IDEA Series: 3D-printed pediatric lumbar puncture trainer

Pediatric lumbar puncture trainers are less available than adult trainers; most are the newborn size and quite expensive. Due to age-based practice patterns for fever diagnostic testing, most pediatric lumbar punctures are performed on young infants, and residents have fewer opportunities to perform lumbar punctures on older children.¹ Adult lumbar puncture trainers have been created using a 3D-printed spine and ballistics gel, which allows for ultrasound guidance.² No previous model has been described for pediatric lumbar puncture.

The Innovation

We created a pediatric lumbar puncture trainer with realistic landmarks using a 3D-printed pediatric lumbar spine and ballistics gel. We included the iliac crests in our model to facilitate teaching trainees to locate the L4 spinous process by palpating the hips. The model allows for ultrasound guidance. A connection to an IV bag allows opening pressure adjustment and measurement.

The Learners

The model can be used by anyone wanting to practice pediatric lumbar puncture by landmarks or with ultrasound guidance, including opening pressure measurement. This includes medical students, residents, fellows, and faculty.

Equipment

• 3D printer
• Ballistics gel
• Ballistics gel dye
• Silicone straws
• Plastic child torso dress form mannequin
• Multipurpose adapter
• Gaffer tape
• IV bag

Description of the Innovation

We took the following steps to create the 3D printed spine with iliac crests:

• We used the open-source software 3D Slicer to extract the lumbar spine from a CT abdomen and pelvis of a pediatric patient (we used a 6-year-old patient). 3D Slicer loads DICOM files directly. It allows DICOM files to be exported as an .nrrd file, which is a single file that is stripped of patient identifiers. This makes working with the data easier and more secure. Once the area of interest is selected, 3D Slicer can export a 3D print-ready .stl file. There are numerous YouTube videos that demonstrate the use of 3D Slicer. We found these two especially helpful:

 

• We used Autodesk Meshmixer to add cylindrical columns between vertebral bodies and between the sacrum and iliac wings so that the model will not lose its shape when the melted ballistics gel is poured into the mold. Meshmixer is also free software that can also be used to label the model’s vertebral bodies.

• We printed the 3D model on a Prusa I3 MK3S printer using 1.75mm vanilla-color polylactic acid (PLA) filament.

You can print the pediatric lumbar spine model yourself using our .stl file. Once you have the 3D printed spine, complete the model as follows:

1. Create the spinal column: Insert a 13 mm diameter silicone straw into the spine to create a spinal column. Place a rubber stopper on the lower end of the straw, and the multipurpose adapter on the upper end, so that the column can be attached to an IV bag.
2. Create the torso of the model, which includes the following steps.
   • Create a mold from the plastic child torso dress form mannequin. Cut the midsection from the mannequin and use gaffer tape to create dams on the top and bottom.
   • Suspend the 3D printed lumbar spine in the form using screws, allowing the desired amount of space between the spinous process and the skin.

1. • Melt the ballistics gel and dye in an electric slow cooker (the dye will obscure the spinous processes, so the melted ballistics gel dye should be mixed into the melted gel before pouring).
   • Pour in the melted ballistics gel and allow it to cure overnight.

3. Attach an IV bag to the spinal column. The opening pressure is set to the height of the bag and can be adjusted by raising or lowering the bag.

4. Practice ultrasound assistance by marking a grid on the lumbar area using a dry erase marker. Spinous processes should be clearly visible on ultrasound.

The total cost of our model was $55, $25 of which covered the dress form torso that we used for the mold. Since the mold is reusable, this would bring the price of each subsequent trainer to $30. We created a second, clear version without dye to allow learners to visualize the path of the needle as it enters the subarachnoid space. This helps trainees better understand procedure mechanics and assists in troubleshooting complications.

A video of the trainer’s creation and use can be found here:

Lessons Learned

• We initially printed the lumbar spine model without cylindrical supports. This caused the spine to deform when we poured in the melted ballistics gel. The cylindrical supports solved this problem.
• We first used duct tape to dam the mold, but the duct tape did not stay attached when the heated gel was poured and also left behind residue. The gaffer tape worked better and was easier to remove from the cured gel. We recommend using ample gaffer tape to ensure that the poured gel does not escape from the mold.
• The writing from a dry erase marker was easily removable from the trainer.

Educational Theory

The trainer allows for deliberate practice of the micro-skills involved in pediatric lumbar puncture and opening pressure measurement.³ The model can be stored in a readily accessible area close to the emergency department and used for just-in-time training.⁴ It can be left in a community space and used as a coaching tool.⁵ When a learner self-identifies the need to improve pediatric lumbar puncture skills, they can seek out a more experienced practitioner to act as a coach and provide feedback while practicing on the trainer.

Closing Thoughts

This model is useful for training programs that have access to a 3D printer and want to create opportunities to teach pediatric lumbar puncture with opening pressure measurement without breaking the bank.

References

1. Glatstein MM, Zucker-Toledano M, Arik A, Scolnik D, Oren A, Reif S. Incidence of traumatic lumbar puncture: experience of a large, tertiary care pediatric hospital. Clin Pediatr. 2011;50(11):1005-1009. PMID: 21622691
2. Odom M, Gomez JR, Danelson KA, Sarwal A. Development of a Homemade Spinal Model for Simulation to Teach Ultrasound Guidance for Lumbar Puncture. Neurocrit Care. 2019;31(3):550-558. PMID: 31313141
3. Ericsson KA, Anders Ericsson K. Deliberate Practice and Acquisition of Expert Performance: A General Overview. Academic Emergency Medicine. 2008;15(11):988-994. PMID: 18778378
4. Thomas AA, Uspal NG, Oron AP, Klein EJ. Perceptions on the Impact of a Just-in-Time Room on Trainees and Supervising Physicians in a Pediatric Emergency Department. Journal of Graduate Medical Education. 2016;8(5):754-758. PMID: 28018542
5. LeBlanc C, Sherbino J. Coaching in emergency medicine. CJEM. 2010;12(06):520-524. PMID: 21073779

 

 

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