Anywhere there is a potential for contamination or pollution of the drinking water system, a backflow prevention device is required. Devices can be small and simple, such as an anti-siphon vacuum breaker (AVB) on a hose spigot (Photo), or large and complex, like those used on fire sprinkler systems (Photo).
An avulsion fracture occurs when a muscle or tendon is pulled so hard at the spot where it attaches to the bone that it tears a small piece of bone away. Avulsion fractures can occur on any part of the body, but they are most common in the ankles, hips, and elbows.
1 In an avulsion fracture, a ligament or tendon and the piece of bone it attaches to pull away from the main bone. 2  In an impacted fracture, the broken ends of a bone drive into each other.  In a shear fracture, the bone splits in two when a force causes it to move in two different directions.