of a single material print, resin print, and polyurethane mold. Results Based on tactile feedback, the experimental dual material print (polylactic acid [PLA]/polyvinyl alcohol [PVA]) more accurately represented the sensation of in vivo instrumentation during pedicle probing, pedicle tapping, and screw placement. There were no instrumentation or material failures in the PLA/PVA experimental model cohort. Conclusions This feasibility study indicates that multiple material printing using PLA and PVA is a viable method to replicate the cortico-cancellous interface in vertebral models. This concept and design using our unique infill algorithm have not been yet reported in the medical literature. Further educational and biomechanical testing on our design is currently underway to establish this printing method as a new standard for spinal biomimetic modeling.

Development of a Novel 3D Printed Phantom for Teaching Neurosurgical Trainees the Freehand Technique of C2 Laminar Screw Placement.

BACKGROUND: 3D printed models have grown in popularity for resident training. Currently there is a paucity of simulators specifically designed for advanced cervical instrumentation. Our institution created a unique simulator for the instruction of freehand placement of C2 laminar screws using a specific 3-dimensional printing technique to replicate the corticocancellous interface. This study was designed to determine the efficacy of the simulator for teaching neurosurgical residents the freehand technique of C2 laminar screw placement. METHODS: Ten participants with different experience levels participated in the study. The participants were separated into 2 groups based on experience level. Primary outcome assessments were breach rates, screw-screw interaction, and the ability to successfully place 2 screws in 1 model. Participants were graded based on a performance scoring system, and the outcomes of the 2 groups were compared. RESULTS: All participants in the novice group showed improved technical ability on repeated use of the simulator and were able to successfully place bilateral screws by the fourth attempt. Statistical analysis indicated an association between operative experience level and successful bilateral screw placement, implying that the simulator accurately represented an in vivo intraoperative scenario. CONCLUSIONS: By utilizing our novel 3D printing production method, we have created a unique simulator for the freehand placement of C2 laminar screws. To our knowledge, this is the first report of a study investigating the use of a 3-dimensional printed simulator specifically designed to teach the freehand placement of C2 laminar screws to neurosurgical trainees.

Finding the "Sweet Spot" for C2 Root Transection in C1 Lateral Mass Exposure.

BACKGROUND: Atlantoaxial fusion often requires C2 nerve transection for complete C1 lateral mass exposure. Nerve transection is made ideally at the preganglionic segment proximal to the dorsal root ganglion to minimize the risk of postoperative dysesthesias. If the nerve is transected too proximally, cerebrospinal fluid leak may be encountered by violation of the dura and arachnoid where the sensory and motor nerve rootlets exit the subarachnoid space. In this study we aimed to quantify the length of the C2 nerve preganglionic segment using cadaveric specimens and develop a method for reliable intraoperative localization for sectioning during C1-2 arthrodesis. METHODS: Using microsurgical techniques, 16 C2 nerves from 8 frozen and injected cadaveric cervical spine specimens were dissected. Two key measurements were taken to establish a reliable method of preganglionic segment identification. The "sweet spot" for nerve transection was based on the approximate location of the midpoint of the preganglionic segment. RESULTS: The final determination of the ideal spot for C2 nerve transection using these calculations was 3 mm lateral to the medial border of the lateral mass. CONCLUSIONS: This anatomic study found remarkable consistency in the preganglionic segment length. The medial border of the lateral mass appeared to be a consistently reliable landmark for identification of the preganglionic segment of the C2 nerve root. By using relationships between known anatomic structures intraoperatively, safety of atlantoaxial fixation can be optimized to maximize complication avoidance and satisfactory patient outcomes.

Utilization of simulation for the introduction of new software technology to the clinical setting.

INTRODUCTION: ProVation Medical documentation software was introduced in our Department of Gastroenterology (GI). We evaluated the use of a simulation module to improve the introduction of new documentation software into a tertiary care center GI department. MATERIALS AND METHODS: Train-the-trainer education was provided by the vendor of the new documentation module. A simulation module was developed to simulate the preparatory, intraprocedural, and postprocedure phase of active utilization of the software. A standardized patient (SP)/medical actor was used for provision of data to be entered in to the ProVation Medical preprocedure module. A procedural suite was configured to allow for staff to assume their roles during endoscopic cases. A checklist of key activities was used by observers during the training. A postscenario evaluation document was collected for perceptions of training. RESULTS: Twenty-one GI nurses and technicians spent 3 hours in groups of 7 over a 3-day period completing activities commensurate with these procedural phases. Nineteen of 21 learners felt the simulation was nonthreatening, and the same number gave the course an overall 5/5 rating. There were no specimen labeling errors, patient identification errors, or sentinel events related to the software rollout. All learners felt that physician involvement in the simulation would have been beneficial. CONCLUSIONS: Simulation can be used to improve the rollout of new software in a tertiary care center. Staff satisfaction associated with this type of learning activity was high, and a communicated level of comfort was achieved as a result of the simulation-based experiential learning.