Generally, an external fixator is mounted quite securely to the bone, and can withstand mild contact, any positioning of the body, and oftentimes even weightbearing immediately after surgery. In fact, it is often more comfortable to pick up the leg by grabbing the fixator, rather than holding the leg itself.he fixator is composed or one or more metal bars and rings, which in turn connect to a child via metal pins and wires. By gradually manipulating the fixator on the outside, we can carefully control the position of the bones and joints on the inside.
Habitat and Distribution. Pin this Image. Green sea urchins used to live in cold waters of the sub Polar Regions. They live in Northern cooler part of the Pacific and Atlantic Ocean. Some also live in the Arctic too. The sea animal can be found in rocky sea beds. They often live in the low depth tidal zones.
Sea otters, sunflower stars and California sheephead prey on purple sea urchins. Sea otter predation on purple sea urchins helps protect kelp forests from destruction. Sea otters that regularly eat purple sea urchins are easily detectedâtheir bones and teeth turn sea-urchin purple! In the intertidal zone, purple sea urchins decorate themselves with shells, rocks and pieces of algae. Scientists think this behavior protects urchins from drying out, getting eaten by gulls or being damaged by the sun's ultraviolet rays. When a sea star strives to get near an urchin, the urchin moves its spines aside and lets the sea star's arm get really close. Then the ...