International Learner Perceptions, Educational Value, and Cost Associated With the Use of Start-to-Finish Surgical Simulation Compared With Cadaveric Models.

BACKGROUND: Graduate surgical education is highly variable across regions and institutions regarding case volume and degree of trainee participation in each case. Dedicated educational curriculum using cadaveric tissue has been shown to enhance graduate surgical training, however with associated financial and utility burden to the institution. OBJECTIVE: To investigate the utility of educational and cost applications of a novel method of combining mixed organic hydrogel polymers and 3-dimensional printed anatomic structures to create a complete "start-to-finish" simulation for resident education in spinal anatomy, instrumentation, and surgical techniques. METHODS: This qualitative pilot study investigated 14 international participants on achievement of objective and personal learning goals in a standardized curriculum using biomimetic simulation compared with cadaveric tissue. A questionnaire was developed to examine trainee evaluation of individual anatomic components of the biomimetic simulators compared with previous experience with cadaveric tissue. RESULTS: A total of 210 responses were acquired from 14 participants. Six participants originated from US residency education programs and 8 from transcontinental residency programs. Survey results for the simulation session revealed high user satisfaction. Score averages for each portion of the simulation session indicated learner validation of anatomic features for the simulation compared with previous cadaveric experience. Cost analysis resulted in an estimated savings of $10 833.00 for this single simulation session compared with previous cadaveric tissue sessions. CONCLUSION: The results of this study indicate a strong potential of establishing biomimetic simulation as a cost-effective and high-quality alternative to cadaveric tissue for the instruction of fundamental spine surgical techniques.

An Anatomical Method for Rib Disconnection During Posterior Costotransversectomy for Paravertebral Access to the Ventral Thoracic Spine.

OBJECTIVE: Posterior costotransversectomy in the thoracic spine is commonly used for degenerative diseases, tumors, trauma, and other operative indications. It involves resection of the rib head after the ligamentous complexes have been disconnected from the transverse process and lateral vertebral body. The current literature provides only vague descriptions of the steps involved in rib disconnection with respect to posterior costotransversectomy. METHODS AND RESULTS: Through cadaveric studies and in vivo application, a stepwise method for rib disconnection is described. CONCLUSIONS: This manuscript is the first to outline an anatomical method for rib disconnection during costotransversectomy.

Investigation of a three-dimensional printed dynamic cervical spine model for anatomy and physiology education.

INTRODUCTION: Three-dimensional (3D) printing of anatomical structures is a growing method of education for students and medical trainees. These models are generally produced as static representations of gross surface anatomy. In order to create a model that provides educators with a tool for demonstration of kinematic and physiologic concepts in addition to surface anatomy, a high-resolution segmentation and 3D-printingtechnique was investigated for the creation of a dynamic educational model. METHODS: An anonymized computed tomography scan of the cervical spine with a diagnosis of ossification of the posterior longitudinal ligament was acquired. Using a high-resolution thresholding technique, the individual facet and intervertebral spaces were separated, and models of the C3-7 vertebrae were 3D-printed. The models were placed on a myelography simulator and subjected to flexion and extension under fluoroscopy, and measurements of the spinal canal diameter were recorded and compared to in-vivo measurements. The flexible 3D-printed model was then compared to a static 3D-printed model to determine the educational benefit of demonstrating physiologic concepts. RESULTS: The canal diameter changes on the flexible 3D-printed model accurately reflected in-vivo measurements during dynamic positioning. The flexible model also was also more successful in teaching the physiologic concepts of spinal canal changes during flexion and extension than the static 3D-printed model to a cohort of learners. CONCLUSIONS: Dynamic 3D-printed models can provide educators with a cost-effective and novel educational tool for not just instruction of surface anatomy, but also physiologic concepts through 3D ex-vivo modeling of case-specific physiologic and pathologic conditions.

Establishing a Cost-Effective 3-Dimensional Printing Laboratory for Anatomical Modeling and Simulation: An Institutional Experience.

SUMMARY STATEMENT: Three-dimensional (3D) printing is rapidly growing in popularity for anatomical modeling and simulation for medical organizations across the world. Although this technology provides a powerful means of creating accurately representative models of anatomic structures, there remains formidable financial and workforce barriers to understanding the fundamentals of technology use, as well as establishing a cost- and time-effective system for standardized incorporation into a workflow for simulator design and anatomical modeling. There are many factors to consider when choosing the appropriate printer and accompanying software to succeed in accomplishing the desired goals of the executing team. The authors have successfully used open-access software and desktop fused deposition modeling 3D printing methods to produce more than 1000 models for anatomical modeling and procedural simulation in a cost-effective manner. It is our aim to share our experience and thought processes of implementing 3D printing into our anatomical modeling and simulation workflow to encourage other institutions to comfortably adopt this technology into their daily routines.

