Prehospital Trauma Life Support (PHTLS) Practice Test

What is the earliest site for intraosseous infusion in an adult?

1. Anterior tibia, just above the tibial tuberosity

2. Anterior fibula

3. Anterior tibia, just below the tibial tuberosity

4. Posterior fibula

The correct answer is: Anterior tibia, just below the tibial tuberosity

The correct answer identifies the anterior tibia, just below the tibial tuberosity, as the earliest site for intraosseous infusion in adults. This location is chosen because of several anatomical and practical reasons. The tibia at this site is easily accessible, and the bone is relatively flat, which provides a good area for insertion without risking damage to surrounding structures. Additionally, the anterior aspect of the tibia offers a thick cortex, allowing for proper penetration and stability of the intraosseous needle. By selecting a site just below the tibial tuberosity, the provider minimizes the risk of injuring the growth plate in children while providing optimal access in adults. In contrast, while the anterior tibia just above the tibial tuberosity and the anterior fibula may seem like potential sites, they are less ideal for adult intraosseous infusions due to anatomical considerations such as proximity to the patellar tendon or shallow bone structure. The posterior fibula is generally not used in emergency settings due to more challenging access, increased risk of complications, and the likelihood of surrounding neurovascular structures being damaged during the procedure. Thus, the choice of the tibia just below the tibial tuberosity provides the best combination of accessibility, safety