Background/Purpose: Certain ultrasound (US)-guided procedures may be integral to the diagnosis and management of arthritis. US-guided carpal tunnel (CT), flexor tendon sheath (FTS), and hip injections are more accurate than landmark-guided injections, but they can be more challenging to perform. Soft tissue phantom models simulating anatomic areas give trainees the opportunity to practice. However, cadaver-based models, commercial phantoms, and homemade models require special handling. Affordable, accessible, and soft tissue consistency type phantom models are needed. The tofu phantom model has been used to simulate scenarios of basic categories of US-guided procedures. In this study we use a Tofu-Pasta-Cardstock (TPC) phantom model to simulate challenging scenarios of avoiding neurovascular structures (CT), navigating a superficial narrow target (FTS), and navigating a deep angle (hip).The purpose of this study is to assess improvements to learner confidence in performing CT, FTS and hip US-guided injections after receiving instruction using a practical TPC phantom anatomic simulation model.

Methods: Dried pasta, such as rigatoni, bucatini, and fettuccine (simulating transverse carpal ligament, arteries, and bony contour, respectively), and cardstock (simulating the hip joint) were used for anatomic representation (Figure 1). Locations of insertion within the tofu were approximated to simulate the location and scale of real-world anatomy. Tofu blocks were submerged under water to improve echogenicity of the tofu and to avoid the problem of phantom needle tracks encountered in existing models (Figure 2).Prior to the hands-on training workshop, participants in a beginner/intermediate US course underwent a 20-minute lecture regarding US-guided procedure techniques pertinent to each region. With a learner-to-instructor ratio of 5:1, each participant rotated for 15 minutes through the 3 tofu models, guiding the needle to the target site with sonographic guidance. Immediate feedback related to handling of the syringe, proper ergonomics, US image optimization, and needle approach to the targeted injection site were provided by the instructor. Post workshop, participants were invited to complete a survey accessed via Redcap QR code.

Results: Out of 35 participants, 68.6% responded. 70.8% had less than 1 year of US-guided injection experience. Pre and post workshop confidence of participants increased 75%, 87.5%, and 79% in their US-guided CT, FTS, and hip injection skills, respectively. 58.3% of participants felt that the models were easy to use and that they were likely to recreate this model for personal practice. The TPC models remained intact for the full 90 minutes with at least 5 learners and 1 instructor using each model with multiple needle passes.

Conclusion: The novel combination of tofu, dried pasta, and cardstock is effective in improving learner confidence in their US-guided CT, hip and FTS injection skills and demonstrates many advantages compared to existing phantom models. This accessible and affordable model can simulate challenging injections commonly encountered in rheumatology by demonstrating structures to avoid, depth adjustments and more precise placement of the needle tip.

Figure 1. A) Materials needed for set up. B) Dried pasta approximated and arranged prior to insertion into the tofu. C) Multiple tofu pasta cardstock models can be produced relatively quickly. D) Cardstock inserted into tofu to simulate the hip joint.

Figure 2. A) TPC model, B) corresponding US image, and C) patient example of carpal tunnel injection. D) TPC model, E) corresponding US image, and F) patient example of flexor tendon sheath injection. G) TPC model, H) corresponding US image, and I) patient example of hip injection. White solid arrow = transverse carpal ligament/rigatoni, yellow arrowhead = needle, a = artery/bucatini, FH = femoral head/cardstock, FN = femoral neck/cardstock, FT = flexor tendon/bucatini, MN = median nerve/spaghetti.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/east-meets-west-a-novel-tofu-pasta-cardstock-phantom-model-for-teaching-ultrasound-guided-procedures/