Investigation of the "Superior Facet Rule" Using 3D-Printed Thoracic Vertebrae With Simulated Corticocancellous Interface.

BACKGROUND: Pedicle screw placement is the most common method of fixation in the thoracic spine. Use of the "superior facet rule" allows the operator to locate the borders of the pedicle reliably using posterior landmarks alone. This study investigated the ability of 3-dimensionally (3D)-printed thoracic vertebrae, made from combined thermoplastic polymers, to demonstrate pedicle screw cannulation accurately using the superior facet as a reliable landmark. METHODS: An anonymized computed tomography scan of the thoracic spine was obtained. The T1-T12 thoracic vertebrae were anatomically segmented and 3D-printed. The pedicle diameters and distance from the midpoint of the superior facet to the ventral lamina were recorded. A total of 120 thoracic pedicles in 60 thoracic vertebral models were instrumented using a freehand technique based only on posterior landmarks. The vertebral models were then coronally cut and examined for medial or lateral violations of the pedicle after screw placement. RESULTS: A total of 120 pedicle screws were placed successfully within the 3D-printed thoracic vertebral models. Average measurements fell within 1 standard deviation of previous population studies. There were no pedicle wall violations using standard posterior element landmarks for instrumentation. There were 3 lateral violations of the vertebral body wall during screw placement, all attributable to the insertion technique. CONCLUSIONS: 3D-printed thoracic vertebral models using combined thermoplastic polymers can accurately demonstrate the anatomical ultrastructure and posterior element relationships of the superior facet rule for safe thoracic pedicle screw placement. This method of vertebral model prototyping could prove useful for surgical education and demonstrating spinal anatomy.

Total Anterior Uncinatectomy During Anterior Discectomy and Fusion for Recurrent Cervical Radiculopathy: A Two-dimensional Operative Video and Technical Report.

A common cause of cervical radiculopathy from degenerative foraminal stenosis is severe uncovertebral hypertrophy. It is difficult to accomplish complete foraminal decompression in these cases with posterior techniques without the removal of a large portion of the facet joint. Total removal of the uncovertebral joint from an anterior approach allows for complete decompression of the exiting cervical nerve root and has been shown to be a safe technique. In this surgical video and technical report, we demonstrate the surgical anatomy and operative technique of a two-level anterior uncinatectomy during anterior discectomy and fusion (ACDF) for recurrent cervical radiculopathy after a previous multi-level posterior foraminotomy. The patient is a 67-year-old male with a progressive left arm and neck pain with radiographic, clinical, and electrophysiologic diagnostic evidence of active C6 and C7 radiculopathies from degenerative foraminal stenosis at the C5-6 and C6-7 levels. Posterior foraminotomies had been performed without significant improvement in his radicular pain. A repeat MRI demonstrated lateral foraminal stenosis from severe uncovertebral joint hypertrophy at the C5-6 and C6-7 levels. After acquiring informed consent from the patient, an anterior approach was performed with complete removal of the uncovertebral joints at both levels with discectomy and fusion. Postoperatively, the patient had complete resolution of his radicular pain and remained pain-free at the latest follow-up. Complete uncinatectomy and ACDF is an effective technique for complete foraminal decompression in cases of refractory radiculopathy and neck pain after unsuccessful posterior decompression.

The SpineBox: A Freely Available, Open-access, 3D-printed Simulator Design for Lumbar Pedicle Screw Placement.

Background The recent COVID-19 pandemic has demonstrated the need for innovation in cost-effective and easily produced surgical simulations for trainee education that are not limited by physical confines of location. This can be accomplished with the use of desktop three-dimensional (3D) printing technology. This study describes the creation of a low-cost and open-access simulation for anatomical learning and pedicle screw placement in the lumbar spine, which is termed the SpineBox. Materials and methods An anonymized CT scan of the lumbar spine was obtained and converted into 3D software files of the L1-L5 vertebral bodies. A computer-assisted design (CAD) software was used to assemble the vertebral models into a simulator unit in anatomical order to produce an easily prototyped simulator. The printed simulator was layered with foam in order to replicate soft tissue structures. The models were instrumented with pedicle screws using standard operative technique and examined under fluoroscopy. Results Ten SpineBoxes were created using a single desktop 3D printer, with accurate replication of the cortico-cancellous interface using previously validated techniques. The models were able to be instrumented with pedicle screws successfully and demonstrated quality representation of bony structures under fluoroscopy. The total cost of model production was under $10. Conclusion The SpineBox represents the first open-access simulator for the instruction of spinal anatomy and pedicle screw placement. This study aims to provide institutions across the world with an economical and feasible means of spine surgical simulation for neurosurgical trainees and to encourage other rapid prototyping laboratories to investigate innovative means of creating educational surgical platforms in the modern era.

