Damon, Aaron

AbstractIntroductionThree‐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 MethodsNineteen 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.ResultsThere 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.ConclusionsEx 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.

AbstractThree‐dimensional (3D) printing has revolutionized individualized medicine for patient‐specific anatomical modeling and surgical planning. The surge of investigations in model creation for preoperative assessments and patient education has demonstrated improvements in both operative factors and patient satisfaction. In addition, recent technologic advances in 3D printing techniques have provided a resource to create visually pleasing models with chromatic cues for segmentation of adjacent structures. Despite these advances, an important consideration that has yet to be addressed is the quality of representation of the not only the form of structures created, but also the functional relationships of each structure. Jean François Fernel (1497–1558 AD) recognized a similar trend in anatomic innovation over 500 years ago, and sparked a series of texts that challenged the superficial anthropocentric views of the time and led to the foundation of physiologic principles that shaped modern medical philosophy. Accurately generating anatomical structures are directly related to discerning true physiologic function, and a comprehensive understanding of both is essential to hold accountability in fidelity for individualized 3D printing.

Abstract 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.

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.

Abstract 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.