Final answer:
The preferred intraosseous (IO) insertion site is the tibia, specifically the proximal tibia below the knee due to its easy accessibility and status as the main weight-bearing bone of the lower leg.
Step-by-step explanation:
The preferred site for intraosseous (IO) insertion is the tibia. The tibia, also known as the shin bone, is the medial and larger bone of the leg and is the main weight-bearing bone of the lower leg. The proximal tibia, located just below the knee, is particularly suitable for IO access due to its size, easy accessibility, and minimal overlying tissue, making it the most common site for emergency IO insertion when intravenous access is not possible.
The femur is the body's second-longest bone and transfers the weight from the femur to the foot, while the fibula, also known as the calf bone, is a site for muscle attachment and forms the lateral part of the ankle joint but does not bear weight. The humerus can be used as an alternative IO insertion site, particularly at the proximal humerus, but it is generally considered after the tibia.