Microanatomical considerations for safe uncinate removal during anterior cervical discectomy and fusion: 10-year experience.

Cervical radiculopathy from uncovertebral joint (UVJ) hypertrophy and nerve root compression often occurs anterior and lateral within the cervical intervertebral foramen, presenting a challenge for complete decompression through anterior cervical approaches owing to the intimate association with the vertebral artery and associated venous plexus. Complete uncinatectomy during anterior cervical discectomy and fusion (ACDF) is a controversial topic, many surgeons relying on indirect nerve root decompression from restoration of disc space height. However, in cases of severe UVJ hypertrophy, indirect decompression does not adequately address the underlying pathophysiology of anterolateral foraminal stenosis. Previous reports in the literature have described techniques involving extensive dissection of the cervical transverse process and lateral uncinate process (UP) in order to identify the vertebral artery for safe removal of the UP. Recent anatomical investigations have detailed the microanatomical organization of the fibroligamentous complex surrounding the UP and neurovascular structures. The use of the natural planes formed from the encapsulation of these connective tissue layers provides a safe passage for lateral UP dissection during anterior cervical approaches. This can be performed from within the disc space during ACDF to avoid extensive lateral dissection. In this article, we present our 10-year experience using an anatomy-based microsurgical technique for safe and complete removal of the UP during ACDF for cervical radiculopathy caused by UVJ hypertrophy.

Investigation and Feasibility of Combined 3D Printed Thermoplastic Filament and Polymeric Foam to Simulate the Cortiocancellous Interface of Human Vertebrae.

Disorders of the spine are among the most common indications for neurosurgical and orthopedic surgical interventions. Spinal fixation in the form of pedicle screw placement is a common form of instrumentation method in the lower cervical, thoracic, and lumbar spine. A vital principle to understand for the safe and accurate placement of pedicle screws is the palpable difference between the cortical and cancellous bone, both of which have different material properties and compositions. Probing and palpation of the hard cortical bone, also known as the "ventral lamina", covering the neural elements of the spinal canal during screw placement provides manual feedback to the surgeon, indicating an impending breach if continued directional force is applied. Generally, this practice is learned at the expense of patients in live operating room scenarios. Currently, there is a paucity of human vertebra simulation designs that have been validated based on the in vivo ultrastructure and physical properties of human cortical and cancellous bone. In this study, we examined the feasibility of combining three-dimensionally printed thermoplastic polymers with polymeric foam to replicate both the vertebral corticocancellous interface and surface anatomy for procedural education.

Biomimetic 3-Dimensional-Printed Posterior Cervical Laminectomy and Fusion Simulation: Advancements in Education Tools for Trainee Instruction.

Surgical proficiency is classically acquired through live experience in the operating room. Trainee exposure to cases and complex pathologies is highly variable between training programs.1 Currently, there is no standard for neurosurgical skill assessment for specific operative techniques for trainees. Cadaveric simulation has been used to demonstrate surgical technique and assess resident skill but often presents a significant financial and facility burden.2-4 Three-dimensional (3D) printing is an alternative to cadaveric tissue in providing high-quality representation of surgical anatomy; however, this technology has significant limitations in replicating conductive soft tissue structures for the use of cauterization devices and haptic learning for proper tissue manipulation.5-7 Our team has combined novel synthesis methods of conductive thermoplastic polymerization and 3-dimensional-printed cervical spine models to produce a layered biomimetic simulation that provides cost-effective and anatomically accurate education for neurosurgical trainees (Video 1). This is accomplished through virtual modeling and layered simulator construction methods by placing the individual polymer layers according to anatomic location of the simulated in vivo structures. The consistency of the thermoplastics can be tailored according to the desired soft tissue structures (skin, fat, fascia, muscle) according to the degree of polymerization. This cost-effective simulation was designed to represent the material and biomechanical properties of the cervical spine cortico-cancellous interface, as well as individual soft tissue components with specific anatomic details of muscle tendinous and ligamentous insertion. These features allow for representative start-to-finish surgical simulation that has not yet been made widely available to neurosurgical training programs.

Ex vivo virtual and 3D printing methods for evaluating an anatomy-based spinal instrumentation technique for the 12th thoracic vertebra.

