How to build a PENG model

Background

The PENG block is an easy, safe and reliable ultrasound guided nerve block that provides pain control for injuries located to the hip joint, above the IT line. It is a relatively new block, that has the potential benefit of preserving the quadricep strength, allowing early ambulation. 

Despite the growing use of the PENG block, the commercial simulation models for training are expensive, are not easily available, and are not reliable when looking at the anatomy representation and needle navigation. 

This PENG block model is inexpensive, easy to build, reliable and long lasting; it’s a great way to teach physicians how to identify the anatomy and navigate the in-plane needle approach. 

Materials

Step by Step 

1- Glue the piece of flat braid rope to the plastic pelvis. The rope is going to function as the psoas tendon, and it will be the main target of the PENG block. The correct location of the psoas tendon is in the pelvic rim, between the iliopubic eminence and the anterior inferior iliac spine. 

2- Secure the plastic hip joint to the plastic container. You can screw the distal end of the femur to the wall of the container, make sure that the pelvis is placed at the right angle, and that it’s completely inside the container (so it will be completely covered by gelatin). Use the glue gun to cover the screws to prevent leakage in the future.

3- Make the gelatin. I use a special recipe for the gelatin. It’s more concentrated than usual, and it contains isopropyl alcohol as a preservative. 

In a bowl mix: 300 g of Beef gelatin, 1,600 ml of warm tap water (no need to boil the water), and 100 ml of rubbing alcohol. Use a hand mixer to dissolve the gelatin until it has no lumps. With the help of a skimmer, remove all the bubbles from the mix. 

4- Pour the gelatin mix into the plastic container with the hip attached. Depending on the size of the container, you might need to repeat this process multiple times. 

5- Once the hip is completely covered with gelatin, make sure there are no bubbles left in the mix, and put the container in the fridge overnight. It will be ready to use the next morning. 

6- To use the model, cover the surface with a thin layer of water. No need to use ultrasound gel. 

Hot tips 

• Only use 100% pure beef gelatin. Gelatin mixes that contain sugar or other ingredients will not be as firm and as long lasting as the one recommended in this recipe. 
• Bubbles are the worst enemy of ultrasound models. Make sure you remove all of them before putting the mix in the fridge. If the mix cools down too fast, more bubbles will be trapped in the gelatin. Take extra time skimming for bubbles, and tap the container to bring the bubbles afloat. 
• Always keep the model covered with a thin layer of cold tap water. The model can last in the fridge for several months, make sure it is always covered with water so it doesn’t dry out. 
• Over time you will see some needle tracks, pouring water and “massaging” the gelatin can help reduce the marks. If the damage is too extensive, you can scoop out the piece of gelatin, warm it up in the microwave, and patch the model with the same gelatin. 
•  Do not put the whole model in the microwave. Remember we used screws to attach the bone to the container. 
• You can re-use the gelatin for a different project. Simply scoop all the gelatin out of the container, warm up until it becomes liquid, and put in a different container. 

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