Here we created a high fidelity 3D printed task trainer derived from CT scans of normal human anatomy The task trainers created using this protocol, help in performing all critical aspects of a chosen task or procedure, various anatomically correct models can be created with this protocol. It's important to find a CT scan containing the desired anatomic section for the model we are creating, as part of the process used to transform the anatomic scans into 3D models it's important to close the natural openings in the bone to create a final product that permits the addition of features to hold the bone in the correct orientation and to have a space for the simulated marrow. To begin, confirm the correct triangle normal orientation of the imported SDL files, if the triangle orientation is incorrect flip the triangle normal by clicking select, modify and select all.
Next, click select, then edit and flip models to eliminate the unwanted structures and refine the models, to create the task trainer, click on select then select the triangles on the undesired structures and click edit and discard. Select the edit and plane card tool to crop the model to fit within the confines of the 3D printer build volume. Reduce the computational overhead by clicking on select and double clicking anywhere on the mesh to select the entire mesh, then select edit and reduce.
For reduced target, reduce the triangle budget under approximately 10, 000 faces. Once the triangles of the mesh around the defect are selected click on select, then select edit and erase and fill, to improve the surface holes and irregularities. Export and save the finished models using the SDL file type, open the Autodesk Fusion 360 software select insert and then insert mesh command to import the SDL files of bone and tissue models in the workspace as a mesh.
For converting the imported meshes into B-rep Solids disabled the Fusion 360 timeline, reduce the number of triangles in the target mesh to less than 10, 000, select the imported mesh body, then right click to open the menu and select the mesh to B wrap option. After the meshes have been converted to B wrap solids resume the fusion 360 timeline and modify the solid to create the task trainers mold by splitting the rectangular solid along the long axis of the tissue B wrap. Select two to three locations for support pins and place the pre designed assembly group components, to fix the task trainer's bones, import and position a bone plug onto the open marrow space of the bone B rep to prevent tissue media from entering the marrow space and draining the simulated bone marrow.
Generate an opening of four to six centimeters through the molds in the space represented by the tissue B rep solid for pouring the liquid tissue media into the mold, perform the mirror of the objects to make the task trainer for the isolateral side. Once the components of the pre designed assembly groups are positioned to fix the bones in space click bullion combined to either add or cut the various assembly groups in the models. Select the desired body within the workspace and right click, then select Save as STL to export the final components for printing, position the STL file on the bed of the 3D printer and orient the bone vertically.
For printing user raft full support material, a 0.4 millimeter nozzle layer height at 0.2 millimeters with four top and bottom layers, three perimeter shells infill at 20%and hot end temperature of 210 degrees Celsius. Orient the mold components with the tissue surface facing up and print without a raft, set the layer height at 0.3 millimeters infill at 15%and use full support material. Arrange the support pins and other components to minimize support material, print all pin support parts with a raft and set the layer height at 0.2 millimeters and infill at 20%Print the threaded components without support material at a reduced speed, once each component's parameters are selected, prepare and export the G code file generated by the software to SD card.
Open the 3D printer software select the saved G code file from the SD card and 1.75 millimeter polylactic acid 3D printer media filament for printing. Measure the gelatin cilium husk fiber chlorhexidine solution and sodium hypochlorite, to prepare the tissue media and set aside heat one liter of water to 85 degrees Celsius. Add the heated water in a mixing container several times larger than the volume of the ingredients while vigorously shaking the tissue medium solution, add the measured ingredients one by one.
Heat the mixture in a water bath at 71 degrees Celsius for a minimum of four hours for dissipating the bubbles, prepare the simulated bone marrow solution by measuring 100 grams of cold water, 100 grams of ultrasound gel and five milliliters of red food color, then thoroughly mix the ingredients. Spray the inner surfaces of the mold with a non silicone based releasing agent, secure the bone using support pins to maintain the correct position within the tissue space. Then secure the bone to the bottom of the mold and assemble the mold, verify the position of the bone plug to prevent the tissue medium from entering the marrow space during pouring.
Position the mold with the opening facing up and pour 46 degrees Celsius warm tissue medium into the mold cavity. Secure any leakage of the tissue medium from the mold by spraying it with an inverted air duster canister, transfer the filled mold to four degrees Celsius for a minimum of six hours or until the tissue medium has been set. Disassemble the mold and removed the task trainer and support pins remove the bone plug, fill the simulated bone marrow solution in the marrow space and replace the bone plug.
Store the task trainer in a plastic bag at four degrees Celsius or minus 20 degrees Celsius until use. Once the task trainer reaches room temperature instruct the trainees to place the IO needle and aspirate the simulated bone marrow solution. Next, disassemble the task trainers to recover the tissue medium and the bones, disassemble the task trainer and place the gelatin into a container to be remelted for additional use, the model can be reformed and the gel once melted can be reused to create another model.
This protocol was used for modeling and printing the three-dimensional tissue mold and the tissue structures surrounding the skeletal element, using the CT scan of a patient's left knee joint the designed tibia resulted in a very close replica after printing. An opening made to expose the tissue cavity facilitated the pouring of the tissue medium, the mold was designed with two supporting pin assembly groups to support and suspend the bone structures within the tissue cavity. The task trainer was customized for the humorous and tibia using an opaque and transparent tissue medium which allows varying levels of visualization of skeletal structures or landmarks.
The anatomical similarity was achieved between the CT scan data used to create the task trainer and the fully assembled humorous task trainers with respect to bone thickness, skin depth and tendon groove the time and cost required to print the top of the mold were highest followed by the bottom of the mold, the bones and the hardware. When 3D printing the molds, we have found it's important to use a strong adhesive to prevent warping at the base. Another critical aspect is the use of a releasing spray applied to the inner service of the mold prior to adding the gel.
This prevents the gel from sticking to the 3D printed material. These trainers permit skill transfer from the training environment to the clinical environment because of their anatomic similarity with patients, repetition helps a learner to perform the critical steps of a procedure.