INTRODUCTION: Three-dimensional printing and virtual simulation both provide useful methods of patient-specific anatomical modeling for assessing and validating surgical techniques. A combination of these two methods for evaluating the feasibility of spinal instrumentation techniques based on anatomical landmarks has not previously been investigated. MATERIALS AND METHODS: Nineteen anonymized CT scans of the thoracic spine in adult patients were acquired. Maximum pedicle width and height were recorded, and statistical analysis demonstrated normal distributions. The images were converted into standard tessellation language (STL) files, and the T12 vertebrae were anatomically segmented. The intersection of two diagonal lines drawn from the lateral and medial borders of the T12 transverse process (TP) to the lateral border of the pars and inferolateral portion of the TP was identified on both sides of each segmented vertebra. A virtual screw was created and insertion into the pedicle on each side was simulated using the proposed landmarks. The vertebral STL files were then 3D-printed, and 38 pedicles were instrumented according to the individual posterior landmarks used in the virtual investigation. RESULTS: There were no pedicle breaches using the proposed anatomical landmarks for insertion of T12 pedicle screws in the virtual simulation component. The technique was further validated by additive manufacturing of individual T12 vertebrae and demonstrated no breaches or model failures during live instrumentation using the proposed landmarks. CONCLUSIONS: Ex vivo modeling through virtual simulation and 3D printing provides a powerful and cost-effective means of replicating vital anatomical structures for investigation of complex surgical techniques.

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.

3-Dimensionally Printed Biomimetic Surgical Simulation-Operative Technique of a Transforaminal Lumbar Interbody Fusion: 2-Dimensional Operative Video.

We present a surgical video highlighting the technical demonstration and microsurgical anatomy of an L4-5 transforaminal lumbar interbody fusion utilizing a combination of thermoplastic polymers and 3-dimensional printing technology to create a biomimetic lumbar spine surgical simulator. The posterior elements of L4-5 and the inferior portion of L3 are exposed in their entirety, including the transverse processes in order to identify the appropriate landmarks for pedicle screw insertion. The interspinous ligament of L4-5 is removed, and an interlaminar spreader is used to distract the facet joint. An inferior L4 facetectomy is performed for local autograft harvesting. The L4 and L5 pedicles are skeletonized to completely open the foramen in order to ensure that the exiting nerve root will not be compromised during cage insertion. The ligamentum flavum is then removed, exposing the common thecal sac and L5 traversing root. The L4 exiting nerve root is then identified, completing Kambin's triangle and location of the disc space. The disc is incised, and a combination of punches and curettes are used to completely remove the disc. After an interbody trial is used to assess the proper cage size, the cage is packed with graft and inserted into the midline of the disc space. Pedicle screws are then placed using an anatomic freehand technique, and intraoperative fluoroscopy is performed in order to evaluate the instrumentation and interbody position. If a contralateral decompression is required, a facet-sparing technique is performed in order to preserve bony surface for the fusion. Patient consent was not required for this simulation video.

The importance of teaching clinical anatomy in surgical skills education: Spare the patient, use a sim!

Anatomical knowledge is a key tenet in graduate medical and surgical education. Classically, these principles are taught in the operating room during live surgical experience. This puts both the learner and the patient at a disadvantage due to environment, time, and safety constraints. Educational adjuncts such as cadaveric courses and surgical skills didactics have been shown to improve resident confidence and proficiency in both anatomical knowledge and surgical techniques. However, the cost-effectiveness of these courses is a limiting factor and in many cases prevents implementation within institutional training programs. Anatomical simulation in the form of "desktop" three-dimensional (3D) printing provides a cost-effective adjunct while maintaining educational value. This article describes the anatomical and patient-centered approach that led to the establishment of our institution's 3D printing laboratory for anatomical and procedural education. Clin. Anat. 32:124-127, 2019. © 2019 Wiley Periodicals, Inc.

Freehand C2 Laminar Screw Placement: Technical Note and Operative Video.

The placement of C2 laminar screws is a safe and useful method of axis fixation. The freehand method of screw placement was originally described by Wright et al., and requires detailed knowledge of the C2 posterior element anatomy, relationship to vital neurovascular structures, and technical acumen. The current evidence, surgical anatomy and technical details of screw insertion are investigated and highlighted in this manuscript and surgical video.

How I do it: tapered rod placement across the cervicothoracic junction for augmented posterior constructs.

BACKGROUND: Posterior instrumentation techniques are commonly employed for cervicothoracic fixation. The pedicles of the upper thoracic vertebrae can typically accommodate larger diameter screws than the subaxial cervical vertebrae. In many construct systems, this requires the use of a tapered rod, which can be technically challenging to place. METHOD: Using a three-dimensionally printed biomimetic spine simulator, we illustrate the stepwise process of instrumentation and tapered rod placement across the cervicothoracic junction (CTJ). CONCLUSION: Tapered rod systems can augment the biomechanical stability of cervicothoracic constructs. Ease of rod placement across the CTJ hinges upon a systematic method of instrumentation.

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.