Final answer:
The phrase pertains to medical positioning devices that elevate the body from the clavicle to the iliac crests to offload weight from the abdomen and thorax. The clavicle is a key component of the pectoral girdle, which supports upper limb movement and transfers force to the thorax.
Step-by-step explanation:
The phrase 'x2 placed lengthwise under the axilla and along the sides of the chest from the clavicle to iliac crests' refers to a medical practice that involves positioning support materials or devices under the arms (axilla) and along the sides of the chest. These supports span from the clavicle, an S-shaped bone that lies horizontally across the front of the thorax just above the first rib, down to the iliac crests, which are the top ridges of the hip bones.
In a medical setting such placement would be to provide elevation and relief by raising the weight of the body off of the abdomen and thorax potentially aiding in patient comfort or treatment. The pectoral girdle which is made up of the clavicle and scapula transfers force from the upper limbs to the thorax. It is crucial in facilitating movement and providing support for the actions of the upper limbs.